TY - CONF TI - A Model of Copper Electrodeposition from Cyanide Electrolyte: II Current Distribution on a Disk Electrode AU - Fedkiw, P. AU - Dudek, D. T2 - 1997 SUR/FIN Proceedings C2 - 1997/6// C3 - 1997 SUR/FIN Proceedings DA - 1997/6// PY - 1997/6// ER - TY - CONF TI - Composite Electrolytes Based on Fumed Silica, PEO Oligomers, and Lithium Salts for Application in Rechargeable Lithium Batteries AU - Fedkiw, P. AU - Fan, J. T2 - Symposium on Lithium Polymer Batteries A2 - Broadhead, J. A2 - Scrosati, B. C2 - 1997/// C3 - Proceedings of the Symposium on Lithium Polymer Batteries CY - San Antonio, Tex. DA - 1997/// PY - 1996/// ER - TY - CHAP TI - Real-time kinetic analysis of hydrogen abstraction and etching reactions using pulsed-gas PECVD of amorphous and microcrystalline silicon AU - Srinivasan, E AU - Parsons, GN AU - Wagner, S AU - Hack, M AU - Schiff, EA AU - Schropp, R AU - Shimizu, I T2 - Amorphous and Microcrystalline Silicon Technology - 1997 PY - 1997/// VL - 467 SP - 501-506 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000071462000075&KeyUID=WOS:000071462000075 ER - TY - CHAP TI - Comparison of conventional and self-aligned a-Si:H thin film transistors AU - Yang, CS AU - Read, WW AU - Arthur, CB AU - Parsons, GN AU - Fulks, RT AU - Slobodin, DE AU - Yuzuriha, TH T2 - Flat Panel Display Materials Iii PY - 1997/// VL - 471 SP - 179-184 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1997BJ69K00027&KeyUID=WOS:A1997BJ69K00027 ER - TY - CHAP TI - Wavelength sensitivity in polymer photodegradation AU - Andrady, A.L. T2 - Polymer Analysis Polymer Physics A2 - Andrady, A.L. T3 - Advances in polymer science PY - 1997/// SP - 47–94 PB - Springer - Verlag SN - 3540612181 0387612181 9783540612186 9780387612188 SV - 128 ER - TY - JOUR TI - Accelerated aerobic biodegradability of paperboard AU - Andrady, A.L. AU - Song, Y. T2 - Proceedings of the American Chemical Society (ACS) Division of Polymeric Materials Science and Engineering DA - 1997/// PY - 1997/// VL - 76 SP - 470–471 ER - TY - RPRT TI - Pavement Marking Materials: Assessing Environment-Friendly Performance AU - Andrady, Anthony L. A3 - National Academy Press: Transportation Research Board, National Research Council, DA - 1997/// PY - 1997/// M1 - 393 M3 - NCHRP Report PB - National Academy Press: Transportation Research Board, National Research Council, SN - 393 UR - http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_392.pdf ER - TY - BOOK TI - Polymer Analysis Polymer Physics AU - Andrady, A.L. AU - Narasimhan, B. AU - Pascault, J.-P. AU - Pasch, H. AU - Peppas, N.A. AU - Rozenberg, B.A. AU - Williams, R.J.J. T2 - Advances in Polymer Science DA - 1997/// PY - 1997/// DO - 10.1007/3-540-61218-1 M1 - 128 PB - Springer SN - 9783540612186 9783540683742 UR - http://dx.doi.org/10.1007/3-540-61218-1 ER - TY - JOUR TI - Elastic behavior of chitosan films AU - Andrady, Anthony L. AU - Xu, P. T2 - Journal of Polymer Science Part B: Polymer Physics AB - The thermoelastic behavior and equilibrium stress–strain properties of chitosan films lightly crosslinked with gluteraldehyde and swollen with water were studied. Precautions were taken to preclude changes in the swelling ratio of swollen sample films during the experiment. The results indicate that at relatively low extensions the elastic behavior of the biopolymer is entropic in origin. The equilibrium stress–strain isotherms of chitosan did not obey Mooney–Rivlin equation because of sharp increases in stress with extension ratio at high extensions. This is attributed mainly to interchain hydrogen-bonded interactions, but a possible contribution due to strain–induced crystallization cannot be ruled out. © 1997 John Wiley & Sons, Inc. DA - 1997/2// PY - 1997/2// DO - 10.1002/(sici)1099-0488(199702)35:3<517::aid-polb10>3.0.co;2-k VL - 35 IS - 3 SP - 517-521 J2 - J. Polym. Sci. B Polym. Phys. LA - en OP - SN - 0887-6266 1099-0488 UR - http://dx.doi.org/10.1002/(sici)1099-0488(199702)35:3<517::aid-polb10>3.0.co;2-k DB - Crossref KW - elasticity KW - chitosan KW - biopolymer KW - stress-strain ER - TY - JOUR TI - Viscosity Reduction Of Hydraulic Fracturing Fluids Through Enzymatic Hydrolysis AU - Tayal, Akash AU - Kelly, Robert M. AU - Khan, Saad A. T2 - SPE Journal AB - Abstract High viscosity formulations of guar are used as fracturing fluids to enhance oil and gas production. Following fracturing, these fluids are hydrolyzed and flushed out of the well to provide outflow for oil or gas. Enzymes offer an effective and environmentally benign method for hydrolyzing the guar to a low viscosity fluid. In this study, we used steady shear rheometry to elicit fundamental information on the capabilities and limitations of enzymes. The effect of commercial and new thermostable enzymes on polymer viscosity was investigated in terms of process variables such as temperature of hydrolysis, pH of solution and enzyme concentration. The commercial enzyme was most effective in degrading the guar at slightly acidic conditions and up to 60°C. Above 60°C, the extent of hydrolysis of guar solutions decreased. With increasing temperature, enzymatic activity increased but enzyme stability decreased and this balance was critical in determining the extent of viscosity reduction. Experiments using preheated enzyme also revealed lower viscosity reduction, suggesting that most of the hydrolysis occurs during the enzyme heat up, following which the enzymes deactivate rapidly. Similar experiments with the thermostable enzyme system demonstrated high levels of viscosity reduction at elevated temperatures (up to 85°C) and limited viscosity reduction at ambient conditions. This is suggestive of enhanced capability of this enzyme system at elevated temperatures compared to that of the commercial system. Experiments using purified enzymes from both enzyme systems also revealed that the largest reduction in viscosity of guar solutions occurs with endo-β-D mannanase, the enzyme cleaving the bonds between the mannose backbone units. DA - 1997/6/1/ PY - 1997/6/1/ DO - 10.2118/38432-pa VL - 2 IS - 02 SP - 204-212 LA - en OP - SN - 1086-055X 1930-0220 UR - http://dx.doi.org/10.2118/38432-pa DB - Crossref ER - TY - JOUR TI - Purification and Characterization of a Proteasome from the Hyperthermophilic Archaeon Pyrococcus furiosus AU - Bauer, M W AU - Bauer, S H AU - Kelly, R M T2 - Applied and Environmental Microbiology AB - A 640-kDa proteasome consisting of (alpha) (25-kDa) and (beta) (22-kDa) subunits, and with a temperature optimum of 95(deg)C, was purified from crude cell extracts of a hyperthermophilic archaeon, Pyrococcus furiosus. Although this is the fourth member of the kingdom Euryarchaeota (and the first hyperthermophile) found to contain a proteasome, none has been identified among the members of the kingdom Crenarchaeota. DA - 1997/3// PY - 1997/3// DO - 10.1128/aem.63.3.1160-1164.1997 VL - 63 IS - 3 SP - 1160-1164 J2 - Appl Environ Microbiol LA - en OP - SN - 0099-2240 1098-5336 UR - http://dx.doi.org/10.1128/aem.63.3.1160-1164.1997 DB - Crossref ER - TY - JOUR TI - Physical modulation of intracellular signaling processes by locational regulation AU - Haugh, J.M. AU - Lauffenburger, D.A. T2 - Biophysical Journal AB - Recent observations in the field of signal transduction suggest that where a protein is located within a cell can be as important as its activity measured in solution for activation of its downstream pathway. The physical organization of the cell can provide an additional layer of control upon the chemical reaction networks that govern ultimately perceived signals. Using the cytosol and plasma membrane as relevant compartmental distinctions, we analyze the effect of relocation on the rate of association with a membrane-associated target. We quantify this effect as an enhancement factor E in terms of measurable parameters such as the number of available targets, molecular diffusivities, and intrinsic reaction rate constants. We then employ two simple yet relevant example models to illustrate how relocation can affect the dynamics of signal transduction pathways. The temporal profiles and phase behavior of these models are investigated. We also relate experimentally observable aspects of signal transduction such as peak activation and the relative time scales of stimulus and response to quantitative aspects of the relocation mechanisms in our models. In our example schemes, nearly complete relocation of the cytosolic species in the signaling pair is required to generate meaningful activation of the model pathways when the association rate enhancement factor E is as low as 10; when E is 100 or greater, only a small fraction of the protein must be relocated. DA - 1997/5// PY - 1997/5// DO - 10.1016/s0006-3495(97)78846-5 VL - 72 IS - 5 SP - 2014-2031 ER - TY - JOUR TI - An Investigation into the Importance of Polymer-Matrix Miscibility Using Surfactant Modified Matrix-assisted Laser Desorption/Ionization Mass Spectrometry AU - Kassis, Camille M. AU - DeSimone, Joseph M. AU - Linton, Richard W. AU - Lange, Gary W. AU - Friedman, Robert M. T2 - Rapid Communications in Mass Spectrometry AB - Sample preparation, namely finding a suitable matrix–analyte combination, has been one of the most important concerns in using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for synthetic polymers. Herein we report the novel use of surfactants in the polymer sample preparation procedure. Specifically, three nonionic surfactants were investigated for MALDI analysis of poly(methyl methacrylate) (PMMA). This approach resulted in major enhancements in the PMMA molecular ion signals with dithranol as the matrix. The results illustrate the importance of polymer–matrix miscibility in optimizing MALDI investigations. © 1997 John Wiley & Sons, Ltd. DA - 1997/8/30/ PY - 1997/8/30/ DO - 10.1002/(sici)1097-0231(19970830)11:13<1462::aid-rcm44>3.0.co;2-2 VL - 11 IS - 13 SP - 1462-1466 J2 - Rapid Commun. Mass Spectrom. LA - en OP - SN - 0951-4198 1097-0231 UR - http://dx.doi.org/10.1002/(sici)1097-0231(19970830)11:13<1462::aid-rcm44>3.0.co;2-2 DB - Crossref ER - TY - JOUR TI - The Morphology of Block Copolymer Micelles in Supercritical Carbon Dioxide by Small-Angle Neutron and X-ray Scattering AU - Londono, J. D. AU - Dharmapurikar, R. AU - Cochran, H. D. AU - Wignall, G. D. AU - McClain, J. B. AU - Betts, D. E. AU - Canelas, D. A. AU - DeSimone, J. M. AU - Samulski, E. T. AU - Chillura-Martino, D. AU - Triolo, R. T2 - Journal of Applied Crystallography AB - Above its critical point, carbon dioxide forms a super-critical fluid, which promises to be an environmentally responsible replacement for the organic solvents traditionally used in polymerizations. Many lipophilic polymers such as polystyrene (PS) are insoluble in CO 2 , though polymerizations may be accomplished via the use of PS-fluoropolymer stabilizers, which act as emulsifying agents. Small-angle neutron and X-ray scattering have been used to show that these molecules form micelles with a CO 2 -phobic PS core and a CO 2 -philic fluoropolymer corona. When the PS block was fixed in length and the fluorinated corona block was varied, the number of block copolymer molecules per micelle (six to seven) remained constant. Thus, the coronal block molecular weight exerts negligible influence on the aggregation number, in accordance with the theoretical predictions of Halperin, Tirrell & Lodge [ Adv. Polym. Sci. (1992), 100 , 31–46]. These observations are relevant to understanding the mechanisms of micellization and solubilization in supercritical fluids. DA - 1997/10/1/ PY - 1997/10/1/ DO - 10.1107/s0021889897002446 VL - 30 IS - 5 SP - 690-695 J2 - J Appl Cryst OP - SN - 0021-8898 UR - http://dx.doi.org/10.1107/s0021889897002446 DB - Crossref ER - TY - JOUR TI - Propagation Rate Coefficients of Styrene and Methyl Methacrylate in Supercritical CO2 AU - van Herk, Alex M. AU - Manders, Bart G. AU - Canelas, Dorian A. AU - Quadir, Murat A. AU - DeSimone, Joseph M. T2 - Macromolecules AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPropagation Rate Coefficients of Styrene and Methyl Methacrylate in Supercritical CO2Alex M. van Herk, Bart G. Manders, Dorian A. Canelas, Murat A. Quadir, and Joseph M. DeSimoneView Author Information Eindhoven University of Technology, Laboratory of Polymer Chemistry, P.O. Box 513, 5600 MB Eindhoven, The Netherlands University of North Carolina at Chapel Hill, Department of Chemistry, CB# 3290, Venable and Kenan Laboratories, Chapel Hill, North Carolina 27599-3290 Cite this: Macromolecules 1997, 30, 16, 4780–4782Publication Date (Web):August 11, 1997Publication History Received12 March 1997Revised11 June 1997Published online11 August 1997Published inissue 1 August 1997https://doi.org/10.1021/ma9703416Copyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views401Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (90 KB) Get e-AlertsSUBJECTS:Lasers,Monomers,Organic compounds,Polymers,Styrenes Get e-Alerts DA - 1997/8// PY - 1997/8// DO - 10.1021/ma9703416 VL - 30 IS - 16 SP - 4780-4782 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma9703416 DB - Crossref ER - TY - JOUR TI - Emulsion Stabilization and Flocculation in CO2. 2. Dynamic Light Scattering AU - Yates, M. Z. AU - O'Neil, M. L. AU - Johnston, K. P. AU - Webber, S. AU - Canelas, D.A. AU - Betts, D.E. AU - DeSimone, J.M. T2 - Macromolecules AB - Dynamic light scattering (DLS) was used to investigate steric stabilization and flocculation of dilute poly(2-ethylhexyl acrylate) (PEHA, Mw = 92K) emulsions in liquid CO2 at 25 °C by monitoring changes in droplet size over time at various CO2 densities. Two steric stabilizers were investigated: a homopolymer, poly(1,1-dihydroperfluorooctyl acrylate) (PFOA, Mw = 1 × 106), and a block copolymer, polystyrene (Mn = 4.5K g/mol)-b-PFOA (Mn = 25K). For a concentration of 0.03 wt %, aggregates of PS-b-PFOA were observed in CO2 with an average hydrodynamic diameter of approximately 80 nm and a polydispersity index of 0.2−0.3 from the method of cumulants. Critical flocculation densities (CFDs) of PEHA emulsions were determined by lowering the CO2 density at constant temperature to induce flocculation. The CFDs of the emulsions agree closely with the ϑ point density of PFOA in CO2 for both the homopolymer and block copolymer stabilizers. Above the CFD, the emulsions have an average droplet size of 400−600 nm and are stable over several hours. With shear, the average droplet size of emulsions stabilized with PS-b-PFOA decreases with time because of shear-enhanced flocculation, and subsequent sedimentation of the flocculated droplets. The flocculation of the emulsion is attributed to a depletion mechanism induced by PS-b-PFOA aggregates in solution. DA - 1997/8// PY - 1997/8// DO - 10.1021/ma961694s VL - 30 IS - 17 SP - 5060–5067 SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma961694s ER - TY - CHAP TI - Polymerizations in Liquid and Supercritical Carbon Dioxide AU - Canelas, Dorian A. AU - DeSimone, Joseph M. T2 - Metal Complex Catalysts Supercritical Fluid Polymerization Supramolecular Architecture A2 - Canelas, D.A. A2 - DeSimone, J.M. A2 - Harada, A. A2 - Ihara, E. A2 - Mashima, K. A2 - Nakamura, A. A2 - Nakayama, Y. A2 - Yasuda, H. T3 - Advances in Polymer Science PY - 1997/// DO - 10.1007/3-540-68442-5_3 SP - 103–140 PB - Springer Berlin SN - 9783540626992 9783540684428 SV - 133 UR - http://dx.doi.org/10.1007/3-540-68442-5_3 ER - TY - JOUR TI - Extraction of a hydrophilic compound from water into liquid CO2 using dendritic surfactants AU - Cooper, A. I. AU - Londono, J. D. AU - Wignall, G. AU - McClain, J. B. AU - Samulski, E. T. AU - Lin, J. S. AU - Dobrynin, A. AU - Rubinstein, M. AU - Burke, A. L. C. AU - Fréchet, J. M. J. AU - DeSimone, J. M. T2 - Nature DA - 1997/9// PY - 1997/9// DO - 10.1038/38706 VL - 389 IS - 6649 SP - 368-371 J2 - Nature LA - en OP - SN - 0028-0836 1476-4687 UR - http://dx.doi.org/10.1038/38706 DB - Crossref ER - TY - JOUR TI - XPS analysis of poly[(3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)] film surfaces exposed to an allylamine low-pressure plasma AU - Mas, André AU - Jaaba, Hassan AU - Schué, François AU - Belu, Anna M. AU - Kassis, Camille M. AU - Linton, Richard W. AU - Desimone, Joseph M. T2 - Macromolecular Chemistry and Physics AB - Abstract Homogeneous and stable layers were deposited through allylamine plasma polymerization (75 W, 100 Pa, 15 min) onto poly[(3‐hydroxybutyric acid)‐ co ‐(3‐hydroxyvaleric acid)] (91 : 9 wt.‐%) (P(HB‐ co ‐9%HV)) film surfaces, XPS analysis using take‐off angles of 20° and 70° and performed 10 days and 20 days after plasma treatment gives information on the composition (in atom%) of the modified surface: C, 62.74; N, 19.60; O, 17.65. The unexpected oxygen percentage is weaker if argon plasma pretreatment (25 W, 40 Pa, 5 min) is applied. Then, a succinct mechanism is proposed. The study of changes in element ratios and binding energy values shows that the majority of incorporated functional groups seem to be amide and imine groups. DA - 1997/11// PY - 1997/11// DO - 10.1002/macp.1997.021981133 VL - 198 IS - 11 SP - 3737-3752 J2 - Macromol. Chem. Phys. OP - SN - 1022-1352 1521-3935 UR - http://dx.doi.org/10.1002/macp.1997.021981133 DB - Crossref ER - TY - JOUR TI - Emulsion Polymerization in a Hybrid Carbon Dioxide/Aqueous Medium AU - Quadir, Murat A. AU - Snook, Rodd AU - Gilbert, Robert G. AU - DeSimone, Joseph M. T2 - Macromolecules AB - The development of a new reaction medium is reported, based on a biphasic mixture of carbon dioxide and water for emulsion polymerizations: a surfactant-free aqueous emulsion polymerization of methyl methacrylate using potassium persulfate under a varying head pressure of CO2 (0−350 bar) at 75 °C. The resulting polymer is a stable latex with particles of submicron size. The effect of CO2 on polymerization is relatively small, until there is a significant change at high CO2 pressure. This is seen by examining the molecular weight distribution in the form of the log(number distribution), P(M) (readily obtained by GPC). At pressures of 140 bar and below, the P(M) show the form expected for chain-stopping events dominated by transfer and by diffusion-controlled termination. At 280 bar, ln P(M) is significantly steeper than its lower-pressure counterpart at relatively low conversion (45%). This is attributed to swelling by supercritical CO2 reducing the viscosity of the particles, allowing more rapid termination. DA - 1997/10// PY - 1997/10// DO - 10.1021/ma970259a VL - 30 IS - 20 SP - 6015-6023 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma970259a DB - Crossref ER - TY - JOUR TI - Dispersion polymerization of methyl methacrylate in supercritical carbon dioxide: Influence of helium concentration on particle size and particle size distribution AU - Hsiao, Yu-Ling AU - Desimone, Joseph M. T2 - Journal of Polymer Science Part A: Polymer Chemistry AB - Dispersion polymerizations of methyl methacrylate utilizing poly(1,1,-dihydroperfluorooctyl acrylate) as a steric stabilizer in supercritical carbon dioxide (CO2) were carried out in the presence of helium. Particle size and particle size distribution were found to be dependent on the amount of inert helium present. Particle sizes ranging from 1.64 to 2.66 μm were obtained with various amounts of helium. Solvatochromic investigations using 9-(α-perfluoroheptyl-β,β-dicyanovinyl)julolidine indicated that the solvent strength of CO2 decreases with increasing helium concentration. This effect was confirmed by calculations of Hildebrand solubility parameters. Dispersion polymerization results indicate that PMMA particle size can be attenuated by the amount of helium present in supercritical CO2. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 2009–2013, 1997 DA - 1997/7/30/ PY - 1997/7/30/ DO - 10.1002/(sici)1099-0518(19970730)35:10<2009::aid-pola16>3.0.co;2-k VL - 35 IS - 10 SP - 2009-2013 J2 - J. Polym. Sci. A Polym. Chem. LA - en OP - SN - 0887-624X 1099-0518 UR - http://dx.doi.org/10.1002/(sici)1099-0518(19970730)35:10<2009::aid-pola16>3.0.co;2-k DB - Crossref ER - TY - JOUR TI - Cationic Dispersion Polymerizations in Liquid Carbon Dioxide AU - Clark, M. R. AU - Kendall, J. L. AU - DeSimone, J. M. T2 - Macromolecules AB - The successful cationic dispersion polymerization of styrene in liquid carbon dioxide using amphiphilic block copolymers is reported. Vinyl ether block copolymers consisting of a CO2-philic fluorinated segment and a poly(methyl vinyl ether) anchoring segment were employed to stabilize the growing polystyrene (PS) particles. The effect of stabilization in these polymerizations on molar mass, molar mass distribution, and polymer yield was studied as a function of temperature and surfactant composition. Scanning electron microscopy confirmed the formation of PS particles ranging in size from 300 nm to 1 μm in diameter. DA - 1997/10// PY - 1997/10// DO - 10.1021/ma9619344 VL - 30 IS - 20 SP - 6011-6014 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma9619344 DB - Crossref ER - TY - JOUR TI - Photoinduced graft polymerization of styrene onto polypropylene substrates AU - Li, Yuhua AU - Desimone, Joseph M. AU - Poon, Chi-Duen AU - Samulski, Edward T. T2 - Journal of Applied Polymer Science AB - The photochemical grafting of styrene onto polypropylene (PP) using benzophenone (BP) and benzoin ethyl ether (BEE) as photosensitizers is described. The effects of various parameters (such as monomer and photosensitizer concentration, reaction time, and solvent) on percent grafting were studied. We found that BP is a very efficient photosensitizer for the grafting of styrene onto PP surfaces. Unlike BEE, BP does not initiate nongrafting homopolymerization reactions in solution which compete with grafting reactions. This is advantageous over other photosensitizers since homopolymer formed in solution can interfere with the grafting reaction as well complicate sample preparation and purification. The graft copolymers obtained using both BP and BEE were characterized by high resolution 1H-NMR, optical microscopy and swelling studies. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 883–889, 1997 DA - 1997/5/2/ PY - 1997/5/2/ DO - 10.1002/(sici)1097-4628(19970502)64:5<883::aid-app8>3.0.co;2-l VL - 64 IS - 5 SP - 883-889 J2 - J. Appl. Polym. Sci. LA - en OP - SN - 0021-8995 1097-4628 UR - http://dx.doi.org/10.1002/(sici)1097-4628(19970502)64:5<883::aid-app8>3.0.co;2-l DB - Crossref KW - photochemical grafting KW - styrene KW - polypropylene KW - benzophenone KW - benzoin ethyl ether ER - TY - JOUR TI - Modification de Surface de Poly (Hydroxybutyrate-co-9% Hydroxyvalerate) Par Polymerisation Par Plasma d'Alcool Allylique AU - Mas, A. AU - Jaaba, H. AU - Schue, F. AU - Belu, A.M. AU - Kassis, C.M. AU - Linton, R.W. AU - Desimone, J.M. T2 - European Polymer Journal AB - La polymérisation par plasma d'alcool allylique conduit au dépôt d'un film minceà la surface de P(HB-co-9% HV). L'enrichissement en oxygène est faible mais se traduit par une augmentation des carbones de types CO, C-OC, C-OH déterminée par ESCA et une mouillabilité supérieure par rapport au matériau non traité. La mouillabilité diminue avec l'augmentation de la température et du temps de stockage après traitement puis se stabilise mais elle reste fixeà −20°C. L'interprétation est basée sur la réorientation des groupes polaires en surface et l'existence d'un dépôt non réticulé dont la valeur de la température de transition vitreuse serait comprise entre −20 et 25°C.) Allyl alcohol plasma polymerization permits to obtain a thin deposited film on to P(HB-co-9% HV) surface. The oxygen atomic increase is weak but gives an increase of Cls in CO, C-OC, C-OH bonds which is determinate by XPS analysis and a wettability greater than that of the non-treated material. The wettability decreases with storage temperature and time after treatment then it is stable. However it remains constant at − 20°C. The interpretation is supported by polar groups motions on the surface and the formation of a non-crosslinked deposited film whose the glass temperature value would be situated between −20 and 25°C. © 1997 Elsevier Science Ltd. All rights reserved DA - 1997/3// PY - 1997/3// DO - 10.1016/s0014-3057(96)00154-1 VL - 33 IS - 3 SP - 331–337 SN - 0014-3057 UR - http://dx.doi.org/10.1016/s0014-3057(96)00154-1 ER - TY - JOUR TI - Poly(Hydroxybutyrate-co-9% Hydroxyvalerate) Film Surface Modification by Ar, O2, H2,O/O2, H2O, and H2O2 Plasma Treatment AU - Mas, A. AU - Jaaba, H. AU - Schue, F. AU - Belu, A. M. AU - Kassis, C. AU - Linton, R. W. AU - Desimone, J. M. T2 - Journal of Macromolecular Science, Part A AB - Abstract We modified poly(hydroxybutyrate-co-9% hydroxyvalerate) film surfaces with Ar, O2, H2O/O2, H2O, and H2O2 vapor plasma treatments. We measured the grafted oxygen concentration by XPS analyses and the wettability by a θH2O contact angle method. Comparison between these various plasma treatments seems to indicate a better surface wettability correlated to C-OH bonds obtained with H2O and H2O2 plasma than with Ar and O2 plasma which incorporate oxygen atoms in C˭O bonds more easily. DA - 1997/1// PY - 1997/1// DO - 10.1080/10601329708014935 VL - 34 IS - 1 SP - 67–79 SN - 1060-1325 1520-5738 UR - http://dx.doi.org/10.1080/10601329708014935 ER - TY - JOUR TI - A Direct Deposition Method for Coupling Matrix-assisted Laser Desorption/Ionization Mass Spectrometry with Gel Permeation Chromatography for Polymer Characterization AU - Kassis, Camille E. AU - DeSimone, Joseph M. AU - Linton, Richard W. AU - Remsen, Edward E. AU - Lange, Gary W. AU - Friedman, Robert M. T2 - Rapid Communications in Mass Spectrometry AB - Matrix-assisted laser desorption/ionization (MALDI) measurements of polymeric materials of narrow polydispersity provide molecular weight measurements that agree closely with those from conventional tools such as gel-permeation chromatography (GPC). However, materials that have a broader molecular weight distribution (polydispersity) > 1.1) have been shown to diminish the accuracy of the MALDI results. In a recent effort to overcome this limitation, some researchers have utilized GPC prior to MALDI analysis to collect fractions with narrower molecular weight distributions. In our research, the GPC eluent was spray deposited onto a rotating matrix-coated substrate and the resulting polymer ‘trail’ was characterized directly by MALDI. Specifically, molecular weight information was determined using various points along poly(methyl methacrylate) sample ‘trails’ deposited on a matrix of trans-3-indoleacrylic acid. The overall number-average molecular weight (M n) and molecular weight distribution (MWD) for each of the samples were calculated. The Mn values are in fairly good agreement with manufacturer's values, though the MWD values determined by MALDI are narrower. © 1997 John Wiley & Sons, Ltd. DA - 1997/6/30/ PY - 1997/6/30/ DO - 10.1002/(sici)1097-0231(19970630)11:10<1134::aid-rcm910>3.0.co;2-0 VL - 11 IS - 10 SP - 1134-1138 J2 - Rapid Commun. Mass Spectrom. LA - en OP - SN - 0951-4198 1097-0231 UR - http://dx.doi.org/10.1002/(sici)1097-0231(19970630)11:10<1134::aid-rcm910>3.0.co;2-0 DB - Crossref ER - TY - JOUR TI - Observation of an Inverse Kinetic Isotope Effect in a Co(III)-Catalyzed Polymerization of Ethylene AU - Tanner, Martha J. AU - Brookhart, M. AU - DeSimone, J. M. T2 - Journal of the American Chemical Society AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunicationObservation of an Inverse Kinetic Isotope Effect in a Co(III)-Catalyzed Polymerization of EthyleneMartha J. Tanner, M. Brookhart, and J. M. DeSimoneView Author Information Department of Chemistry University of North Carolina at Chapel Hill Chapel Hill, North Carolina 27514 Cite this: J. Am. Chem. Soc. 1997, 119, 32, 7617–7618Publication Date (Web):August 13, 1997Publication History Received24 April 1997Published online13 August 1997Published inissue 1 August 1997https://doi.org/10.1021/ja971300sCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views568Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (137 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Alkyls,Isotope effects,Metals,Monomers,Transition states Get e-Alerts DA - 1997/8// PY - 1997/8// DO - 10.1021/ja971300s VL - 119 IS - 32 SP - 7617-7618 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja971300s DB - Crossref ER - TY - JOUR TI - Flow system and 9.5 GHz microwave resonators for time-resolved and steady-state electron paramagnetic resonance spectroscopy in compressed and supercritical fluids AU - Dukes, Katerina E. AU - Harbron, Elizabeth J. AU - Forbes, Malcolm D. E. AU - DeSimone, Joseph M. T2 - Review of Scientific Instruments AB - An apparatus for the electron paramagnetic resonance (EPR) detection of stable and transient free radicals in pressurized liquids and supercritical fluids is described. The construction of a quartz EPR sample cell capable of withstanding pressures up to 3000 psi (204 atm) and the components of a high pressure flow system are explained and illustrated. In order to accommodate the thick-walled, high pressure sample tube, two X-band (9.5 GHz) microwave cavities were fabricated. One is a brass, cylindrical TE011 cavity for time-resolved (direct detection) EPR experiments where field modulation was not necessary, and the other is a silver wire-wound cylindrical TE011 cavity, mounted in a quartz support tube. The wire-wound cavity allows for simultaneous light excitation and field modulation for steady-state EPR. Both cavities are fitted with tunable end plates to facilitate tuning at X band in the face of large frequency shifts when the sample tube is introduced to the resonator and to allow for operation with smaller sample tubes at ambient pressure. Microwave coupling, flow optimization, and UV-light access for both cavities are described, and sample spectra in both time-resolved and steady-state modes are reported. DA - 1997/6// PY - 1997/6// DO - 10.1063/1.1148149 VL - 68 IS - 6 SP - 2505-2510 J2 - Review of Scientific Instruments LA - en OP - SN - 0034-6748 1089-7623 UR - http://dx.doi.org/10.1063/1.1148149 DB - Crossref ER - TY - JOUR TI - Dispersion Polymerizations of Styrene in Carbon Dioxide Stabilized with Poly(styrene-b-dimethylsiloxane) AU - Canelas, Dorian A. AU - DeSimone, Joseph M. T2 - Macromolecules AB - Herein we report the use of poly(styrene-b-dimethylsiloxane) block copolymers as steric stabilizers for dispersion polymerizations of styrene in a carbon dioxide continuous phase. It was demonstrated that the anchor-soluble balance (ASB) of the stabilizer has a dramatic effect on both the progress of the reaction and the morphology of the resulting polystyrene (PS) colloid. When a stabilizer with an appropriate ASB is employed, the initial concentrations of styrene, stabilizer, and helium have substantial effects on the resulting size and dispersity of the colloidal particles. Dispersion polymerizations carried out under a series of different pressures (143−439 bar) resulted in variations in the conversion, molecular weight, and PS particle diameter, suggesting that the reaction is extremely sensitive to the density of the continuous phase. An investigation of the progress of the reaction as a function of time at two different temperatures revealed that the average molecular weight increases gradually over the course of the reaction. Finally, control reactions in heptane solvent were not as successful as those conducted in CO2 suggesting that the plasticization of the polymer particles by CO2 facilitates diffusion of monomer to the growing chain ends. DA - 1997/9// PY - 1997/9// DO - 10.1021/ma970579u VL - 30 IS - 19 SP - 5673-5682 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma970579u DB - Crossref ER - TY - JOUR TI - Emulsion Stabilization and Flocculation in CO2. 1. Turbidimetry and Tensiometry AU - O'Neill, M. L. AU - Yates, M. Z. AU - Harrison, K. L. AU - Johnston, K. P. AU - Canelas, D. A. AU - Betts, D. E. AU - DeSimone, J. M. AU - Wilkinson, S. P. T2 - Macromolecules AB - The stabilization and flocculation of emulsions of poly(2-ethylhexyl acrylate) (PEHA) in liquid and supercritical carbon dioxide (SC-CO2) with the homopolymer poly(1,1-dihydroperfluorooctyl acrylate) (PFOA), the diblock copolymer polystyrene-b-PFOA, and the triblock copolymer PFOA-b-poly(vinyl acetate)-b-PFOA were quantified by turbidimetry and measurements of interfacial tension. Upon decreasing the CO2 density, a distinct change in emulsion stability occurs at the critical flocculation density (CFD). Steric stabilization by the homopolymer PFOA is due to a small number of adsorbed segments and a large number of segments in loops and tails as determined by measurements of the PEHA−CO2 interfacial tension. Below the CFD, flocculation is irreversible due to bridging by the high molecular weight PFOA chains. PS-b-PFOA adsorbs much more strongly to the PEHA−CO2 interface than the other two stabilizers. Consequently, it provides the greatest resistance to emulsion flocculation, both above and below the CFD, and the most reversible flocculation. For all stabilizers studied, the CFD correlates very well with the estimated ϑ point for PFOA in bulk CO2. DA - 1997/8// PY - 1997/8// DO - 10.1021/ma9616930 VL - 30 IS - 17 SP - 5050-5059 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma9616930 DB - Crossref ER - TY - JOUR TI - Stabilized Polymer Microparticles by Precipitation with a Compressed Fluid Antisolvent. 1. Poly(fluoro acrylates) AU - Mawson, Simon AU - Johnston, Keith P. AU - Betts, Doug E. AU - McClain, Jim B. AU - DeSimone, Joseph M. T2 - Macromolecules AB - Poly(1,1-dihydroperfluorooctyl acrylate) (poly(FOA)) based stabilizers greatly reduce, and in some cases eliminate, flocculation of amorphous poly(methyl methacrylate) (PMMA) and polystyrene (PS) microparticles formed by precipitation into liquid CO2 at 23 °C. The microparticle stabilization mechanism is explained in terms of the stabilizer−CO2 phase behavior, the spray characteristics, and the interfacial activity of the stabilizer. Compared with the homopolymer poly(FOA), the diblock copolymer PS-b-poly(FOA) produces smaller and more spherical primary particles (0.1−0.3 μm) and also prevents flocculation at lower stabilizer concentrations. These differences are due to the greater interfacial activity of PS-b-poly(FOA). Steric stabilization commences in the jet on the order of several tenths of milliseconds and continues for seconds throughout the precipitator. With the use of a coaxial nozzle, precipitation is delayed and the stabilizers become even more effective at preventing flocculation. DA - 1997/1// PY - 1997/1// DO - 10.1021/ma961048t VL - 30 IS - 1 SP - 71-77 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma961048t DB - Crossref ER - TY - JOUR TI - Time-Resolved EPR Study of a 1,9-Flexible Biradical Dissolved in Liquid Carbon Dioxide. Observation of a New Spin-Relaxation Phenomenon:  Alternating Intensities in Spin-Correlated Radical Pair Spectra AU - Avdievich, Nikolai I. AU - Dukes, Katerina E. AU - Forbes, Malcolm D. E. AU - DeSimone, Joseph M. T2 - The Journal of Physical Chemistry A AB - X-band (9.5 GHz) time-resolved electron paramagnetic resonance (TREPR) spectra of a 1,9-acyl−alkyl biradical were obtained at room temperature in benzene and in liquid (950 psi) carbon dioxide (CO2) solutions. The spin exchange interaction (J) in this biradical is negative and larger in magnitude than the hyperfine interaction (q). This leads to the observation, in both solvents, of spin-correlated radical pair (SCRP) spectra which are net emissive. Spectra obtained at later delay times (>1.5 μs) in CO2 exhibit alternating intensities of their SCRP transitions due to spin relaxation but do not show any significant change in line width. The same effect is observed in benzene, but on a slower time scale. Q-band (35 GHz) experiments in benzene showed that the phenomenon was found to be both field and temperature dependent. It is also chain-length dependent, being much stronger in short biradicals (1,1′ (lauryl amido)-propyl ammonium chloride (LAPAC)/DPE-15>DPE-15>DDBS-Na>LAPAC. On the other hand, the order of emulsion stability is as follows: LAPAC>DDBS-Na/DPE-15>DPE-15>DDBS-Na. The effect of the aqueous phase salinity up to 5% NaCl concentration on the stability of asphalt emulsions stabilized by different surfactant solutions systems is discussed. © 1997 SCI. DA - 1997/7// PY - 1997/7// DO - 10.1002/(SICI)1097-4660(199707)69:3<350::AID-JCTB699>3.0.CO;2-7 VL - 69 IS - 3 SP - 350-356 SN - 0268-2575 KW - asphalt emulsions KW - emulsion stability KW - emulsifiers KW - interfacial tension KW - colloid systems ER - TY - CONF TI - Mechanical alloying of PET and PET/Vectra blends AU - Balik, C. M. AU - Bai, C. AU - Koch, C. C. AU - Spontak, R. J. AU - Saw, C. K. A2 - R. M. Briber, C. C. Han A2 - Peiffer, D. G. C2 - 1997/// C3 - Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings) CN - QD381.9.S87 M67 1997 DA - 1997/// VL - 461 SP - 39 PB - Warrendale, PA: Materials Research Society ER - TY - JOUR TI - X-ray microscopy and NEXAFS spectroscopy of macrophase-separated random block copolymer/homopolymer blends AU - Smith, AP AU - Laurer, JH AU - Ade, HW AU - Smith, SD AU - Ashraf, A AU - Spontak, RJ T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTX-ray Microscopy and NEXAFS Spectroscopy of Macrophase-Separated Random Block Copolymer/Homopolymer BlendsArchie P. Smith, Jonathan H. Laurer, Harald W. Ade, Steven D. Smith, Arman Ashraf, and Richard J. SpontakView Author Information Departments of Materials Science & Engineering and Physics, North Carolina State University, Raleigh, North Carolina 27695, and Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239 Cite this: Macromolecules 1997, 30, 3, 663–666Publication Date (Web):February 10, 1997Publication History Received20 August 1996Revised13 November 1996Published online10 February 1997Published inissue 1 February 1997https://doi.org/10.1021/ma9612687Copyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views143Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (158 KB) Get e-AlertsSUBJECTS:Colloids,Copolymers,Energy,Transmission electron microscopy,X-rays Get e-Alerts DA - 1997/2/10/ PY - 1997/2/10/ DO - 10.1021/ma9612687 VL - 30 IS - 3 SP - 663-666 SN - 0024-9297 ER - TY - JOUR TI - Salting-in behavior of isotropic and anisotropic aqueous hydroxypropylcellulose solutions AU - Prevysh, VA AU - Wang, BC AU - Khan, SA AU - Spontak, RJ T2 - COLLOID AND POLYMER SCIENCE DA - 1997/3// PY - 1997/3// DO - 10.1007/s003960050082 VL - 275 IS - 3 SP - 284-287 SN - 0303-402X KW - salting-in KW - hydroxypropylcellulose KW - rheology KW - chiral nematic mesophase KW - liquid crystal ER - TY - CONF TI - Phase behavior of triblock copolymers upon incorporation of nonparent, midblock-associating additives AU - Laurer, J. H. AU - Mulling, J. F. AU - Bukovnik, R. AU - Spontak, Richard A2 - R. M. Briber, C. C. Han A2 - Peiffer, D. G. C2 - 1997/// C3 - Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings) CN - QD381.9.S87 M67 1997 DA - 1997/// DO - 10.1557/proc-461-69 VL - 461 SP - 69–74 PB - Warrendale, PA: Materials Research Society ER - TY - JOUR TI - Phase behavior of complex diblock copolymer blends: A transmission electron microscopy study AU - Fung, JC AU - Kane, L AU - Smith, SD AU - Sedat, JW AU - Agard, DA AU - Spontak, RJ T2 - PROCEEDINGS OF THE 13TH INTERNATIONAL CONFERENCE ON DEFECTS IN INSULATING MATERIALS - ICDIM 96 DA - 1997/// PY - 1997/// DO - 10.4028/www.scientific.net/msf.239-241.179 VL - 239- SP - 179-184 SN - 0255-5476 KW - block copolymers KW - microphase-ordering KW - gyroid KW - polymer blends KW - electron microtomography ER - TY - JOUR TI - Macromolecular self-assembly in dilute sequence-controlled block copolymer/homopolymer blends AU - Laurer, JH AU - Ashraf, A AU - Smith, SD AU - Samseth, J AU - Spontak, RJ T2 - SUPRAMOLECULAR SCIENCE AB - Conventional block copolymers consist of two long contiguous monomer sequences (‘blocks’) that can, in the same fashion as low-molar-mass surfactants, self-assemble into various microstructural elements (e.g., micelles at low copolymer concentrations) to minimize repulsive contacts in the presence of a parent homopolymer. In this work, we explore the existence of segment-specific interactions, as well as the possibility of tailoring these blend morphologies (and producing altogether new ones), with novel sequence-controlled block copolymers. These copolymers are comprised of at least one block that is a random segment composed of both constituent monomer species. Transmission electron microscopy is employed here to examine the bilayered membranes and channel structures that form in two different series of such copolymers in dilute copolymer/homopolymer blends. DA - 1997/// PY - 1997/// DO - 10.1016/S0968-5677(96)00048-X VL - 4 IS - 1-2 SP - 121-126 SN - 0968-5677 KW - block copolymers KW - micelles KW - bilayered membranes ER - TY - CONF TI - Effect of additive constraint on the morphological and mechanical properties of triblock copolymer blends AU - Kane, L. AU - Norman, D. A. AU - White, S. A. AU - Spontak, Richard A2 - R. M. Briber, C. C. Han A2 - Peiffer, D. G. C2 - 1997/// C3 - Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings) CN - QD381.9.S87 M67 1997 DA - 1997/// DO - 10.1557/proc-461-75 VL - 461 SP - 75–80 PB - Warrendale, PA: Materials Research Society ER - TY - CONF TI - Conformational and dynamic properties of polymer loops and their mixtures at an impenetrable interface AU - Gulati, H. S. AU - Jones, R. L. AU - Driscoll, D. C. AU - Spontak, Richard AU - Hall, Carol A2 - D. Wirtz, A2 - Halsey, T. C. C2 - 1997/// C3 - Statistical mechanics in physics and biology: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A, 1997 (Materials Research Society symposia proceedings) CN - QC174.7 .S742 1997 DA - 1997/// DO - 10.1557/proc-463-109 VL - 463 SP - 109–114 ER - TY - JOUR TI - The introductory course in materials thermodynamics: Strategies toward improved instructional effectiveness AU - Prebola, J. L. AU - Spontak, R. J. T2 - Journal of Materials Education DA - 1997/// PY - 1997/// VL - 19 IS - 1997 SP - 47 ER - TY - JOUR TI - Self-organization and polyolefin nucleation efficacy of 1,3:2,4-di-p-methylbenzylidene sorbitol AU - Shepard, TA AU - Delsorbo, CR AU - Louth, RM AU - Walborn, JL AU - Norman, DA AU - Harvey, NG AU - Spontak, RJ T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Recent studies have demonstrated that addition of a small quantity of dibenzylidene sorbitol (DBS) to a molten polymer may result in a physical gel if conditions permit the DBS molecules to self-organize into a three-dimensional network composed of highly connected nanofibrils. If the polymer crystallizes, DBS may also serve as a nucleating agent, promoting the formation of spherulites, especially in commercially important polyolefins such as polypropylene. We examine the thermal and mechanical properties, as well as the morphological characteristics, of an isotactic polypropylene copolymer with 3 wt % ethylene upon addition of less than 1 wt % of 1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS). From dynamic rheological measurements, pronounced complex viscosity increases, attributed to MDBS nanofibril network formation, are observed at concentration-dependent temperatures above the melting point of the nucleated copolymer. Transmission electron micrographs of RuO4-stained sections confirm the existence of MDBS nanofibrils measuring on the order of 10 nm in diameter and, at higher concentrations, fibrillar bundles measuring up to about 200 nm across and several microns in length. The addition of MDBS at different concentrations is also found to promote increases in optical clarity, yield strength, tensile strength, and ultimate elongation of modified copolymer formulations. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2617–2628, 1997 DA - 1997/11/30/ PY - 1997/11/30/ DO - 10.1002/(SICI)1099-0488(19971130)35:16<2617::AID-POLB5>3.0.CO;2-M VL - 35 IS - 16 SP - 2617-2628 SN - 0887-6266 KW - dibenzylidene sorbitol KW - polymer crystal nucleation KW - polypropylene KW - clarifying agent ER - TY - PAT TI - Purified Thermococcus barossii DNA polymerase AU - Luhm, R. A. AU - d'Hennezel, O. B. AU - Duffaud, G. D. AU - Jolly, J. F. AU - Kelly, R. M. AU - Ting, E. Y. C2 - 1997/// DA - 1997/// PY - 1997/// ER - TY - JOUR TI - Macromolecular dynamics in extensional flows .2. The evolution of molecular strain AU - Carrington, SP AU - Tatham, JP AU - Odell, JA AU - Saez, AE T2 - POLYMER AB - The opposed jets apparatus has been used to investigate the dynamics of the coil-stretch transition of polymer solutions in an idealized stagnation point extensional flow field. Flow simulations generated fluid strain profiles for different geometries. Assuming a molecular uncoiling model, true birefringence profiles have been converted to molecular strains for closely monodisperse, high molecular weight aPS under θ-conditions. This has enabled macromolecular deformation to be followed as a function of position and residence time. Non-linear hydrodynamic friction FENE dumb-bell simulations give qualitative agreement. Initially, molecular uncoiling is non-affine, consistent with changing hydrodynamic screening on extension. Deformation in a good solvent is more affine. Results are compared with PEO/water to investigate the effect of molecular parameters. The effective extensional viscosity has been ascertained by correction for the area of high molecular extension. The increase in extensional viscosity due to molecular stretching is substantial, of the order of the number of equivalent flexible units in the chain. © 1997 Elsevier Science Ltd. DA - 1997/9// PY - 1997/9// DO - 10.1016/S0032-3861(96)01080-4 VL - 38 IS - 18 SP - 4595-4607 SN - 0032-3861 KW - molecular stretching KW - polymer solutions KW - extensional flow ER - TY - JOUR TI - Environmental management for the future AU - Overcash, M T2 - PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES AB - The field of cleaner technology continues to represent the major new direction for environmental management. Defining cleaner technology or pollution prevention is difficult because the context for use is very diverse. However, a typical definition is ‘All efforts closely related to or influencing manufacturing, that also reduce chemical loss or waste generation.’ Other definitions are described in this paper, as well as a history of pollution prevention in the United States. Economics remain a major driving force for the development and use of pollution prevention alternatives in industries providing goods and services. The tools for achieving cleaner technology are discussed to better understand the challenges to industry in implementing cleaner technology concepts. DA - 1997/7/15/ PY - 1997/7/15/ DO - 10.1098/rsta.1997.0057 VL - 355 IS - 1728 SP - 1299-1307 SN - 1364-503X ER - TY - JOUR TI - A noninvasive study of milk cleaning processes: Calcium phosphate removal AU - Grant, CS AU - Webb, GE AU - Jeon, YW T2 - JOURNAL OF FOOD PROCESS ENGINEERING AB - ABSTRACT High temperature, high pH milk processing results in the formation of mineral rich deposits that are > 70% mineral and < 30% protein by weight. This research investigates the removal of P 32 labeled mixtures of calcium phosphate dihydrate (brushite, CaHPO 4 –2H 2 O) and hydroxyapatite (Ca 5 (PO 4 ) 3 OH) from stainless steel tubes using a solid scintillation technique. Experiments were performed at pH values ranging from 2.86–7.82 and flow rates from 3.8–11.4 L/min. Previous cleaning models are reviewed and a mass transfer model is proposed which, when compared to the experimental results suggests that film removal is due to both dissolution and mechanical effects due to shear stress. A modified first order model is presented which incorporates the effects of the solvent flow rate and pH on decontamination rates. This first order model is in agreement with the experimental results over the range of pH and flow rates investigated. DA - 1997/7// PY - 1997/7// DO - 10.1111/j.1745-4530.1997.tb00419.x VL - 20 IS - 3 SP - 197-230 SN - 0145-8876 ER - TY - JOUR TI - Spatial distribution of gas and solid phases in conical slurry bubble columns AU - Siquier, S AU - Ronchetti, A AU - Calderon, M AU - Llaguno, P AU - Saez, AE T2 - CHEMICAL ENGINEERING COMMUNICATIONS AB - In this work we perform an experimental study of the spatial distribution of phases in slurry bubble columns with conical distributors that have a volume comparable to that of the cylindrical section. Three different distributors were used whose apex angles were 13°, 22° and 34°. In gas-liquid operation, the gas holdups are axially uniform in the cylindrical section and decrease towards the wall, whereas in the conical section they increase towards the inlet. These trends are observed in the three cones for all the operating conditions explored. The solids distributions in the conical sections are qualitatively different depending on whether the operation is semibatch or continuous with respect to the flow of solid-liquid suspension: in semibatch operation, the concentration monotonically increases towards the bottom of the cone and exhibits a slight increase as the wall is approached; in continuous operation, an absolute maximum in solids concentration is obtained at a point located on the wall of the cone and intermediate height. The location of this maximum moves upwards as the total solids content in the column increases and as the apex angle decreases. The maximum in solids concentration signals the most probable site for the onset of solids sedimentation and the presence of low mixing levels and reduced mass transfer rates in a slurry reactor. In the range of conditions explored in the present work, the lowest apex angle (13°) yields a more uniform solids distribution throughout the system DA - 1997/// PY - 1997/// DO - 10.1080/00986449708936600 VL - 159 SP - 173-190 SN - 0098-6445 KW - bubble column KW - sedimentation-dispersion KW - conical distributor KW - tapered column ER - TY - JOUR TI - Selective precipitation of antibody with ligand-modified phospholipids: Effect of lipid chain length AU - Kilpatrick, PK AU - Lisi, JF AU - Carbonell, RG T2 - BIOTECHNOLOGY PROGRESS AB - Abstract The selective precipitation from aqueous solutions of goat polyclonal anti‐biotin antibody (pABA) by complexation with ligand‐modified phospholipids (LMPs) is described. In this study, the effect of varying the acyl chain length of the LMP from six to 18 carbon atoms on the rate and yield of precipitation is detailed. As the acyl chain length increases, the hydrophobic driving force for interaction of ligand‐bound antibody molecules also increases, resulting in a larger yield of precipitated antibody. The rate of selective precipitation, however, is observed to pass through a sharp maximum at an acyl chain length of 10–12 carbon atoms. In the range of target antibody and LMP concentrations studied (1–10 μM), the maximum rates of precipitation are observed for those LMPs in sufficiently low concentrations in aqueous solution to be below their critical micelle concentration (CMC) . The longer chain length LMPs (12–18 carbon atoms at concentrations of 5–10 μM) gave considerably slower rates of precipitation and were all observed to be micellar solutions. The yield of target antibody as a percentage of antibody precipitated was not observed to pass through a maximum, rather all LMPs with acyl chain lengths longer than 12 carbon atoms were observed to give the maximum yield. Thus the optimal structure of an LMP for precipitation of a target antibody corresponds to the maximum chain length (10 carbon atoms) at a concentration level (5–10 μM) which still falls below its CMC. The kinetics of precipitation, as monitored by measuring turbidity, are well modelled by a theory which combines the Mie theory of light scattering with the Smoluchowski theory for the kinetics of precipitation. The maximum rate constants corresponding to Smoluchowski kinetics for precipitating pABA were approximately 25 000–30 000 M −1 s −1 , while the maximum yields were 65–70%. The molecular picture which emerges is one in which the optimal rate is obtained by maximizing hydrophobic driving force for interaction of LMP acyl chains while still maintaining a submicellar state of aggregation. DA - 1997/// PY - 1997/// DO - 10.1021/bp9700521 VL - 13 IS - 4 SP - 446-452 SN - 1520-6033 ER - TY - JOUR TI - Modeling growth of Saccharomyces rosei in cucumber fermentation AU - Passos, FV AU - Fleming, HP AU - Felder, RM AU - Ollis, DF T2 - FOOD MICROBIOLOGY AB - Objectives of this study were to assess the effects of key variables involved in cucumber fermentation on growth of the yeast,Saccharomyces rosei, and to develop a mathematical description of those effects. The growth medium for the studies was cucumber juice. Effects of concentrations of lactic, acetic, and hydrochloric acids and sodium chloride on growth at 30°C were determined in batch culture. Effect of substrate concentration on the specific growth rate was also defined. The specific growth rate decreased from 0.355 h−1at pH 6.0 to 0.189 h−1at pH 3.2. The undissociated form of lactic acid was more inhibitory than that of acetic acid. A predictive equation for specific growth rate was developed for predicting growth ofS. roseiin batch culture. The molar yield of ethanol was 1.75 (±0.07) mM ethanol per mM hexose. Malate was not utilized, and glycerol was produced. The apparent biomass yield under anaerobic condition was 12.2 (±1.3) g cells/mol hexose. Aerobically, the biomass yield was 30.7 g cells/mol hexose. Similar specific growth rates were observed anaerobically (0.358 h−1) and aerobically (0.352 h−1). The predictive model for growth ofS. roseiin cucumber juice should prove useful in modeling the mixed culture (yeast and lactic acid bacteria) fermentation of brined, whole cucumbers. DA - 1997/12// PY - 1997/12// DO - 10.1006/fmic.1997.0118 VL - 14 IS - 6 SP - 533-542 SN - 1095-9998 ER - TY - JOUR TI - Hydrogen transfer between methanogens and fermentative heterotrophs in hyperthermophilic cocultures AU - Muralidharan, V. AU - Rinker, K. D. AU - Hirsh, I. S. AU - Bouwer, E. J. AU - Kelly, Robert T2 - Biotechnology and Bioengineering AB - Interactions involving hydrogen transfer were studied in a coculture of two hyperthermophilic microorganisms: Thermotoga maritima, an anaerobic heterotroph, and Methanococcus jannaschii, a hydrogenotrophic methanogen. Cell densities of T. maritima increased 10-fold when cocultured with M. jannaschii at 85°C, and the methanogen was able to grow in the absence of externally supplied H2 and CO2. The coculture could not be established if the two organisms were physically separated by a dialysis membrane, suggesting the importance of spatial proximity. The significance of spatial proximity was also supported by cell cytometry, where the methanogen was only found in cell sorts at or above 4.5 μm in samples of the coculture in exponential phase. An unstructured mathematical model was used to compare the influence of hydrogen transport and metabolic properties on mesophilic and hyperthermophilic cocultures. Calculations suggest the increases in methanogenesis rates with temperature result from greater interactions between the methanogenic and fermentative organisms, as evidenced by the sharp decline in H2 concentration in the proximity of a hyperthermophilic methanogen. The experimental and modeling results presented here illustrate the need to consider the interactions within hyperthermophilic consortia when choosing isolation strategies and evaluating biotransformations at elevated temperatures. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 268–278, 1997. DA - 1997/// PY - 1997/// DO - 10.1002/(sici)1097-0290(19971105)56:3<268::aid-bit4>3.0.co;2-h VL - 56 IS - 3 SP - 268–278 ER - TY - JOUR TI - High-temperature slurry reactors for synthesis gas reactions .1. Liquid thermal stability AU - Roberts, GW AU - Marquez, MA AU - McCutchen, MS AU - Haney, CA AU - Shin, ID T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - The use of slurry reactors has been limited to reactions that take place at temperatures below about 573 K because many of the liquids that have been used to suspend the solid catalyst are not stable above this temperature. The thermal stability of a number of organic liquids was evaluated at temperatures between 648 and 698 K and at H2 partial pressures of about 7 MPa. Certain saturated and partially-saturated, fused-ring compounds with no alkyl groups or bridges are quite stable at these conditions. Of the compounds tested, tetrahydronaphthalene, tetrahydroquinoline, and decahydronaphthalene were the most stable. Analysis of the liquids at the end of the thermal stability evaluation supports some speculation concerning possible degradation reactions. DA - 1997/10// PY - 1997/10// DO - 10.1021/ie970136e VL - 36 IS - 10 SP - 4143-4154 SN - 0888-5885 ER - TY - JOUR TI - Gas permeability and phase morphology of poly(1-(trimethylsilyl)-1-propyne)/poly(1-phenyl-1-propyne) blends AU - Toy, LG AU - Freeman, BD AU - Spontak, RJ AU - Morisato, A AU - Pinnau, I T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTGas Permeability and Phase Morphology of Poly(1-(trimethylsilyl)-1-propyne)/Poly(1-phenyl-1-propyne) BlendsLora G. Toy, Benny D. Freeman, Richard J. Spontak, Atsushi Morisato, and Ingo PinnauView Author Information Departments of Chemical Engineering and Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 Membrane Technology and Research, Inc., 1360 Willow Road, Suite 103, Menlo Park, California 94025 Cite this: Macromolecules 1997, 30, 16, 4766–4769Publication Date (Web):August 11, 1997Publication History Received22 January 1997Revised19 May 1997Published online11 August 1997Published inissue 1 August 1997https://doi.org/10.1021/ma970091tCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views362Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (146 KB) Get e-AlertsSUBJECTS:Colloids,Interface engineering,Permeability,Selectivity,Transmission electron microscopy Get e-Alerts DA - 1997/8/11/ PY - 1997/8/11/ DO - 10.1021/ma970091t VL - 30 IS - 16 SP - 4766-4769 SN - 0024-9297 ER - TY - JOUR TI - Fluids and fluid mixtures containing square-well diatomics: Equations of state and canonical molecular dynamics simulation AU - Gulati, HS AU - Hall, CK T2 - JOURNAL OF CHEMICAL PHYSICS AB - We present new perturbation theory equations of state for square-well dimer fluids, square-well dimer mixtures, square-well dimer/monomer mixtures and square-well heteronuclear dumbbell fluids. Our first- and second-order perturbation terms are based on Barker and Henderson’s local compressibility approximation and Chang and Sandler’s perturbation theory, respectively. The perturbation approach requires knowledge of the radial distribution functions of the reference hard-dimer fluid and hard dimer/monomer mixture, which are obtained from molecular dynamics simulation. For mixtures we use one fluid mixing rules to approximate the average mixture structure and perturbation parameters. The predictions of the perturbation theory are compared to the compressibility factors obtained from discontinuous canonical molecular dynamics simulation, an adaptation of Anderson’s canonical ensemble molecular dynamics method to the case in which the potential is discontinuous. DA - 1997/9/8/ PY - 1997/9/8/ DO - 10.1063/1.474749 VL - 107 IS - 10 SP - 3930-3946 SN - 0021-9606 ER - TY - JOUR TI - Acquired thermotolerance and stressed-phase growth of the extremely thermoacidophilic Archaeon Metallosphaera sedula in continuous culture AU - Han, C. J. AU - Park, S. H. AU - Kelly, R. M. T2 - Applied and Environmental Microbiology DA - 1997/// PY - 1997/// VL - 63 IS - 6 SP - 2391-2396 ER - TY - JOUR TI - Sorption isotherms for spherical penetrants in facilitating polymeric media using Monte Carlo simulations AU - Sunderrajan, S AU - Hall, CK AU - Freeman, BD T2 - MOLECULAR PHYSICS AB - Grand canonical ensemble Monte Carlo simulations of penetrant sorption in polymeric media have been used to predict sorption isotherms as a function of polymer–penetrant interactions. The polymer is modelled as a collection of hard chains and as a collection of square-well chains, while the penetrant is modelled as hard spheres and as square-well spheres. Partition coefficients have been compared for the different potentials of interaction for stationary and moving polymeric media. Partition coefficients are found to increase with increasing reservoir penetrant pressure and to be higher in moving polymeric media than in stationary polymeric media. Partitioning was studied also as a function of concentration of facilitating sites which have an increased affinity for penetrants. Partition coefficients increased with increasing concentration of facilitating sites. The presence of a second penetrant species of normal affinity is found to affect the partitioning of species with a special affinity for facilitating sites. The partition coefficient for the penetrant species with special affinity for facilitating sites is lower in a mixture than when present as the only component. The partition coefficient of the penetrant species of normal affinity at intermediate mole fractions is higher in a mixture than when present as the only component. DA - 1997/9// PY - 1997/9// DO - 10.1080/002689797170671 VL - 92 IS - 1 SP - 109-116 SN - 0026-8976 ER - TY - JOUR TI - Kinetic model for batch cellulase production by Trichoderma reesei RUT C30 AU - Velkovska, S AU - Marten, MR AU - Ollis, DF T2 - JOURNAL OF BIOTECHNOLOGY AB - A kinetic model for batch cellulase enzyme production by T. reesei from cellulose substrate is constructed from literature concepts and laboratory data. The key concepts included were four: (i) existence of primary and secondary mycelia; (ii) cellulase production by secondary mycelia only; (iii) the adsorption of cellulase (catalyst) on the particulate cellulose (substrate), and (iv) the decline of cellulose reactivity with extent of conversion. The laboratory batch data were biomass (particulate), substrate (particulate cellulose), and product (cellulase enzyme and reducing sugar) concentration vs. time. The kinetic parameters were evaluated simultaneously through a nonlinear fitting routine, and the resultant model is shown to fit the data well. The model's success validates the presumed need to include all four concepts in reactor analysis for cellulase production. DA - 1997/4/25/ PY - 1997/4/25/ DO - 10.1016/S0168-1656(97)01669-6 VL - 54 IS - 2 SP - 83-94 SN - 0168-1656 KW - modeling KW - cellulase production KW - Trichoderma reesei KW - batch cultivation ER - TY - JOUR TI - Hydrogen chemisorption on silica-supported Pt clusters: In situ X-ray absorption spectroscopy AU - Reifsnyder, SN AU - Otten, MM AU - Sayers, DE AU - Lamb, HH T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - Hydrogen chemisorption on small silica-supported Pt clusters was investigated using in situ extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray absorption near-edge structure (XANES) spectroscopy. The clusters were found to exhibit a bulklike Pt first nearest neighbor (NN) distance (2.76 Å) and low disorder while covered by chemisorbed hydrogen. In contrast, bare Pt clusters produced by heating in vacuo at 300 °C are characterized by a contracted Pt NN distance (2.66 Å) and greater disorder. These effects are reversed by re-exposure of the bare Pt clusters to H2 at 25 °C. The metal−support interface is characterized by a short Pt−O distance, irrespective of the presence of chemisorbed hydrogen. An apparent L3 edge shift of 0.8 eV relative to bulk Pt is observed for the hydrogen-covered clusters. This shift is attributed to a decrease in the Pt L3 edge resonance (white line) intensity, as no corresponding shift is observed at the L2 edge. A hydrogen-related L2,3 XANES feature at 9 eV appears with nearly equal intensity at each edge. This peak is assigned to electronic transitions from Pt 2p levels to H 1s−Pt 5d antibonding states with mixed d3/2−d5/2 character. From the L2,3 XANES analysis, we find that the number of unoccupied d states in hydrogen-covered Pt clusters is 23% less than in bulk Pt. In contrast, the L2,3 XANES spectra of bare silica-supported Pt clusters are closely similar to those of bulk Pt; quantitative analysis reveals only a slight (4%) decrease in the number of unoccupied d states. DA - 1997/6/19/ PY - 1997/6/19/ DO - 10.1021/jp970244e VL - 101 IS - 25 SP - 4972-4977 SN - 1089-5647 ER - TY - JOUR TI - From micelles to randomly connected, bilayered membranes in dilute block copolymer blends AU - Laurer, JH AU - Fung, JC AU - Sedat, JW AU - Smith, SD AU - Samseth, J AU - Mortensen, K AU - Agard, DA AU - Spontak, RJ T2 - LANGMUIR AB - As macromolecular surfactants, diblock copolymers order into a variety of morphologies in the presence of a parent homopolymer. Here, we probe the effects of chemical incompatibility and interfacial rigidity on the morphology of copolymer/homopolymer blends at constant blend composition. Five copolymers, each possessing a random-sequence midblock that is varied from 0 to 40 wt % of the copolymer molecular weight, have been synthesized for this purpose. While copolymer micelles are representative of dilute (homopolymer-rich) blends, complex bilayered morphologies, including vesicles and the anomalous isotropic “sponge” phase, are produced upon increasing the midblock fraction. Small-angle neutron scattering provides a quantitative assessment of characteristic microstructural dimensions, while transmission electron microtomography yields the first three-dimensional images of the randomly connected, bilayered membrane comprising the sponge phase. DA - 1997/4/16/ PY - 1997/4/16/ DO - 10.1021/la9608876 VL - 13 IS - 8 SP - 2177-2180 SN - 0743-7463 ER - TY - JOUR TI - Effects of supporting electrolyte on the mass-transfer limited current for coupled chemical-electrochemical reactions AU - Hicks, MT AU - Fedkiw, PS T2 - JOURNAL OF ELECTROANALYTICAL CHEMISTRY AB - A Nernst diffusion-layer model is developed for the study of reactant diffusion-migration in electrolyte solutions with coupled chemical-electrochemical reactions. Specifically, proton reduction to hydrogen gas and the Kolbe oxidative dimerization of acetate to ethane and carbon dioxide are studied in an acetic acid solution with supporting electrolyte: an inert (LiClO4) and a reactive electrolyte (NaOH) are each considered. The model predicts concentration and potential profiles within the diffusion layer and the mass-transfer limited current density as a function of the ratio of the supporting-electrolyte concentration to that of acetic acid. For proton reduction, the ratio of the limiting to diffusion current increases with decreasing acid strength in the limit of zero supporting-electrolyte, while the opposite is true for the Kolbe oxidative dimerization of acetate. For the Kolbe oxidative dimerization of acetate in sodium hydroxide, a maximum exists in the ratio of the limiting to diffusion current when the concentration of sodium hydroxide is approximately equal to that of acetic acid. The maximum is a result of the weak-acid strong-base chemistry. Numerical calculations for proton reduction from acetic acid as a function of the supporting-electrolyte concentration are compared with published experimental data. The numerical results and experimental data are in agreement when there is an excess of supporting-electrolyte present, but diverge as the supporting-electrolyte concentration approaches zero. DA - 1997/3/15/ PY - 1997/3/15/ DO - 10.1016/S0022-0728(96)04932-7 VL - 424 IS - 1-2 SP - 75-92 SN - 0022-0728 KW - coupled chemical-electrochemical reactions KW - Nernst diffusion-layer model KW - proton reduction KW - Kolbe oxidative dimerization KW - supporting electrolyte effects ER - TY - JOUR TI - Effects of asphaltene solvency on stability of water-in-crude-oil emulsions AU - McLean, JD AU - Kilpatrick, PK T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - The formation of stable and persistent emulsions and foams in the production and refining of crude petroleum is a challenge which has defied broad and generic resolution for several decades. Rational and systematic approaches to demulsification have been slow to develop due to a lack of fundamental understanding of the molecular origins of emulsion stabilization and the full range of factors which govern emulsion stability. Several studies have shown the importance of resins and asphaltenes, which have the ability to organize and form rigid films at the oil/water interface. We have developed a molecular model in which we propose that the integrity of these films and thus their ability to stabilize water-in-crude-oil emulsions are sensitive to a variety of crude solvency parameters, such as aromaticity, resin-to-asphaltene ratio, and polar functional group concentration. This model was tested by correlating the stability of emulsions formed from a variety of crude oils—Arab Berri (Extra Light), Arab Heavy, Alaska North Slope, and San Joaquin Valley—in which the resin and asphaltene contents vary, as well as their specific characteristics. The results of the elemental and functional group characterization of these crudes and their fractions and the techniques utilized to obtain them were presented previously. Detailed quantitative protocols for gauging relative emulsion stability have been developed to further evaluate the proposed model by blending solvents of varying aromaticity and by doping isolated resins from different crudes into solvent-modified crudes. Dramatic destabilization of emulsions was accomplished by modifying the crude solvency in either fashion. Simple physical and chemical techniques for minimizing emulsion formation such as basic crude blending and solvent-recycle schemes will also be discussed. DA - 1997/5/15/ PY - 1997/5/15/ DO - 10.1006/jcis.1997.4807 VL - 189 IS - 2 SP - 242-253 SN - 0021-9797 ER - TY - JOUR TI - Effect of solvent conditions upon refolding pathways and intermediates for a simple lattice protein AU - Gupta, P AU - Hall, CK T2 - BIOPOLYMERS AB - Folding pathways and intermediates for a two-dimensional lattice protein have been investigated via computer simulation at various denaturant concentrations. The protein is represented as a chain of 8 hydrophobic (H) and 12 polar (P) beads on a square lattice sequenced in such a way that the native state is a compact hydrophobic core surrounded by a shell of polar beads. Two nonbonded H beads are said to attract each other with a potential of mean force of strength ϵ. Increasing |ϵ/kT| mimics decreasing the denaturant concentration in the solution. Dynamic Monte Carlo simulations have been performed in order to investigate the folding transition and the folding pathways. Sharp folding—unfolding transitions are observed and the folding process proceeds along well-defined pathways that are populated by partially folded intermediates. The folding pathways as well as the populations of the intermediates are strongly dependent upon the denaturant concentration. Generally, intermediates containing long open stretches of H beads are more populated at high denaturant concentration, whereas compact intermediates containing a substantial number of hydrophobic contacts are more populated at low denaturant concentrations. The folding process is also observed to be cooperative in nature in that the chain does not start folding until a key fold in the middle section of the chain is formed correctly. © 1997 John Wiley & Sons, Inc. Biopoly 42: 399–409, 1997 DA - 1997/10/5/ PY - 1997/10/5/ DO - 10.1002/(SICI)1097-0282(19971005)42:4<399::AID-BIP3>3.0.CO;2-L VL - 42 IS - 4 SP - 399-409 SN - 0006-3525 KW - protein folding KW - folding pathways KW - folding intermediates KW - computer simulation KW - solvent effects ER - TY - JOUR TI - Complex phase behavior of a disordered ''random'' diblock copolymer in the presence of a parent homopolymer AU - Laurer, JH AU - Ashraf, A AU - Smith, SD AU - Spontak, RJ T2 - LANGMUIR AB - Previous efforts addressing binary blends of a block copolymer and a parent homopolymer have principally employed ordered copolymers in either the intermediate- or strong-segregation regimes. In this work, blends composed of a disordered (75/25)-b-(50/50) poly[(styrene-r-isoprene)‘-b-(styrene-r-isoprene)‘‘] (S/I)‘-b-(S/I)‘‘ random diblock copolymer (RBC) and homopolystyrene (hS) have been investigated. Blend morphologies, characterized by transmission electron microscopy, are correlated with hS concentration and molecular weight, as well as with changes in the hS Tg, as measured by thermal calorimetry. At low hS fractions (up to 20 wt % hS), the S/I block sequences in the RBC induce competition between attractive and repulsive interactions with hS molecules, resulting in the formation of thin hS channel structures in a continuous RBC matrix. An increase in hS concentration or molecular weight serves to broaden the channels until the morphology resembles macrophase-separated hS domains containing micelle-like RBC dispersions. In blends with relatively high hS fractions (greater than 80 wt % hS), repulsive interactions between RBC and hS molecules are responsible for the formation of macroscopic RBC domains in a continuous hS matrix. These blend morphologies demonstrate that localized interactions between homopolymer molecules and each block of a copolymer exist, and can be probed, in the disordered state. DA - 1997/4/16/ PY - 1997/4/16/ DO - 10.1021/la960807y VL - 13 IS - 8 SP - 2250-2258 SN - 0743-7463 ER - TY - JOUR TI - Comparison of precipitation and extrography in the fractionation of crude oil residua AU - McLean, JD AU - Kilpatrick, PK T2 - ENERGY & FUELS AB - Four different crude oilsArab Heavy (AH), Arab Berri (AB), Alaskan North Slope (ANS), and San Joaquin Valley (SJV)were characterized by separating the crudes into compound classes by two different fractionation methodsextrography (ext) and asphaltene precipitation followed by extrographic isolation of the resins (ppt + ext). The fractions derived from these two methods of separation were characterized and compared in order to determine the most complete and discriminating compositional analysis for subsequent use in studies concerning the stability of emulsions or sludges which are produced by these crudes in refinery processing. The resin and asphaltene fractions are of primary interest due to their polar, surface-active nature, the central role these fractions play in stabilizing emulsions and sludges, and their resulting influence on crude processability. Preparatory-scale separations were developed and utilized to provide sufficient amounts of the polar fractions of these crudes for further studies. The H/C ratio and concentrations of S, N, and O as well as V and Ni contents were determined for each of the crudes and their respective fractions. The results of this investigation also provided useful information regarding the H-bonding capacity (as gauged by the functional group types and content) and aromaticity of the polar fractions of these particular crude oils. The polar functional groups and carbon types were identified and quantitated by FTIR and 13C NMR spectroscopy. FTIR analysis also provided an indirect measure of the polarity of substituent groups attached to the aromatic core of these molecules when comparing the results of the integration of the aromatic CC stretch with the aromaticity as measured by 13C NMR analysis. Both the H-bonding capacity and the aromaticity are considered to play a central role in determining the solubility of asphaltenes in the crude medium which in turn has a significant effect on the emulsifying potential of the crude oil. In the comparison of the two fractionation methods, the resin and total asphaltene yields were very similar for most of the crude types; however, the characteristics of these polar fractions varied considerably in all the crudes depending upon the method used to isolate them. There was strong evidence to support the prevailing sentiment that the fraction which is coined “asphaltenes” is greatly influenced and defined by the very method utilized to isolate this fraction. When considering and analyzing the characteristics of the polar materials in their totality (i.e., resins + asphaltenes), these materials were very similar in nature regardless of the fractionation method used to isolate them. However, irreversible adsorption of asphaltenic components (up to ∼0.8 wt % of whole crude) on the silica gel does occur when employing the extrographic technique. Thus, the ppt + ext fractionation method appears to be the simplest and most robust method to provide further understanding of the mechanisms which govern the stability of emulsions produced from different crude types. DA - 1997/// PY - 1997/// DO - 10.1021/ef9601125 VL - 11 IS - 3 SP - 570-585 SN - 0887-0624 ER - TY - JOUR TI - The influence of carboxymethylated chitosan on the structure, rheology, and dewatering properties of clay AU - Joyce, M. K. AU - Gilbert, R. D. AU - Khan, S. A. T2 - TAPPI Journal DA - 1997/// PY - 1997/// VL - 80 IS - 5 SP - 185-190 ER - TY - JOUR TI - Real-time FTIR and in situ rheological studies on the UV curing kinetics of thiol-ene polymers AU - Chiou, BS AU - Khan, SA T2 - MACROMOLECULES AB - Real-time FTIR spectroscopy and in situ dynamic rheology were used to characterize the UV curing kinetics of a thiol-ene system containing trimethylolpropane tris(2-mercaptoacetate) and trimethylolpropane diallyl ether. The combination of these two techniques offered a powerful approach for monitoring changes in the chemical and rheological properties of the system during UV curing. Comparable gel times were independently obtained from both FTIR spectroscopy and rheology, thereby validating the comparison of data obtained from each method. The thiol conversion determined from FTIR spectroscopy was correlated with the elastic modulus obtained from rheology. The conversion increased very rapidly during the initial stages of UV curing. However, the elastic modulus did not have an appreciable value until after 65% of the thiol functional groups have reacted, following which the elastic modulus increased at a rapid rate. From the Flory−Stockmayer theory of gelation, the critical thiol conversion at the gel point was determined to be 0.71. This indicated that the elastic modulus had an appreciable value only when the sample is close to its gel point, consistent with the step growth kinetics of the polymerization reaction. From the conversion data, the photoinitiated thiol-ene reaction was determined to be a second-order reaction. This second-order behavior was inconsistent with the termination mechanisms currently found in literature. A possible reason for such a discrepancy is discussed. DA - 1997/11/17/ PY - 1997/11/17/ DO - 10.1021/ma9708656 VL - 30 IS - 23 SP - 7322-7328 SN - 0024-9297 ER - TY - JOUR TI - Nitric oxide reduction using iridium electrodes on yttria-stabilized zirconia AU - Walsh, KJ AU - Fedkiw, PS T2 - SOLID STATE IONICS DA - 1997/12// PY - 1997/12// DO - 10.1016/S0167-2738(97)00402-5 VL - 104 IS - 1-2 SP - 97-108 SN - 0167-2738 KW - iridium electrode KW - nitrogen oxides KW - stabilized zirconia KW - electrochemical reduction ER - TY - JOUR TI - Molecular dynamics for polymeric fluids using discontinuous potentials AU - Smith, SW AU - Hall, CK AU - Freeman, BD T2 - JOURNAL OF COMPUTATIONAL PHYSICS AB - Molecular dynamics simulation techniques for systems interacting with discontinuous potentials are discussed. Optimization and efficiency techniques are summarized for performing discontinuous molecular dynamics on serial computers with direct application to polymer-like fluids. Comparisons are presented for two algorithms: (1) single-event scheduling, and (2) multiple-event scheduling. The single-event scheduling algorithm is approximately 75% faster than the multiple-event scheduling algorithm for molecular fluids but yields equivalent performance for atomic fluids. For the single-event scheduling method, a combination of link lists and neighbor lists are used when searching for possible particle interactions. The combination of efficiency techniques permits multibillion time step simulations for relatively large systems on desktop workstations. Both discontinuous molecular dynamics codes for single and multiple-event scheduling algorithms are available on the Internet. The utility of the method is demonstrated for entangled chains, tethered chains, and heteronuclear chain mixtures. DA - 1997/6// PY - 1997/6// DO - 10.1006/jcph.1996.5510 VL - 134 IS - 1 SP - 16-30 SN - 0021-9991 ER - TY - JOUR TI - Investigation of substrate dependent nucleation of plasma-deposited microcrystalline silicon on glass and silicon substrates using atomic force microscopy AU - Smith, LL AU - Srinivasan, E AU - Parsons, GN T2 - JOURNAL OF APPLIED PHYSICS AB - In order to define mechanisms for pulsed-gas plasma enhanced substrate-selective deposition of silicon, the initial stages of microcrystalline silicon (μc-Si) growth by plasma enhanced chemical vapor deposition on both c-Si and glass substrates were investigated by means of atomic force microscopy (AFM) and reflective high energy electron diffraction (RHEED). Differences in initial substrate morphology were reflected in significant differences in film surface morphology in the early stages of growth. AFM images and rms roughness measurements indicated that the initial growth on the c-Si substrate was three dimensional in character. On glass, the initial Si deposits were much more irregular in shape and the tallest features extended over wider areas than the initial deposits on c-Si. The character of the initial growth on glass was partly obscured by the roughness of the substrate, but the appearance of the initial Si deposits suggested a flatter and more two-dimensional character on glass than on c-Si. As the Si deposition progressed, the films on the different substrates developed similar morphology with increasing thickness. On the c-Si substrate, surface coverage was nearly complete at 50 Å. RHEED analysis of the films grown on c-Si revealed the presence of amorphous structure in the early stages of film growth, which began to transition to a randomly oriented μc-Si structure after 40–50 Å of growth. Observed differences in nucleation affirm and clarify proposed mechanisms and limitations for plasma enhanced selective μc-Si deposition. DA - 1997/12/15/ PY - 1997/12/15/ DO - 10.1063/1.366471 VL - 82 IS - 12 SP - 6041-6046 SN - 0021-8979 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000071043400022&KeyUID=WOS:000071043400022 ER - TY - JOUR TI - Hydrogen elimination and phase transitions in pulsed-gas plasma deposition of amorphous and microcrystalline silicon AU - Srinivasan, E AU - Parsons, GN T2 - JOURNAL OF APPLIED PHYSICS AB - Removal of hydrogen from the growth surface during silane plasma deposition of silicon is correlated with the transition from amorphous to microcrystalline film structure. Plasma deposition experiments were performed using a pulsed gas technique, where repeated steps of thin amorphous silicon film deposition, and atomic hydrogen (or deuterium) exposure are used to form microcrystalline and polycrystalline thin films at substrate temperatures below 250 °C. Infrared absorption and Raman spectroscopy are used to estimate the silicon-hydrogen bonding concentrations, and characterize crystal structure, respectively. Hydrogen elimination probed using real-time differentially pumped mass spectroscopy demonstrates that during atomic deuterium exposure, hydrogen abstraction by deuterium, rather than silicon etching, is the primary mechanism for hydrogen removal from the depositing surface. Polycrystalline material, with no shoulder at 480 cm−1 in the Raman spectrum, and grain sizes greater than 1000 Å, as determined by transmission electron microscopy, have been formed at temperatures below 250 °C. The amorphous to crystal transition is observed at substrate temperatures as low as 25 °C, with longer hydrogen exposure required at lower temperatures. Hydrogen is shown to be preferentially abstracted from monohydride (Si–H) units as compared to dihydride (SiH2) units at or near the depositing growth surface, consistent with ab initio energy calculations of hydrogen interactions with silicon hydrides. A transition in hydrogen removal kinetics is observed upon film crystallization, where the rate of hydrogen removal is reduced for more crystalline materials. These results are valuable for understanding surface reactions in low temperature crystalline silicon deposition, for example, for fabrication of high mobility thin film transistor structures on glass. DA - 1997/3/15/ PY - 1997/3/15/ DO - 10.1063/1.364309 VL - 81 IS - 6 SP - 2847-2855 SN - 0021-8979 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1997WP16700065&KeyUID=WOS:A1997WP16700065 ER - TY - JOUR TI - Evolution of VIMS at North Carolina State University AU - Balik, C. M. AU - Spontak, Robert J. AU - Weitzel, J. T2 - Journal of Materials Education DA - 1997/// PY - 1997/// VL - 19 IS - 1-2 SP - 59 ER - TY - JOUR TI - Equilibrium thermodynamics of homopolymers and clusters: Molecular dynamics and Monte Carlo simulations of systems with square-well interactions AU - Zhou, YQ AU - Karplus, M AU - Wichert, JM AU - Hall, CK T2 - JOURNAL OF CHEMICAL PHYSICS AB - The thermodynamics of homopolymers and clusters with square-well interactions of up to 64 particles are studied with constant-temperature discontinuous molecular dynamics (DMD) simulations; for comparison Monte Carlo (MC) simulations are also reported. Homopolymers composed of more than five beads are found to exhibit two or more equilibrium transitions. In the long chain limit, these multiple transitions correspond to gas-to-liquid, liquid-to-solid, and solid-to-solid transitions. In particular, the liquid-to-solid-like disorder-to-order transition for isolated 32mers and 64mers is strongly first order (bimodal energy distribution) at the reduced square-well diameter λ=1.5. As λ decreases from 1.5 to 1.3, the bimodal distribution becomes unimodal. The use of Lindemann’s rule for solids indicates that the structure formed right below the liquid-to-solid transition temperature has a solid core but a liquid surface. Comparing the homopolymer results with those for square-well clusters indicates that the bonding constraint in homopolymers increases the temperatures of transitions but decreases their strength. The solid structure of an isolated 64mer is nearly identical to that of a cluster of 64 beads. Possible approaches to the experimental observation of the solid-state for an isolated chain are discussed. DA - 1997/12/22/ PY - 1997/12/22/ DO - 10.1063/1.474186 VL - 107 IS - 24 SP - 10691-10708 SN - 0021-9606 ER - TY - JOUR TI - Chemical potential gradient driven permeation of small molecules through polymeric media AU - Sunderrajan, Suresh AU - Hall, Carol K. AU - Freeman, Benny D. T2 - The Journal of Chemical Physics AB - Grand canonical molecular dynamics techniques are used to study small molecular penetrant permeation through polymeric media. Penetrants are modeled as hard spheres and square-well spheres. The polymer is modeled as a collection of hard chains and square-well chains. Glassy polymers are modeled using stationary chains while rubbery polymers are modeled using mobile chains. Facilitated transport polymers are also modeled by varying the square-well depth for specific sites along polymer chains. Penetrant partitioning, mutual diffusivity, solubility, and permeability (taken to be a product of diffusivity and solubility) are calculated as a function of reservoir chemical potential, barrier mobility, and, for the facilitating polymer case, the strength of the penetrant/facilitating site attraction. Penetrant diffusivity, solubility, and hence permeability are greater in a mobile barrier than in a stationary barrier. Diffusivity decreases and solubility increases upon the addition of facilitating sites to the barrier or upon increasing the strength of the penetrant/facilitating site attraction. Permeability decreases in these cases, contradicting our expectations concerning the phenomenon of facilitated transport. Comparisons are made between the permeation results presented here and experimental facilitated transport systems. DA - 1997/12/22/ PY - 1997/12/22/ DO - 10.1063/1.475221 VL - 107 IS - 24 SP - 10714-10722 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.475221 DB - Crossref ER - TY - JOUR TI - Alcohol synthesis in a high-temperature slurry reactor AU - Roberts, GW AU - Marquez, MA AU - McCutchen, MS T2 - CATALYSIS TODAY AB - Abstract A family of hydrocarbon liquids has been discovered that is stable at temperatures up to about 400°C in the presence of synthesis gas. The performance of a commercial, ‘zinc chromite’, ‘high pressure’ methanol synthesis catalyst was evaluated in a slurry reactor using two of these liquids, decahydronaphthalene and tetrahydronaphthalene, to suspend the catalyst. The evaluation covered a range of temperatures from 275° to 425°C, total pressures from 6.9 to 17.2 MPa, H2/CO ratios from 0.5 to 2.0 and space velocities from 1500 to 10 000 sl kg(catalyst)−1 h−1. Methanol was the only significant product at the lower end of this temperature range. The methanol synthesis reaction was close to equilibrium at the highest temperature, and there were significant quantities of dimethyl ether, olefins, methane and carbon dioxide in the product. Catalyst performance was sensitive to the composition of the slurry liquid, but was relatively stable in decahydronaphthalene over a long period of time. DA - 1997/6/6/ PY - 1997/6/6/ DO - 10.1016/S0920-5861(96)00243-X VL - 36 IS - 3 SP - 255-263 SN - 0920-5861 KW - decahydronaphthalene KW - methanol KW - slurry reactor KW - tetrahydronaphthalene KW - zinc chromite ER - TY - JOUR TI - Simple photocatalysis model for photoefficiency enhancement via controlled, periodic illumination AU - Upadhya, S AU - Ollis, DF T2 - JOURNAL OF PHYSICAL CHEMISTRY B AB - Under steady illumination, aqueous phase photocatalytic oxidation reactions using titanium dioxide characteristically exhibit low quantum yields, i.e., the incident light is used inefficiently in the process. Sczechowski, Koval, and Noble1 reported substantially higher photoefficiencies (defined as reaction rate divided by incident photon rate) for TiO2 while using controlled, periodic illumination instead of continuous illumination in a flow system. We propose a transient kinetic model which suggests that rapid consumption of preadsorbed reactant inventory by photoproduced holes (or by their oxidation product, OH radical, etc.) accounts for such high photoefficiencies with periodic illumination and that the characteristically slow adsorption of additional oxygen and/or electron transfer to oxygen is responsible for low quantum yields observed under steady illumination. A model simulation provides trends of photoefficiency with variation of the length of light and dark periods which resemble the observed photoefficiency trends, but fundamental comparisons await photoefficiency and individual rate constant measurements on the same photocatalysts. DA - 1997/4/3/ PY - 1997/4/3/ DO - 10.1021/jp962649p VL - 101 IS - 14 SP - 2625-2631 SN - 1520-6106 ER - TY - JOUR TI - Purification and characterization of two functional forms of intracellular protease PFPI from the hyperthermophilic Archaeon Pyrococcus furiosus AU - Halio, S. B. AU - Bauer, M. W. AU - Mukund, S. AU - Adams, M. W. W. AU - Kelly, R. M. T2 - Applied and Environmental Microbiology DA - 1997/// PY - 1997/// VL - 63 IS - 1 SP - 289-295 ER - TY - JOUR TI - Purification and characterization of extremely thermostable beta mannanase, beta mannosidase, and alpha galactosidase from the hyperthermophilic eubacterium Thermotoga neapolitana AU - Duffaud, G. D. AU - McCutchen, C. M. AU - Leduc, P. AU - Parker, K. N. AU - Kelly, R. M. T2 - Applied and Environmental Microbiology DA - 1997/// PY - 1997/// VL - 63 IS - 1 SP - 169-177 ER - TY - JOUR TI - Pressure-dependent photon correlation spectroscopic investigation of poly(propylene oxide) near the glass transition AU - Smith, SW AU - Freeman, BD AU - Hall, CK T2 - MACROMOLECULES AB - The effect of pressure on structural relaxations in poly(propylene oxide) (PPO; MW = 4000) near the glass transition has been determined using photon correlation spectroscopy. Experimental results are reported for pressures ranging from 2.5 to 3.9 kbar at 253 K. The structural relaxation exhibits two distinct processes separated by ∼3 orders of magnitude in time. This observation is consistent with results of dielectric relaxation studies of PPO. The faster relaxation is associated with local segmental motions important in the glass−rubber transition. The mean relaxation time for the faster process exhibits an exponential dependence on pressure. DA - 1997/4/7/ PY - 1997/4/7/ DO - 10.1021/ma960408+ VL - 30 IS - 7 SP - 2052-2057 SN - 0024-9297 ER - TY - JOUR TI - Macromolecular dynamics in extensional flows .1. Birefringence and viscometry AU - Carrington, SP AU - Tatham, JP AU - Odell, JA AU - Saez, AE T2 - POLYMER AB - The opposed jets apparatus is used to investigate the dynamics of the coil-stretch transition of polymer solutions in an idealized stagnation point extensional flow-field. A linear CCD detector allows optical retardation profiles to be recorded as the strain rate is varied. A numerical transformation enables true birefringence profiles to be produced, which enable the assessment of localized molecular orientation and stretching around the stagnation point. High molecular weight, closely monodisperse aPS and PEO are studied in θ and good solvents. Flow modification effects are apparent to extremely low concentration (≈c∗/100). Under θ conditions, the width of the transition is consistent with the residual polydispersity. Simultaneous measurements of flow resistance enable the determination of the effective extensional viscosity. The increase in extensional viscosity due to molecular stretching is found to be of the order of the number of equivalent flexible units in the chain, after correction is made for the area of high molecular extension. DA - 1997/8// PY - 1997/8// DO - 10.1016/S0032-3861(96)00999-8 VL - 38 IS - 16 SP - 4151-4164 SN - 0032-3861 KW - birefringence KW - viscometry KW - extensional flow ER - TY - JOUR TI - Heterogeneous photocatalysis for purification, decontamination and deodorization of air AU - Peral, J AU - Domenech, X AU - Ollis, DF T2 - JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY AB - A research review of gas–solid heterogeneous photocatalysis is presented, ranging from details of pioneering works, which dealt with basic phenomena like oxygen and water vapor adsorption, to recent applications to pollutant removal in contaminated atmospheres. Special interest is taken in describing the different reactor configurations studied so far in this emerging and promising field. © 1997 SCI DA - 1997/10// PY - 1997/10// DO - 10.1002/(SICI)1097-4660(199710)70:2<117::AID-JCTB746>3.0.CO;2-F VL - 70 IS - 2 SP - 117-140 SN - 0268-2575 KW - photocatalysis KW - photoreactor KW - gas-phase KW - pollution control KW - air purification ER - TY - JOUR TI - Dominant monohydride bonding in hydrogenated amorphous silicon thin films formed by plasma enhanced chemical vapor deposition at room temperature AU - Srinivasan, E AU - Lloyd, DA AU - Parsons, GN T2 - JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS AB - Hydrogenated amorphous silicon (a-Si:H) prepared by plasma enhanced chemical vapor deposition (PECVD) with silane, typically shows significant dihydride bonding and high defect density when the substrate temperature is less than 200 °C. Monohydride bonding is associated with low defect densities, and is usually observed only above 250 °C. Using rf (13.56 MHz) PECVD, we have deposited a-Si:H films at a substrate temperature of 35 °C using silane diluted with helium, and found that films with dominant monohydride bonding can be deposited without significant substrate heating. A specific ion enhanced reaction mechanism that is consistent with the results is proposed. As deposited, the films with predominant monohydride bonding show low dark conductivity (10−9 S/cm) and low photoconductivity (10−7 S/cm under 100 mW/cm2 while light illumination). Annealing the films for 3–4 h at 150 °C, resulted in an improved photoconductivity with photo to dark conductivity ratio near 105. These films may be valuable for the fabrication of thin film electronics on novel substrates compatible with only low temperature processes. DA - 1997/// PY - 1997/// DO - 10.1116/1.580480 VL - 15 IS - 1 SP - 77-84 SN - 0734-2101 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1997WD69000015&KeyUID=WOS:A1997WD69000015 ER - TY - JOUR TI - Compositionally symmetric diblock copolymer blends of moderate polydispersity AU - Kane, L. AU - Satkowski, M. M. AU - Smith, S. D. AU - Spontak, Richard T2 - Journal of Polymer Science. Part B, Polymer Physics AB - Recent experimental evidence and theoretical predictions indicate that binary blends of relatively monodisperse diblock copolymers remain miscible if the molecular weight disparity of the constituent copolymers is not too great. In this work, we examine the effect of moderate copolymer polydispersity on both the microstructural characteristics and phase behavior of blends prepared from four compositionally symmetric poly(styrene-b-isoprene) (SI) diblock copolymers ranging in polydispersity (M̄w/M̄n) from 1.02 to 1.30. Blend periodicities, measured by small-angle X-ray scattering, compare favorably with predictions from a strong segregation theory proposed for lamellar diblock copolymer blends composed of monomolecular copolymers. Transmission electron microscopy, employed to ascertain the real-space morphological characteristics of these blends, reveals that a lamellar → cylindrical transition occurs in macrophase-separated blends. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2653–2658, 1997 DA - 1997/// PY - 1997/// DO - 10.1002/(sici)1099-0488(19971130)35:16<2653::aid-polb8>3.3.co;2-d VL - 35 IS - 16 SP - 2653–2658 ER - TY - JOUR TI - Shear-thickening response of fumed silica suspensions under steady and oscillatory shear AU - Raghavan, , SR AU - Khan, SA T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - Suspensions of fumed silica in polypropylene glycol exhibit shear-thickening under steady shear and "strain-thickening" under oscillatory shear. Strain-thickening refers to a sharp increase in the complex viscosity eta* observed at critical combinations of strain-amplitude and frequency. Two regimes of strain-thickening behavior have been found: The first occurs at high critical strains and low frequencies, whereas the second occurs at high critical frequencies and a constant lower strain. Strain-thickening in the first regime can be explicitly correlated with steady shear-thickening, using a modified version of the Cox-Merz rule. Accordingly, strain-thickening data for the complex viscosity eta* as a function of the maximum dynamic shear-rate gamma0omega can be superposed against shear-thickening data for the steady viscosity as a function of the steady shear rate. Such a correlation between the two kinds of thickening phenomena has not been reported previously. The combination of shear- and strain-thickening behavior can be qualitatively explained using a clustering mechanism, which attributes the various phenomena to the formation of temporary, flow-induced clusters. The two regimes of strain-thickening are a result of differences in the relative ease of cluster formation. DA - 1997/1/1/ PY - 1997/1/1/ DO - 10.1006/jcis.1996.4581 VL - 185 IS - 1 SP - 57-67 SN - 0021-9797 KW - shear-thickening KW - strain-thickening KW - suspensions KW - rheology KW - fumed silica ER - TY - JOUR TI - Microstructural analysis of a cubic bicontinuous morphology in a neat SIS triblock copolymer AU - Laurer, JH AU - Hajduk, DA AU - Fung, JC AU - Sedat, JW AU - Smith, SD AU - Gruner, SM AU - Agard, DA AU - Spontak, RJ T2 - MACROMOLECULES AB - ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTMicrostructural Analysis of a Cubic Bicontinuous Morphology in a Neat SIS Triblock CopolymerJonathan H. Laurer, Damian A. Hajduk, Jennifer C. Fung, John W. Sedat, Steven D. Smith, Sol M. Gruner, David A. Agard, and Richard J. SpontakView Author Information Department of Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695, Department of Physics, Princeton University, Princeton, New Jersey 08544, Graduate Group in Biophysics, University of California, San Francisco, California 94143, Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143, Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239, and Howard Hughes Medical Institute, University of California, San Francisco, California 94143 Cite this: Macromolecules 1997, 30, 13, 3938–3941Publication Date (Web):June 30, 1997Publication History Received1 April 1997Published online30 June 1997Published inissue 1 June 1997https://doi.org/10.1021/ma970449lCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views631Altmetric-Citations88LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (202 KB) Get e-AlertsSUBJECTS:Copolymers,Morphology,Order,Scattering,X-ray scattering Get e-Alerts DA - 1997/6/30/ PY - 1997/6/30/ DO - 10.1021/ma970449l VL - 30 IS - 13 SP - 3938-3941 SN - 0024-9297 ER - TY - JOUR TI - Long-term permeation properties of poly(1-trimethylsilyl-1-propyne) membranes in hydrocarbon-vapor environment AU - Pinnau, I AU - Casillas, CG AU - Morisato, A AU - Freeman, BD T2 - JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS AB - Poly(1-trimethylsilyl-1-propyne) (PTMSP), a high free-volume glassy di-substituted polyacetylene, has the highest gas permeabilities of all known polymers. The high gas permeabilities in PTMSP result from its very high excess free volume and connectivity of free volume elements. Permeability coefficients of permanent gases in PTMSP decrease dramatically over time due to loss of excess free volume. The effects of aging on gas permeability and selectivity of PTMSP membranes continuously exposed to a 2 mol % n-butane/98 mol % hydrogen mixture over a period of 47 days are reported. The permeation properties of PTMSP membranes are quite stable when the polymer is continuously exposed to a gas mixture containing a highly sorbing organic vapor such af n-butane. The n-butane/hydrogen selectivity was essentially constant for the 47-day test period at a value of 29, or 88% of the initial value of the as-cast film of 33. Condensable gases such as n-butane may serve as a “filler” in the nonequilibrium free volume of the polymer, thereby preserving the high level of excess free volume. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1483–1490, 1997 DA - 1997/7/30/ PY - 1997/7/30/ DO - 10.1002/(SICI)1099-0488(19970730)35:10<1483::AID-POLB2>3.0.CO;2-T VL - 35 IS - 10 SP - 1483-1490 SN - 0887-6266 KW - poly(1-trimethylsilyl-1-propyne) KW - physical aging KW - hydrocarbon vapors KW - mixed gas permeation ER - TY - JOUR TI - Identification of benzene oxide as a product of benzene metabolism by mouse, rat, and human liver microsomes AU - Lovern, MR AU - Turner, MJ AU - Meyer, M AU - Kedderis, GL AU - Bechtold, WE AU - Schlosser, PM T2 - CARCINOGENESIS AB - Benzene is a ubiquitous environmental pollutant that is known to cause hematotoxicity and leukemia in humans. The initial oxidative metabolite of benzene has long been suspected to be benzene oxide (3,5-cyclohexadiene-1,2-oxide). During in vitro experiments designed to characterize the oxidative metabolism of [14C]benzene, a metabolite was detected by HPLC-radioactivity analysis that did not elute with other known oxidative metabolites. The purpose of our investigation was to prove the hypothesis that this metabolite was benzene oxide. Benzene (1 mM) was incubated with liver microsomes from human donors, male B6C3F1 mice, or male Fischer-344 rats, NADH (1 mM), and NADPH (1 mM) in 0.1 M sodium phosphate buffer (pH 7.4) and then extracted with methylene chloride. Gas chromatography-mass spectrometry analysis of incubation extracts for mice, rats, and humans detected a metabolite whose elution time and mass spectrum matched that of synthetic benzene oxide. The elution time of the benzene oxide peak was approximately 4.1 min, while phenol eluted at approximately 8 min. Benzene oxide also coeluted with the HPLC peak of the previously unidentified metabolite. Based on the 14C activity of this peak, the concentration of benzene oxide was determined to be approximately 18 microM, or 7% of total benzene metabolites, after 18 min of incubation of mouse microsomes with 1 mM benzene. The metabolite was not observed in incubations using heat-inactivated microsomes. This is the first demonstration that benzene oxide is a product of hepatic benzene metabolism in vitro. The level of benzene oxide detected suggests that benzene oxide is sufficiently stable to reach significant levels in the blood of mice, rats, and humans and may be translocated to the bone marrow. Therefore benzene oxide should not be excluded as a possible metabolite involved in benzene-induced leukemogenesis. DA - 1997/9// PY - 1997/9// DO - 10.1093/carcin/18.9.1695 VL - 18 IS - 9 SP - 1695-1700 SN - 0143-3334 ER - TY - JOUR TI - Preparing the professoriate: a study in mentorship AU - Beaudoin, S. P. AU - Felder, R. M. T2 - Journal of Graduate Teaching Assistant Development DA - 1997/// PY - 1997/// VL - 4 IS - 3 SP - 87-91 ER - TY - JOUR TI - It takes one to know one AU - Brent, R. AU - Felder, R. M. T2 - CEE, Chemical Engineering Education DA - 1997/// PY - 1997/// VL - 31 IS - 1 SP - 32-33 ER - TY - JOUR TI - Phase behaviour of aqueous hydroxypropylcellulose mesophase mixtures: Molecular weight considerations AU - Wang, BC AU - Spontak, RJ T2 - LIQUID CRYSTALS AB - As a self-organizing macromolecule, hydroxypropylcellulose serves as an excellent candidate for studies of complex polymer mixtures. In this work, we examine aqueous mixtures composed of two hydroxypropylcellulose grades, Klucel-F (HPC) and Klucel-H (HHPC), with molecular weights of 10 5 and 10 6 g mol - 1, respectively. Polarized light microscopy and deuterium nuclear magnetic resonance have been utilized to ascertain changes in the chiral nematic mesophase of HPC upon addition of 15 wt% HHPC. Results obtained here suggest that the HHPC either disrupts the molecular organization of the HPC mesophase, or induces immiscibility and partitions between HPC- and HHPC-rich phases. DA - 1997/3// PY - 1997/3// DO - 10.1080/026782997209432 VL - 22 IS - 3 SP - 359-365 SN - 0267-8292 ER - TY - JOUR TI - Trichloroethylene-promoted photocatalytic oxidation of air contaminants AU - dHennezel, O AU - Ollis, DF T2 - JOURNAL OF CATALYSIS AB - The prospects for photocatalytic purification and treatment of air depend centrally on finding conditions for which the apparent photoefficiency for contaminant disappearance is near or above 100%. We recently demonstrated that destruction of a low photoefficiency contaminant, toluene, by addition of a high photoefficiency compound, trichloroethylene, could raise the toluene photoefficiency to provide 100% conversion in a single pass, fixed bed illuminated catalyst, using a residence time of about 5–6 ms. The present paper establishes the generality of this TCE enhancement of contaminant rate and photoefficiency by examining the photocatalytic oxidation of various common contaminants at 50 mg/m3in air, including alcohols, aldehydes, ketones, aromatics, and chloroalkanes using near-UV-illuminated titanium dioxide powder in a flow reactor, in the absence and presence of trichloroethylene (TCE). Compounds exhibiting TCE rate promotion were toluene, ethylbenzene,m-xylene, methyl ethyl ketone (MEK), acetaldehyde, butyraldehyde, methyltert-butyl ether (MTBE), methyl acrylate, 1,4-dioxane, and hexane. Rate inhibition by TCE was exhibited for acetone, methylene chloride, chloroform, and 1,1,1-trichloroethane. TCE presence had almost no effect on the benzene and methanol rates. Butanol and vinyl acetate single component conversions were 100% under our standard low flow rate conditions; increasing the flow rate quenched TCE conversion in the presence of butanol, and therefore no TCE enhancement effect could be noted. DA - 1997/4/1/ PY - 1997/4/1/ DO - 10.1006/jcat.1997.1552 VL - 167 IS - 1 SP - 118-126 SN - 0021-9517 ER - TY - JOUR TI - Removal of oil films from stainless steel tubes AU - Yan, JF AU - Saez, AE AU - Grant, CS T2 - AICHE JOURNAL AB - Abstract The removal of oil films from the inner surface of a stainless steel tube cell using aqueous cleaning solutions was studied. The two oils used in the cleaning experiments, Sunquench 1042 and heavy mineral oil, contained P 32 labeled tributyl phosphate (TBP) as a radioactive tracer. The β ‐ particles emitted from the radioactive TBP were detected by a CaF 2 scintillator and used as a measure of the amount of oil remaining in the tube cell. Cleaning experiments performed at different flow rates, surface treatment, and surfactant concentrations indicated that initially the oil films were removed rapidly. At the end of the experiments, the oil removal rate reduced significantly, eventually becoming negligible. The stainless steel morphology affected oil removal significantly, and the rougher tube tended to retard the oil removal. The rate and extent of the decontamination were significantly increased in the presence of sodium dodecyl sulfate, a nonionic surfactant. Experimental data were compared to a hydrodynamic model based on the removal of a liquid contaminant from a solid surface by an immiscible fluid. The model deviated from the experimental data due to the presence of instabilities at the oil‐water interface. DA - 1997/1// PY - 1997/1// DO - 10.1002/aic.690430127 VL - 43 IS - 1 SP - 251-259 SN - 0001-1541 ER - TY - PAT TI - Method of reducing the viscosity of a black liquor AU - Spontak, R. J. AU - Roberts, J. E. AU - Prevysh, V. A. AU - Khan, S. A. C2 - 1997/// DA - 1997/// PY - 1997/// ER - TY - JOUR TI - Effects of asphaltene aggregation in model heptane-toluene mixtures on stability of water-in-oil emulsions AU - McLean, JD AU - Kilpatrick, PK T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - As part of an ongoing investigation into the stability of water-in-crude oil emulsions, model oils have been utilized to further probe the effects of crude solvency as well as specific resin-asphaltene interactions on emulsion stability. These model oils were constructed by dissolving varying amounts of resins and/or asphaltenes in a mixture of heptane and toluene. The resins and asphaltenes used in this study were isolated from four different crude types-Arab Berri (AB), Arab Heavy (AH), Alaska North Slope (ANS), and San Joaquin Valley (SJV)-and characterized in a previous study using heptane precipitation of the asphaltenes followed by an extrographic separation of the resins from silica gel. Asphaltenes dissolved in heptol at concentrations of just 0.5% were shown to generate emulsions which were even more stable than those generated from their respective whole crude oils. Some types of resins (e.g., from AH and SJV) also demonstrated an ability to stabilize emulsions although these resin-stabilized emulsions were considerably less stable than those prepared with asphaltenes. The primary factors governing the stability of these model emulsions were the aromaticity of the crude medium (as controlled by the heptane:toluene ratio), the concentration of asphaltenes, and the availability of solvating resins in the oil (i.e., the resin/asphaltene or R/A ratio). The model emulsions were the most stable when the crude medium was 30-40% toluene and in many cases at small R/A ratios (i.e., R/A