TY - CONF TI - Electrochemistry: Synthesis and Destruction: Proceedings of the U.S. Army Research Office Workshop A2 - Fedkiw, P. C2 - 1996/// DA - 1996/// PB - U.S. Army Research Office ER - TY - CONF TI - Disposable Fuel Cells: Proceedings of the U.S. Army Research Office Workshop A2 - Fedkiw, P. A2 - Smyth, W. C2 - 1996/// DA - 1996/// PB - U.S. Army Research Office ER - TY - CONF TI - A Model of Mass-Transport Limited Copper Electrodeposition from Cyanide Electrolyte AU - Fedkiw, P. AU - Dudek, D. T2 - American Electroplaters and Surface Finishers Society C2 - 1996/6// C3 - Proceedings of the AESF Annual Technical Conference / American Electroplaters and Surface Finishers Society DA - 1996/6// PY - 1996/6// VL - 83 ER - TY - CHAP TI - Inert gas dilution and ion bombardment effects in room temperature (35 degrees C) plasma deposition of a-Si:H AU - Srinivasan, E AU - Lloyd, DA AU - Fang, M AU - Parsons, GN AU - Hack, M AU - Schiff, EA AU - Wagner, S AU - Schropp, R AU - Matsuda, A T2 - Amorphous Silicon Technology - 1996 PY - 1996/// VL - 420 SP - 399-404 PB - SE - UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1996BH07P00064&KeyUID=WOS:A1996BH07P00064 ER - TY - JOUR TI - Dynamic rate and thickness metrology during poly-Si rapid thermal chemical vapor deposition from SiH4 using real time in situ mass spectrometry (vol 14, pg 267, 1996) AU - Tedder, LL AU - Rubloff, GW AU - Conaghan, BF AU - Parsons, GN T2 - Journal of Vacuum Science & Technology a-Vacuum Surfaces and Films AB - First Page DA - 1996/// PY - 1996/// DO - 10.1116/1.580187 VL - 14 IS - 4 SP - 2680 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1996VA96400112&KeyUID=WOS:A1996VA96400112 ER - TY - BOOK TI - Thermodynamics AU - Gubbins, Keith AU - Pitzer, Kenneth Sanborn DA - 1996/// PY - 1996/// ET - third PB - American Institute of Chemical Engineers ER - TY - JOUR TI - Confessions of a graduate student recruiter AU - Kelly, R.M. T2 - Chemical Engineering Education DA - 1996/// PY - 1996/// VL - 30 IS - 4 SP - 262–265 ER - TY - CONF TI - Graft polymerization and other methods to reduce the hygroscopic nature of cellulose insulation AU - Oommen, T.V. AU - Andrady, A.L. T2 - 1996 IEEE International Symposium on Electrical Insulation AB - Cellulosic insulation materials are widely used in power transformers and other high voltage devices, but require intensive drying out to remove all moisture. This paper describes three methods used to modify cellulose to reduce its hygroscopicity, of which graft polymerization was the most successful method. The modified paper sheets, however, lost some mechanical strength properties, and showed a tendency to be thicker than the starting material. C2 - 1996/// C3 - Conference Record of the 1996 IEEE International Symposium on Electrical Insulation CY - Montreal, Quebec, Canada DA - 1996/// PY - 1996/6/16/ DO - 10.1109/ELINSL.1996.549401 VL - 2 SP - 538–541 PB - IEEE SN - 0780335317 ER - TY - CHAP TI - Ultraviolet Radiation and Polymers AU - Andrady, Anthony L. T2 - Physical properties of polymers handbook A2 - Mark, J. PY - 1996/// SP - 547–557 PB - American Institute of Physics Press SN - 9781563962950 9781563965982 9781563965999 ER - TY - CHAP TI - Biodegradation of Polymers AU - Andrady, A.L. T2 - Physical properties of polymers handbook A2 - Mark, James E. T3 - AIP series in polymers and complex materials PY - 1996/// SP - 625–636 PB - American Institute of Physics Press SN - 9781563962950 9781563965982 9781563965999 ER - TY - JOUR TI - Wavelength sensitivity of enhanced photodegradable polyethylenes, ECO, and LDPE/MX AU - Andrady, A. L. AU - Pegram, J. E. AU - Searle, N. D. T2 - Journal of Applied Polymer Science AB - The wavelength sensitivity for decrease in percent elongation at break of ethylene carbon monoxide copolymer (ECO) and a low density polyethylene containing a metal compound prooxidant (LDPE/MX) on exposure to a borosilicate-filtered xenon-arc source was determined using a set of sharp cut-on filters. The spectral region primarily responsible for the degradation at 60°C is 323–328 nm for ECO and 323–338 nm for LDPE/MX. At 77°C, the sensitivity shifts about 10 nm to longer wavelengths. Based on the wavelength sensitivity of these materials to solar simulated radiation and the transmission properties of window glass, these materials can be expected to lose desirable mechanical properties when exposed to window-glass-filtered sunlight. © 1996 John Wiley & Sons, Inc. DA - 1996/11/28/ PY - 1996/11/28/ DO - 10.1002/(sici)1097-4628(19961128)62:9<1457::aid-app15>3.0.co;2-w VL - 62 IS - 9 SP - 1457-1463 J2 - J. Appl. Polym. Sci. LA - en OP - SN - 0021-8995 1097-4628 UR - http://dx.doi.org/10.1002/(sici)1097-4628(19961128)62:9<1457::aid-app15>3.0.co;2-w DB - Crossref ER - TY - JOUR TI - Spectral sensitivity of chitosan photodegradation AU - Andrady, Anthony L. AU - Torikai, Ayako AU - Kobatake, Takahiro T2 - Journal of Applied Polymer Science AB - The wavelength sensitivity of photodegradation of solvent-cast chitosan films exposed to monochromatic UV-visible radiation is reported. Measurements were made of changes in absorption spectra, both in the UV-visible region and in the infrared region, as well as changes in dilute solution viscosity of samples, on irradiation at selected wavelengths. Action spectra are reported for these processes. A mechanism of photodegradation based on changes in Fourier transform infrared (FTIR) spectra of irradiated chitosan is presented. © 1996 John Wiley & Sons, Inc. DA - 1996/11/28/ PY - 1996/11/28/ DO - 10.1002/(sici)1097-4628(19961128)62:9<1465::aid-app16>3.0.co;2-y VL - 62 IS - 9 SP - 1465-1471 J2 - J. Appl. Polym. Sci. LA - en OP - SN - 0021-8995 1097-4628 UR - http://dx.doi.org/10.1002/(sici)1097-4628(19961128)62:9<1465::aid-app16>3.0.co;2-y DB - Crossref ER - TY - JOUR TI - Molecular Estimates of the Moduli of Tough, Elastic Networks Formed Through End-linking of Poly(Dimethyl Siloxane Oligomers AU - Tonelli, A.E. AU - Andrady, A.L. T2 - Computational and Theoretical Polymer Science DA - 1996/// PY - 1996/// VL - 6 SP - 103–108 ER - TY - CHAP TI - Proteases and Glycosyl Hydrolases from Hyperthermophilic Microorganisms AU - Bauer, Michael W. AU - Halio, Sheryl B. AU - Kelly, Robert M. T2 - Advances in Protein Chemistry AB - This chapter discusses hydrolytic enzymes proteases and glycosyl hydrolases. Many heterotrophic hyperthermophilic micro-organisms (those able to grow above 90°C with an optimum above 80°C) isolated, utilize peptides and carbohydrates to fulfill their nutritional requirements. Assimilation of these substrates is initiated by an array of hydrolytic enzymes, particularly proteases and glycosyl hydrolases. A number of these hydrolases are isolated from several hyperthermophilic species and are characterized biochemically. These hydrolytic enzymes from hyperthermophiles involved in polypeptide and carbohydrate modifications are identified and characterized. These enzymes are thermostable and thermoactive, and in many cases, they have substrate specificities analogous to less thermostable counterparts from mesophilic organisms. Most proteases and glycosidases isolated from hyperthermophilic micro-organisms come from a very limited number of species of the archaeal genera Pyrococcus and Thermococcus and the eubacterial genus Thermotoga. The future study of these enzymes provides clues to the evolution of physiological functions, metabolic pathways, and protein structure. Cellular regulation pathways for many of these enzymes are not yet determined. PY - 1996/// DO - 10.1016/s0065-3233(08)60364-2 SP - 271-310 OP - PB - Elsevier SN - 9780120342488 UR - http://dx.doi.org/10.1016/s0065-3233(08)60364-2 DB - Crossref ER - TY - JOUR TI - Sequence, expression in Escherichia coli, and analysis of the gene encoding a novel intracellular protease (PfpI) from the hyperthermophilic archaeon Pyrococcus furiosus AU - Halio, S B AU - Blumentals, I I AU - Short, S A AU - Merrill, B M AU - Kelly, R M T2 - Journal of Bacteriology AB - A previously identified intracellular proteolytic activity in the hyperthermophilic archaeon Pyrococcus furiosus (I. I. Blumentals, A. S. Robinson, and R. M. Kelly, Appl. Environ. Microbiol. 56:1992-1998, 1990) was found to be a homomultimer consisting of 18.8-kDa subunits. Dissociation of this native P. furiosus protease I (PfpI) into a single subunit was seen by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) but only after trichloroacetic acid precipitation; heating to 95 degrees C in the presence of 2% SDS and 80 mM dithiothreitol did not dissociate the protein. The gene (pfpI) coding for this protease was located in genomic digests by Southern blotting with probes derived from the N-terminal amino acid sequence. pfpI was cloned, sequenced, and expressed in active form in Escherichia coli as a fusion protein with a histidine tag. The recombinant protease from E. coli showed maximum proteolytic activity at 95 degrees C, and its half-life was 19 min at this temperature. This level of stability was significantly below that previously reported for the enzyme purified by electroelution of a 66-kDa band from SDS-PAGE after extended incubation of cell extracts at 98 degrees C in 1% SDS (>30 h). The pfpI gene codes for a polypeptide of 166 amino acid residues lacking any conserved protease motifs; no protease activity was detected for the 18.8-kDa PfpI subunit (native or recombinant) by substrate gel assay. Although an immunological relationship of this protease to the eukaryotic proteasome has been seen previously, searches of the available databases identified only two similar amino acid sequences: an open reading frame of unknown function from Staphylococcus aureus NCTC 8325 (171 amino acid residues, 18.6 kDa, 41% identity) and an open reading frame also of unknown function in E. coli (172 amino acid residues, 18.8 kDa, 47% identity). Primer extension experiments with P. furiosus total RNA defined the 5' end of the transcript. There are only 10 nucleotides upstream of the start of translation; therefore, it is unlikely that there are any pre- or pro-regions associated with PfpI which could have been used for targeting or assembly of this protease. Although PfpI activity appears to be the dominant proteolytic activity in P. furiosus cell extracts, the physiological function of PfpI is unclear. DA - 1996/5// PY - 1996/5// DO - 10.1128/jb.178.9.2605-2612.1996 VL - 178 IS - 9 SP - 2605-2612 J2 - J Bacteriol LA - en OP - SN - 0021-9193 1098-5530 UR - http://dx.doi.org/10.1128/jb.178.9.2605-2612.1996 DB - Crossref ER - TY - JOUR TI - Growth Physiology of the Hyperthermophilic Archaeon Thermococcus litoralis: Development of a Sulfur-Free Defined Medium, Characterization of an Exopolysaccharide, and Evidence of Biofilm Formation AU - Rinker, K D AU - Kelly, R M T2 - Applied and Environmental Microbiology AB - Nutritional characteristics of the hyperthermophilic archaeon Thermococcus litoralis have been investigated with emphasis on the development of a sulfur-free, defined growth medium, analysis of an exocellular polysaccharide, and formation of a biofilm. An artificial-seawater-based medium, containing 16 amino acids, adenine, uracil, vitamins, and trace elements, allowed T. litoralis to attain growth rates and cell densities similar to those found with complex media. Four amino acids (alanine, asparagine, glutamine, and glutamate) were not included due to their lack of effect on growth rates and cell yields. In this medium, cultures reached densities of 10(sup8) cells per ml, with doubling times of 55 min (without maltose) or 43 min (with maltose). Neither the addition of elemental sulfur nor the presence of H(inf2) significantly affected cell growth. A sparingly soluble exopolysaccharide was produced by T. litoralis grown in either defined or complex media. Analysis of the acid-hydrolyzed exopolysaccharide yielded mannose as the only monosaccharidic constituent. This exopolysaccharide is apparently involved in the formation of a biofilm on polycarbonate filters and glass slides, which is inhabited by high levels of T. litoralis. Biofilm formation by hyperthermophilic microorganisms in geothermal environments has not been examined to any extent, but further work in this area may provide information related to the interactions among high-temperature organisms. DA - 1996/12// PY - 1996/12// DO - 10.1128/aem.62.12.4478-4485.1996 VL - 62 IS - 12 SP - 4478-4485 J2 - Appl Environ Microbiol LA - en OP - SN - 0099-2240 1098-5336 UR - http://dx.doi.org/10.1128/aem.62.12.4478-4485.1996 DB - Crossref ER - TY - JOUR TI - Comparison of a β-Glucosidase and a β-Mannosidase from the Hyperthermophilic Archaeon Pyrococcus furiosus AU - Bauer, Michael W. AU - Bylina, Edward J. AU - Swanson, Ronald V. AU - Kelly, Robert M. T2 - Journal of Biological Chemistry AB - Two distinct exo-acting, β-specific glycosyl hydrolases were purified to homogeneity from crude cell extracts of the hyperthermophilic archaeon Pyrococcus furiosus: a β-glucosidase, corresponding to the one previously purified by Kengen et al. (Kengen, S. W. M., Luesink, E. J., Stams, A. J. M., and Zehnder, A. J. B. (1993) Eur. J. Biochem. 213, 305-312), and a β-mannosidase. The β-mannosidase and β-glucosidase genes were isolated from a genomic library by expression screening. The nucleotide sequences predicted polypeptides with 510 and 472 amino acids corresponding to calculated molecular masses of 59.0 and 54.6 kDa for the β-mannosidase and the β-glucosidase, respectively. The β-glucosidase gene was identical to that reported by Voorhorst et al. (Voorhorst, W. G. B., Eggen, R. I. L., Luesink, E. J., and deVos, W. M. (1995) J. Bacteriol. 177, 7105-7111; GenBank accession no. U37557). The deduced amino acid sequences showed homology both with each other (46.5% identical) and with several other glycosyl hydrolases, including the β-glycosidases from Sulfolobus solfataricus, Thermotoga maritima, and Caldocellum saccharolyticum. Based on these sequence similarities, the β-mannosidase and the β-glucosidase can both be classified as family 1 glycosyl hydrolases. In addition, the β-mannosidase and β-glucosidase from P. furiosus both contained the conserved active site residues found in all family 1 enzymes. The β-mannosidase showed optimal activity at pH 7.4 and 105°C. Although the enzyme had a half-life of greater than 60 h at 90°C, it is much less thermostable than the β-glucosidase, which had a reported half-life of 85 h at 100°C. Km and Vmax values for the β-mannosidase were determined to be 0.79 mM and 31.1 μmol para-nitrophenol released/min/mg with p-nitrophenyl-β-D-mannopyranoside as substrate. The catalytic efficiency of the β-mannosidase was significantly lower than that reported for the P. furiosus β-glucosidase (5.3 versus 4, 500 s−1 mM−1 with p-nitrophenyl-β-D-glucopyranoside as substrate). The kinetic differences between the two enzymes suggest that, unlike the β-glucosidase, the primary role of the β-mannosidase may not be disaccharide hydrolysis. Other possible roles for this enzyme are discussed. Two distinct exo-acting, β-specific glycosyl hydrolases were purified to homogeneity from crude cell extracts of the hyperthermophilic archaeon Pyrococcus furiosus: a β-glucosidase, corresponding to the one previously purified by Kengen et al. (Kengen, S. W. M., Luesink, E. J., Stams, A. J. M., and Zehnder, A. J. B. (1993) Eur. J. Biochem. 213, 305-312), and a β-mannosidase. The β-mannosidase and β-glucosidase genes were isolated from a genomic library by expression screening. The nucleotide sequences predicted polypeptides with 510 and 472 amino acids corresponding to calculated molecular masses of 59.0 and 54.6 kDa for the β-mannosidase and the β-glucosidase, respectively. The β-glucosidase gene was identical to that reported by Voorhorst et al. (Voorhorst, W. G. B., Eggen, R. I. L., Luesink, E. J., and deVos, W. M. (1995) J. Bacteriol. 177, 7105-7111; GenBank accession no. U37557). The deduced amino acid sequences showed homology both with each other (46.5% identical) and with several other glycosyl hydrolases, including the β-glycosidases from Sulfolobus solfataricus, Thermotoga maritima, and Caldocellum saccharolyticum. Based on these sequence similarities, the β-mannosidase and the β-glucosidase can both be classified as family 1 glycosyl hydrolases. In addition, the β-mannosidase and β-glucosidase from P. furiosus both contained the conserved active site residues found in all family 1 enzymes. The β-mannosidase showed optimal activity at pH 7.4 and 105°C. Although the enzyme had a half-life of greater than 60 h at 90°C, it is much less thermostable than the β-glucosidase, which had a reported half-life of 85 h at 100°C. Km and Vmax values for the β-mannosidase were determined to be 0.79 mM and 31.1 μmol para-nitrophenol released/min/mg with p-nitrophenyl-β-D-mannopyranoside as substrate. The catalytic efficiency of the β-mannosidase was significantly lower than that reported for the P. furiosus β-glucosidase (5.3 versus 4, 500 s−1 mM−1 with p-nitrophenyl-β-D-glucopyranoside as substrate). The kinetic differences between the two enzymes suggest that, unlike the β-glucosidase, the primary role of the β-mannosidase may not be disaccharide hydrolysis. Other possible roles for this enzyme are discussed. DA - 1996/9// PY - 1996/9// DO - 10.1074/jbc.271.39.23749 VL - 271 IS - 39 SP - 23749-23755 J2 - Journal of Biological Chemistry LA - en OP - SN - 0021-9258 UR - http://dx.doi.org/10.1074/jbc.271.39.23749 DB - Crossref ER - TY - JOUR TI - Evaluation of matrix-assisted laser desorption ionization mass spectrometry for polymer characterization AU - Belu, A. M. AU - DeSimone, J. M. AU - Linton, R. W. AU - Lange, G. W. AU - Friedman, R. M. T2 - Journal of the American Society for Mass Spectrometry AB - A protocol for the preparation of polymeric samples for time-of-flight matrix-assisted laser desorption ionization mass spectrometry (TOF-MALDI-MS) analysis was developed. Dithranol was identified as a good matrix for polystyrene (PS), and the addition of silver for cationization of molecules was determined to be necessary. Based on this preparative method, low molecular weight samples of other polymers [polyisoprene, polybutadiene, poly(ethylene oxide), poly(methyl methacrylate), and polydimethylsiloxane] were analyzed with molecular weights up to 49 ku. The effects of laser intensity were determined to influence the molecular weight distribution of intact oligomers, most significantly for low molecular weight polymers. Linear and reflectron modes of analysis were evaluated; better signal intensity and resolution were obtained in the reflectron mode. The TOF-MALDI-MS measurements are compared with time-of-flight secondary ion mass spectrometry (TOF-SIMS) and gel permeation chromatography (GPC) for the same polymers. The Mn values calculated by TOF-MALDI-MS consistently are higher than values calculated by TOF-SIMS for all classes of polymers with molecular weights up to 8 ku. The molecular weights of the PS calculated from TOF-MALDI-MS are in good agreement with GPC (±10%). The composition of the terminal group on a polymer chain may affect the ion yields. The ion yields of intact oligomers were evaluated as a function of end group composition for both TOF-MALDI-MS and TOF-SIMS. The slight disparity of results between TOF-SIMS and TOF-MALDI-MS for the perfluoroalkyl-terminated PS suggests that the oligomers are desorbed preferentially from the surface in the TOF-SIMS analysis, rather than having an increased ionization probability. DA - 1996/1// PY - 1996/1// DO - 10.1016/1044-0305(95)00589-7 VL - 7 IS - 1 SP - 11-24 J2 - J Am Soc Mass Spectrom LA - en OP - SN - 1044-0305 1879-1123 UR - http://dx.doi.org/10.1016/1044-0305(95)00589-7 DB - Crossref ER - TY - JOUR TI - Ring-Opening Metathesis Polymerizations in Carbon Dioxide AU - Mistele, Chad D. AU - Thorp, Holden H. AU - Desimone, Joseph M. T2 - Journal of Macromolecular Science, Part A AB - Abstract The polymerization of norbornene was successfully initiated with Ru(H2O)6(tos)2 in a carbon dioxide medium. The resultant poly(norbornene) was prepared with yields and molecular weights comparable to those obtained in other solvent systems. It was also found that the cis/trans ratio of the polymer microstructure could be controlled by the addition of various amounts of methanol to the reaction mixture. A detailed account of the polymerizations is described and believed to be the first example of a ring-opening metathesis polymerization in carbon dioxide. DA - 1996/7// PY - 1996/7// DO - 10.1080/10601329608014644 VL - 33 IS - 7 SP - 953-960 J2 - Journal of Macromolecular Science, Part A LA - en OP - SN - 1060-1325 1520-5738 UR - http://dx.doi.org/10.1080/10601329608014644 DB - Crossref ER - TY - JOUR TI - Dispersion Polymerizations in Carbon Dioxide Using Siloxane-Based Stabilizers AU - Shaffer, K. A. AU - Jones, T. A. AU - Canelas, D. A. AU - DeSimone, J. M. AU - Wilkinson, S. P. T2 - Macromolecules AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTDispersion Polymerizations in Carbon Dioxide Using Siloxane-Based StabilizersK. A. Shaffer, T. A. Jones, D. A. Canelas, J. M. DeSimone, and S. P. WilkinsonView Author Information Department of Chemistry, C. B. 3290, Venable and Kenan Laboratories, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 Air Products and Chemicals, 7201 Hamilton Boulevard, Allentown, Pennsylvania 18195-1501 Cite this: Macromolecules 1996, 29, 7, 2704–2706Publication Date (Web):March 25, 1996Publication History Received10 November 1995Revised5 February 1996Published online25 March 1996Published inissue 1 January 1996https://doi.org/10.1021/ma9516798Copyright © 1996 American Chemical SocietyRequest reuse permissionsArticle Views584Altmetric-Citations149LEARN 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. 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Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (158 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Colloids,Copolymerization,Liquids,Polymerization,Silicones Get e-Alerts DA - 1996/1// PY - 1996/1// DO - 10.1021/ma9516798 VL - 29 IS - 7 SP - 2704-2706 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma9516798 DB - Crossref ER - TY - JOUR TI - Dispersion Polymerization of Styrene in Supercritical Carbon Dioxide:  Importance of Effective Surfactants AU - Canelas, D. A. AU - Betts, D. E. AU - DeSimone, J. M. T2 - Macromolecules AB - The dispersion polymerization of styrene in supercritical CO2 using amphiphilic diblock copolymers to impart steric stabilization was investigated. Lipophilic, CO2-insoluble materials can be effectively emulsified in carbon dioxide using amphiphilic diblock copolymer surfactants. The resulting high yield (>90%) of polystyrene is obtained in the form of a stable polymer colloid comprised of submicron-sized particles. The particle diameter and distribution of sizes were shown to be dependent on the nature of the stabilizing block copolymer. DA - 1996/1// PY - 1996/1// DO - 10.1021/ma951642n VL - 29 IS - 8 SP - 2818-2821 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma951642n DB - Crossref ER - TY - JOUR TI - Design of Nonionic Surfactants for Supercritical Carbon Dioxide AU - McClain, J. B. AU - Betts, D. E. AU - Canelas, D. A. AU - Samulski, E. T. AU - DeSimone, J. M. AU - Londono, J. D. AU - Cochran, H. D. AU - Wignall, G. D. AU - Chillura-Martino, D. AU - Triolo, R. T2 - Science AB - Interfacially active block copolymer amphiphiles have been synthesized and their self-assembly into micelles in supercritical carbon dioxide (CO2) has been demonstrated with small-angle neutron scattering (SANS). These materials establish the design criteria for molecularly engineered surfactants that can stabilize and disperse otherwise insoluble matter into a CO2 continuous phase. Polystyrene-b-poly(1,1-dihydroperfluorooctyl acrylate) copolymers self-assembled into polydisperse core-shell-type micelles as a result of the disparate solubility characteristics of the different block segments in CO2. These nonionic surfactants for CO2 were shown by SANS to be capable of emulsifying up to 20 percent by weight of a CO2-insoluble hydrocarbon into CO2. This result demonstrates the efficacy of surfactant-modified CO2 in reducing the large volumes of organic and halogenated solvent waste streams released into our environment by solvent-intensive manufacturing and process industries. DA - 1996/12/20/ PY - 1996/12/20/ DO - 10.1126/science.274.5295.2049 VL - 274 IS - 5295 SP - 2049-2052 J2 - Science LA - en OP - SN - 0036-8075 1095-9203 UR - http://dx.doi.org/10.1126/science.274.5295.2049 DB - Crossref ER - TY - JOUR TI - Modification of poly[(3-hydroxybutyric acid)-co-(3-hydroxyvaleric acid)] film surfaces in an oxygen low pressure plasma AU - Mas, André AU - Jaaba, Hassan AU - Schué, François AU - Bellu, Anna Maria AU - Kassis, Camille AU - Linton, Richard AU - Desimone, Joseph Mark T2 - Macromolecular Chemistry and Physics AB - Abstract Poly[(3‐hydroxybutyric acid)‐ co ‐(3‐hydroxyvaleric acid)] (91:9 mass‐%) (P(HB‐co‐9% HV)) film surfaces were modified by an oxygen plasma treatment (75 W, 50 Pa, 5 min). The number of oxygen atoms increases about 12–13% and the polar component of the surface energy increases from 6.3 to 21 mN · m −1 . However, the wettability is stable only after 60 days. Untreated and treated film surfaces are studied by means of X‐ray photoelectron spectroscopy with two different depth analyses. With storage time, the oxygen contents of the modified film is constant at a take‐off angle of 20° but decreases to the initial value at a take‐off angle of 70°. The superficial layer of the polymer film between the top of the film to a depth of 10 nm is divided into three superimposing zones. The interpretation is supported by motions of modified macromolecular chains and buried polar groups, chain cleavage and the formation of low‐molecular‐weight molecules which leads to a decrease of the glass transition temperature (plasticizer effect) and migration of short chains from the lowest modified zone toward the surface. DA - 1996/7// PY - 1996/7// DO - 10.1002/macp.1996.021970723 VL - 197 IS - 7 SP - 2331-2341 J2 - Macromol. Chem. Phys. OP - SN - 1022-1352 1521-3935 UR - http://dx.doi.org/10.1002/macp.1996.021970723 DB - Crossref ER - TY - JOUR TI - Neutron scattering characterization of homopolymers and graft-copolymer micelles in supercritical carbon dioxide AU - Chillura-Martino, D. AU - Triolo, R. AU - McClain, J.B. AU - Combes, J.R. AU - Betts, D.E. AU - Canelas, D.A. AU - DeSimone, J.M. AU - Samulski, E.T. AU - Cochran, H.D. AU - Londono, J.D. AU - Wignall, G.D. T2 - Journal of Molecular Structure AB - Superficial fluids (SCF) are becoming an attractive alternative to the liquid solvents traditionally used as polymerization media [1]. As the synthesis proceeds, a wide range of colloidal aggregates form, but there has hitherto been no way to measure such structures directly. We have applied small-angle neutron scattering (SANS) to characterize such systems, and although SCF polymerizations are carried out at high pressures, the penetrating power of the neutron beam means that typical cell windows are virtually transparent. Systems studied include polymers soluble in CO2 such as poly(1,1-dihydroperfluorooctyl acrylate) (PFOA), poly(hexafluoropropylene oxide) (PHFPO) and poly(dimethyl siloxane) (PDMS). PFOA has previously [2] been shown to exhibit a positive second virial coefficient (A2), though for PHFPO, A2 appears to be close to zero (104 A2 ⋍ 0 ± 0.2 cm3 g−2 mol). PDMS is soluble on the molecular level only in the limit of dilute solution and seems to form aggregates as the concentration increases (c > 0.01 g cm−3). Typical hydrocarbon polymers are insoluble in CO2, but it has been found that polymerizations may be accomplished via the use of a stabilizer [3]. For example, styrene has been polymerized in CO2 by means of a polystyrene-b-PFOA block copolymer surfactant, which forms micelles in CO2 and is also amenable to SANS characterization. Other amphiphilic surfactant molecules that form micelles include PFOA-g-poly(ethylene oxide) (PFOA-g-PEO) graft copolymers, which swell as the CO2 medium is saturated with water. These systems have been characterized by SANS, by taking advantage of the different contrast options afforded by substituting D2O for H2O. This paper illustrates the utility of SANS to measure molecular dimensions, thermodynamic variables, molecular weights, micelle structures etc. in supercritical CO2. DA - 1996/9// PY - 1996/9// DO - 10.1016/s0022-2860(96)09260-5 VL - 383 IS - 1-3 SP - 3-10 J2 - Journal of Molecular Structure LA - en OP - SN - 0022-2860 UR - http://dx.doi.org/10.1016/s0022-2860(96)09260-5 DB - Crossref KW - small angle neutron scattering KW - supercritical fluids KW - homopolymers KW - graft-copolymer micelles ER - TY - JOUR TI - Useful Model Systems for the Study of SRN1 Chemistry in the Synthesis of Poly(arylene ether ketone)s AU - Dukes, Katerina E. AU - Forbes, Malcolm D. E. AU - Jeevarajan, Antony S. AU - Belu, Anna M. AU - DeSimone, Joseph M. AU - Linton, Richard W. AU - Sheares, Valerie V. T2 - Macromolecules AB - Factors contributing to the occurrence of the SRN1 reaction during the synthesis of poly(arylene ether ketone)s are studied using a variety of analytical techniques. Product analysis of polymerization reactions and magnetic resonance studies on photochemical model systems were performed. The polymerization of 4,4‘-dichlorobenzophenone with 4,4‘-isopropylidenediphenol under basic conditions was run in four amide solvents: 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU), 1-methyl-2-pyrrolidinone (NMP), 1,1,3,3-tetramethylurea (TMU) and N,N ‘-dimethylacetamide (DMAc). Molecular weights of the products followed the order Mn(DMAc) > Mn(NMP) > Mn(TMU) > Mn(DMPU). Simulations of time-resolved electron paramagnetic resonance (TREPR) spectra were used to identify the radicals produced by photoinduced hydrogen atom abstraction in each of the four solvents. Transient optical absorption was used to quantify the yield of radicals produced by reaction of triplet benzophenone-d10 with each solvent. Time-of-flight secondary ion mass spectrometry of the resulting oligomers showed evidence for hydrogen-terminated chain ends. Solvated electrons were observed from the photoionization of phenolates using TREPR. The relevance of this to single electron transfer events in these solvents, or with certain aryl halide monomers for polymer synthesis, is discussed. DA - 1996/1// PY - 1996/1// DO - 10.1021/ma951381h VL - 29 IS - 9 SP - 3081-3089 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma951381h DB - Crossref ER - TY - JOUR TI - Solution Properties of a CO2-Soluble Fluoropolymer via Small Angle Neutron Scattering AU - McClain, J. B. AU - Londono, D. AU - Combes, J. R. AU - Romack, T. J. AU - Canelas, D. A. AU - Betts, D. E. AU - Wignall, G. D. AU - Samulski, E. T. AU - DeSimone, J. M. T2 - Journal of the American Chemical Society AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSolution Properties of a CO2-Soluble Fluoropolymer via Small Angle Neutron ScatteringJ. B. McClain, D. Londono, J. R. Combes, T. J. Romack, D. A. Canelas, D. E. Betts, G. D. Wignall, E. T. Samulski, and J. M. DeSimoneView Author Information Venable and Kenan Laboratories Department of Chemistry CB#3290 University of North Carolina at Chapel Hill Chapel Hill, North Carolina 27599-3290 Oak Ridge National Laboratories P.O. Box 2008, Oak Ridge, Tennessee 37831-6393 Cite this: J. Am. Chem. Soc. 1996, 118, 4, 917–918Publication Date (Web):January 31, 1996Publication History Received11 August 1995Published online31 January 1996Published inissue 1 January 1996https://doi.org/10.1021/ja952750sCopyright © 1996 American Chemical SocietyRequest reuse permissionsArticle Views477Altmetric-Citations111LEARN 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 (114 KB) Get e-AlertscloseSupporting Info (2)»Supporting Information Supporting Information SUBJECTS:Neutron scattering,Polymer solutions,Polymers,Scattering,Solvents Get e-Alerts DA - 1996/1// PY - 1996/1// DO - 10.1021/ja952750s VL - 118 IS - 4 SP - 917-918 J2 - J. Am. Chem. Soc. LA - en OP - SN - 0002-7863 1520-5126 UR - http://dx.doi.org/10.1021/ja952750s DB - Crossref ER - TY - JOUR TI - Synthesis of Poly(2,6-dimethylphenylene oxide) in Carbon Dioxide AU - Kapellen, K. K. AU - Mistele, C. D. AU - DeSimone, J. M. T2 - Macromolecules AB - ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSynthesis of Poly(2,6-dimethylphenylene oxide) in Carbon DioxideK. K. Kapellen, C. D. Mistele, and J. M. DeSimoneView Author Information CB #3290, Venable and Kenan Laboratories, Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 Cite this: Macromolecules 1996, 29, 1, 495–496Publication Date (Web):January 1, 1996Publication History Received31 August 1995Revised27 October 1995Published online1 January 1996Published inissue 1 January 1996https://doi.org/10.1021/ma951299mCopyright © 1996 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views204Altmetric-Citations35LEARN 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 (60 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Amines,Inorganic carbon compounds,Oxides,Polymers,Pyridines Get e-Alerts DA - 1996/1// PY - 1996/1// DO - 10.1021/ma951299m VL - 29 IS - 1 SP - 495-496 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma951299m DB - Crossref ER - TY - JOUR TI - XPS Studies of Fluorinated Acrylate Polymers and Block Copolymers with Polystyrene AU - Kassis, Camille M. AU - Steehler, Jack K. AU - Betts, Douglas E. AU - Guan, Zhibin AU - Romack, Timothy J. AU - DeSimone, Joseph M. AU - Linton, Richard W. T2 - Macromolecules AB - X-ray photoelectron spectroscopy (XPS) has been used to investigate the surface characteristics of various novel fluorinated acrylate homopolymers [1,1-dihydroperfluorooctyl acrylate (PFOA), 1,1-dihydroperfluorooctyl methacrylate (PFOMA), 1,1,2,2-tetrahydroperfluorooctyl acrylate (PTAN)] as well as diblock copolymers consisting of both a fluorocarbon block of PFOA and a hydrocarbon block of polystyrene (PS). This technique allows nondestructive depth profiling of the top ∼100 Å of a material, providing both elemental composition and chemical state information. Due to the low surface energy of the fluorinated species, its enhanced presence on the surface is of importance in any potential applications. Angle-dependent XPS surface studies were conducted on polymer thick films to monitor surface segregation of the fluorinated component as a function of depth. Fluorine and the fluorine-containing constituents are surface enriched relative to carbon and oxygen from the acrylate portions of the polymers. This effect also occurs in the diblock copolymers, where the PFOA block prefers the polymer−air interface. Furthermore, this surface segregation is enhanced when the samples are thermally annealed. Also, the quantitative XPS data reveal other subtleties in the overall polymer structures, such as extent of chain branching in PFOA, PFOMA, and the diblock copolymers and the slight variations in average fluorine-containing side chain lengths in PTAN. DA - 1996/1// PY - 1996/1// DO - 10.1021/ma951782x VL - 29 IS - 9 SP - 3247-3254 J2 - Macromolecules LA - en OP - SN - 0024-9297 1520-5835 UR - http://dx.doi.org/10.1021/ma951782x DB - Crossref ER - TY - CHAP TI - The importance of surfactants for polymerizations in carbon dioxide AU - Betts, D.E. AU - McClain, J.B. AU - DeSimone, J.M. T2 - High Pressure Chemical Engineering, Proceedings of the 3rd International Symposium on High Pressure Chemical Engineering AB - Publisher Summary This chapter describes the effects of various surfactant and stabilizer systems as they apply to polymerizations in CO 2 . For CO 2 to be an effective continuous phase for polymerizations, heterogeneous reaction systems must necessarily be developed analogous to classical emulsion, inverse emulsion, dispersion, suspension, and precipitation polymerization processes. With some highly reactive monomers, such as acrylic acid and tetrafluoroethylene, free-radical precipitation polymerization can afford polymers with high yields and molecular weight. However, many industrial monomers require the utilization of surfactant stabilized reaction conditions. This chapter discusses the utilization of nonionic—homopolymer, block copolymer, and reactive macromonomer—surfactants consisting of covalently bound CO 2 -philic and CO 2 -phobic segments in the dispersion polymerization of various CO 2 -insoluble polymers. These reactions produce a stabilized polymer colloid in CO 2 solution and dry, free flowing powders after isolation. PY - 1996/// DO - 10.1016/s0921-8610(96)80006-9 SP - 23-30 OP - PB - Elsevier SN - 9780444824752 UR - http://dx.doi.org/10.1016/s0921-8610(96)80006-9 DB - Crossref ER - TY - JOUR TI - Polymer synthesis and characterization in liquid / supercritical carbon dioxide AU - Cooper, Andrew I AU - DeSimone, Joseph M T2 - Current Opinion in Solid State and Materials Science AB - The use of carbon dioxide as an inert solvent has emerged recently as an important development in polymer chemistry. The past year has seen major advances in the synthesis of a variety of polymeric materials in carbon dioxide. At the same time complementary studies have successfully elucidated the physical behavior of a range of polymers in carbon dioxide solution. Herein we review both synthetic and physical studies that are defining the scope of this approach. DA - 1996/12// PY - 1996/12// DO - 10.1016/s1359-0286(96)80100-8 VL - 1 IS - 6 SP - 761-768 J2 - Current Opinion in Solid State and Materials Science LA - en OP - SN - 1359-0286 UR - http://dx.doi.org/10.1016/s1359-0286(96)80100-8 DB - Crossref ER - TY - JOUR TI - Effect of Surface Active Sites on Adsorption of Associating Chain Molecules in Pores: a Monte Carlo Study AU - Vega, Lourdes F. AU - Müller, Erich A. AU - Rull, Luis F. AU - Gubbins, Keith E. T2 - Adsorption DA - 1996/// PY - 1996/// DO - 10.1007/bf00127099 VL - 2 IS - 1 SP - 59-68 SN - 0929-5607 1572-8757 UR - http://dx.doi.org/10.1007/bf00127099 ER - TY - JOUR TI - Phase Equilibria Calculations with a Modified SAFT Equation of State. 2. Binary Mixtures of n-Alkanes, 1-Alkanols, and Water AU - Kraska, Thomas AU - Gubbins, Keith E. T2 - Industrial & Engineering Chemistry Research AB - The Lennard-Jones−statistical association fluid theory (LJ−SAFT) is applied to binary mixtures containing one self-associating and one nonassociating substance. The binary systems studied here are n-alkane/n-alkane, 1-alkanol/n-alkane, and water/n-alkane mixtures. For cases where the dipole−dipole term is needed, the influence of induction is also investigated. The results with LJ−SAFT exhibit better agreement with experimental data than SAFT. This improvement is due to the exchange of the hard-sphere reference system by the LJ reference system. DA - 1996/1// PY - 1996/1// DO - 10.1021/ie960233s VL - 35 IS - 12 SP - 4738-4746 SN - 0888-5885 1520-5045 UR - http://dx.doi.org/10.1021/ie960233s ER - TY - CONF TI - Monte Carlo Simulations of Adsorption of Nitrogen/Methane Mixtures in Zeolites AU - Rinaldi, C.M. AU - Estevez, L.A. AU - Nicholson, D. AU - Maddox, M. AU - Gubbins, K.E. T2 - Fifth World Congress of Chemical Engineering C2 - 1996/// C3 - Proceedings of the Fifth World Congress of Chemical Engineering CY - San Diego, CA DA - 1996/// PY - 1996/7// PB - American Institute of Chemical Engineers ER - TY - JOUR TI - Reply to Comment on Molecular Dynamics Study of Entangled Hard Chain Fluids AU - Smith, S.W. AU - Hall, C.K. AU - Freeman, B.D. T2 - Physical Review Letters DA - 1996/// PY - 1996/// VL - 76 SP - 4449 ER - TY - JOUR TI - Solute Excluded Volume Effects on the Stability of Globular Proteins: A Statistical Thermodynamic Theory AU - Zhou, Y. AU - Hall, C.K. T2 - Biopolymers DA - 1996/2// PY - 1996/2// VL - 38 IS - 2 SP - 273-284 ER - TY - JOUR TI - Thermochemical and chemical kinetic data for fluorinated hydrocarbons AU - Burgess, D. R. AU - Zachariah, M. R. AU - Tsang, W. AU - Westmoreland, Phillip T2 - Progress in Energy and Combustion Science AB - A comprehensive, detailed chemical kinetic mechanism was developed and is presented for C1 and C2 fluorinated hydrocarbon destruction and flame suppression. Existing fluorinated hydrocarbon thermochemistry and kinetics were compiled from the literature and evaluated. For species where no or incomplete thermochemistry was available, these data were calculated through application of ab initio molecular orbital theory. Group additivity values were determined consistent with experimental and ab initio data. For reactions where no or limited kinetics were available, these data were estimated by analogy to hydrocarbon reactions, by using empirical relationships from other fluorinated hydrocarbon reactions, by ab initio transition state calculations, and by application of RRKM and QRRK methods. The chemistry was modeled considering different transport conditions (plug flow, premixed flame, opposed flow diffusion flame) and using different fuels (methane, ethylene), equivalence ratios, agents (fluoromethanes, fluoroethanes) and agent concentrations. This report provides a compilation and analysis of the thermochemical and chemical kinetic data used in this work. DA - 1996/// PY - 1996/// DO - 10.1016/0360-1285(95)00009-7 VL - 21 IS - 6 SP - 453–529 ER - TY - CHAP TI - Simulation Studies of Pore Blocking Hysteresis in Model Porous Carbon Networks AU - Maddox, M. W. AU - Lastoskie, C. M. AU - Quirke, N. AU - Gubbins, K. E. T2 - The Kluwer International Series in Engineering and Computer Science AB - Grand canonical Monte Carlo (GCMC) and grand canonical molecular dynamics (GCMD) simulations are used to study the adsorption and desorption of spherical Lennard-Jones nitrogen in model porous carbon networks at 77 K. IUP AC type IV isotherms are produced with hysteresis loops of subclass H4. This type of hysteresis loop is shown to be the result of pore blocking effects. Capillary evaporation from a large pore connected to the bulk reservoir by much narrower, fluid filled pores is shown to arise from spinodal decomposition of the condensed fluid in the larger pore. PY - 1996/// DO - 10.1007/978-1-4613-1375-5_71 SP - 571-578 OP - PB - Springer US SN - 9781461285946 9781461313755 UR - http://dx.doi.org/10.1007/978-1-4613-1375-5_71 DB - Crossref ER - TY - CHAP TI - Adsorption Isotherms of Associating Fluids in Slit-Like Pores. A Monte Carlo Simulation Study AU - Vega, Lourdes F. AU - Müller, Erich A. AU - Rull, Luis F. AU - Gubbins, Keith E. T2 - The Kluwer International Series in Engineering and Computer Science AB - We report a molecular simulation (Grand Canonical and Gibbs Ensemble Monte Carlo) study of the influence of associating wall sites on adsorption. The fluids considered are modeled on water and self-associating chain molecules, and the adsorbent is a carbon with slit pores, with varying density and arrangement of the active surface sites. The adsorption is much enhanced by the presence of the surface sites, and is sensitive to both the density and geometric arrangement of the sites on the surface. PY - 1996/// DO - 10.1007/978-1-4613-1375-5_124 SP - 993-1000 OP - PB - Springer US SN - 9781461285946 9781461313755 UR - http://dx.doi.org/10.1007/978-1-4613-1375-5_124 DB - Crossref ER - TY - CHAP TI - Molecular Simulation of Pure Fluid and Binary Mixture Adsorption in Buckytubes and MCM-41 AU - Maddox, M. W. AU - Gubbins, K. E. T2 - The Kluwer International Series in Engineering and Computer Science AB - Grand canonical Monte Carlo (GCMC) molecular simulation is used to study the adsorption of argon in model buckytubes and an equimolar argon/nitrogen mixture in a model MCM-41 pore. The critical buckytube pore diameter above which argon exhibits first-order condensation at 77 K is determined to be between 1.5 nm and 2.0 nm. At pressures below 0.0002 atm, nitrogen is selectively adsorbed into a 1.9 nm diameter MCM-41 pore at 77 K. At higher pressures an interesting reversal of selectivity is demonstrated and argon is preferentially adsorbed. PY - 1996/// DO - 10.1007/978-1-4613-1375-5_70 SP - 563-570 OP - PB - Springer US SN - 9781461285946 9781461313755 UR - http://dx.doi.org/10.1007/978-1-4613-1375-5_70 DB - Crossref ER - TY - CHAP TI - Removal of Trace Pollutants by Adsorption: Density Functional Theory and Monte Carlo Simulation AU - Sowers, Susanne L. AU - Gubbins, Keith E. T2 - The Kluwer International Series in Engineering and Computer Science AB - We report calculations, based on density functional theory and molecular simulations, for a simple model of the selective adsorption in carbon pores for three trace contaminants, modeled as CCl4, CF4 and SO2, from nitrogen streams at 300K. The influence of gas pressure, pore width and concentration is studied. In each case there is an optimal pore width and pressure for which the selectivity is greatly enhanced. The pore size distribution of real sorbents is found to significantly degrade the selectivity. The density functional theory is in very good agreement with the simulation results for these infinitely dilute mixtures. PY - 1996/// DO - 10.1007/978-1-4613-1375-5_107 SP - 855-863 OP - PB - Springer US SN - 9781461285946 9781461313755 UR - http://dx.doi.org/10.1007/978-1-4613-1375-5_107 DB - Crossref ER - TY - CHAP TI - Molecular Simulations and Industrial Applications AU - Gubbins, K.E. AU - Quirke, N. T2 - Molecular Simulation and Industrial Applications: Methods, Examples and Prospects PY - 1996/// SP - 1–69 PB - Gordon & Breach Science Publisher ER - TY - BOOK TI - Molecular Simulation and Industrial Applications: Methods, Applications and Prospects A3 - Gubbins, K.E. A3 - Quirke, N. DA - 1996/// PY - 1996/// PB - Gordon & Breach ER - TY - JOUR TI - Grand canonical Monte Carlo simulation for nitrogen adsorption in graphitic slit micropores: effect of interlayer distance AU - Suzuki, T. AU - Kaneko, K. AU - Setoyama, N. AU - Maddox, M. AU - Gubbins, K. T2 - Carbon AB - Adsorption isotherms of N2 by slit-shaped graphitic micropores at 77 K were simulated using grand canonical Monte Carlo (GCMC) simulation and compared the simulated isotherms with experimental adsorption isotherms of N2 on pitch-based activated carbon fibers. The pore was modeled as the slit space between parallel smooth graphite surfaces. The concept of the effective pore width which can be determined experimentally was used for the simulation. The effect of the layer distance (d002) of the graphitic structure on the simulated N2 adsorption isotherm was examined. The observed d002 of activated carbon fiber (ACF) well simulated the experimental result. DA - 1996/// PY - 1996/// DO - 10.1016/0008-6223(96)00049-8 VL - 34 IS - 7 SP - 909-912 J2 - Carbon LA - en OP - SN - 0008-6223 UR - http://dx.doi.org/10.1016/0008-6223(96)00049-8 DB - Crossref KW - grand canonical Monte Carlo simulation KW - N-2 absorption KW - activated carbon fiber KW - micropore ER - TY - JOUR TI - Phase Equilibria Calculations with a Modified SAFT Equation of State. 1. Pure Alkanes, Alkanols, and Water AU - Kraska, Thomas AU - Gubbins, Keith E. T2 - Industrial & Engineering Chemistry Research AB - The phase equilibria of the n-alkanes and the 1-alkanols have been calculated with the Lennard-Jones−SAFT (statistical association fluid theory) equation of state of Müller and Gubbins. This equation includes contributions from a dipole−dipole term, a modified association term, a chain term, and a Lennard-Jones term to account for monomer dispersion and overlap interactions. The influence of electrostatic forces due to the dipole moment has been investigated, and a simple treatment of the polarizability has been tested. It is shown by comparison with some sample calculations based on the renormalized perturbation theory that this approach is reasonable. The calculated phase equilibria are in good agreement with experimental data. The deviation between calculated and experimental data is significantly lower than for the original SAFT equation of state and a recently published chemical theory. DA - 1996/1// PY - 1996/1// DO - 10.1021/ie9602320 VL - 35 IS - 12 SP - 4727-4737 J2 - Ind. Eng. Chem. Res. LA - en OP - SN - 0888-5885 1520-5045 UR - http://dx.doi.org/10.1021/ie9602320 DB - Crossref ER - TY - JOUR TI - Molecular Simulations of Phase Transitions in Pores AU - Gubbins, Keith E. AU - Sliwinska-Bartkowiak, Malgorzata AU - Suh, Soong-Hyuck T2 - Molecular Simulation AB - Abstract Methods for simulating phase transitions in narrow pores are reviewed, and the advantages and disadvantages of different techniques are discussed. Examples are given of applications to vapor-liquid, liquid-liquid, melting and freezing, solid-solid and layering transitions. While there has been a considerable body of simulation work on vapor-liquid, wetting and layering transitions for simple fluids and pore geometries, much remains to be done on more complex geometries and network effects, on heterogeneous surfaces, and on liquid-liquid, melting and solid-solid transitions in pores. DA - 1996/8// PY - 1996/8// DO - 10.1080/08927029608024116 VL - 17 IS - 4-6 SP - 333-367 J2 - Molecular Simulation LA - en OP - SN - 0892-7022 1029-0435 UR - http://dx.doi.org/10.1080/08927029608024116 DB - Crossref KW - phase transitions KW - pores KW - capillary condensation KW - layering transitions KW - melting KW - freezing KW - liquid-liquid equilibria ER - TY - JOUR TI - Thermodynamic scaling Gibbs ensemble Monte Carlo: a new method for determination of phase coexistence properties of fluids AU - Kiyohara, Kenji AU - Spyriouni, Theodora AU - Gubbins, Keith AU - Panagiotopoulos, Athanassios T2 - Molecular Physics AB - Valleau's thermodynamic scaling Monte Carlo conceptis combined with the Gibbs ensemble method for phase coexistence calculations, and phase co-existence properties of several Hamiltonians (potential models) at many temperatures are obtained in a single simulation. The theoretical formulation of the method is presented in detail. An application to the (n – 6) Lennard-Jones family of potentials is demonstrated. The combined method is found to be more efficient than the conventional Gibbs ensemble method when properties of related potential models at many thermodynamic states are of interest. Possible extensions of the combined methodology to mixtures, intermolecular potential model development, and multisegment systems that require configurational-bias sampling are discussed. DA - 1996/11/1/ PY - 1996/11/1/ DO - 10.1080/00268979609482517 VL - 89 IS - 4 SP - 965-974 J2 - Mol. Phys. LA - en OP - SN - 0026-8976 UR - http://dx.doi.org/10.1080/00268979609482517 DB - Crossref ER - TY - JOUR TI - Molecular Simulation of Fluid Phase Equilibria and Adsorption AU - Gubbins, K. E. T2 - Revue de l'Institut Français du Pétrole DA - 1996/1// PY - 1996/1// DO - 10.2516/ogst:1996005 VL - 51 IS - 1 SP - 59-72 J2 - Rev. Inst. Fr. Pét. OP - SN - 0020-2274 UR - http://dx.doi.org/10.2516/ogst:1996005 DB - Crossref ER - TY - JOUR TI - Separation of carbon dioxide–methane mixtures by adsorption: Effects of geometry and energetics on selectivity AU - Nicholson, David AU - Gubbins, Keith E. T2 - The Journal of Chemical Physics AB - The adsorption of methane–carbon dioxide mixtures in micropores having either slit or cylindrical geometries, and different adsorption energies, has been studied using molecular simulation. The pore models were constructed from close packed layers of simple atoms whose Lennard-Jones interaction parameters could be varied. For realistic choices of the adsorbent parameters, adsorption selectivity outside the molecular sieving regime was found to vary over a range between about 4 and about 1/4, denoting a preference for either CO2 or for methane, depending on geometry and choice of parameters. The variations in selectivity are interpreted in terms of a balance between energetic factors, including adsorbate–adsorbent interactions and cooperative adsorbate interactions, and entropic factors associated with the constraints on rotational freedom of the CO2 molecule imposed mainly by the geometry of the pore spaces. DA - 1996/5/22/ PY - 1996/5/22/ DO - 10.1063/1.471527 VL - 104 IS - 20 SP - 8126-8134 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.471527 DB - Crossref ER - TY - JOUR TI - Theoretical Studies on VPI-5. 2. Energy Decomposition Analysis of the Hydrophilicity AU - Kitao, Osamu AU - Gubbins, Keith E. T2 - The Journal of Physical Chemistry AB - The hydrophilic property of VPI-5 was investigated using cluster models by an ab initio MO method. The four cluster models of Al(OH)4 studied differ from each other in the original locations of the aluminum atom and in whether they are for the hydrate or the dehydrate. Only one model, which has an aluminum site at the center of the fused 4-membered rings in the hydrated VPI-5, can adsorb a water molecule with an attractive interaction energy of over 25 kcal/mol. The other models show only repulsive interaction energies. The origin of the hydrophilicity was investigated by an energy decomposition analysis. The analysis concluded that (1) for three of the four kinds of Al sites, oxygen atoms around the Al atom prevent any water molecule from coming to the Al site by a large exchange interaction, and (2) for one kind of the Al site, electrostatic and charge transfer terms between the oxygen atom of the water molecule and the Al atom are stronger than the exchange interaction mentioned above. Consequently, the Al site works well as a Lewis acid site. DA - 1996/1// PY - 1996/1// DO - 10.1021/jp952344v VL - 100 IS - 30 SP - 12424-12430 J2 - J. Phys. Chem. LA - en OP - SN - 0022-3654 1541-5740 UR - http://dx.doi.org/10.1021/jp952344v DB - Crossref ER - TY - JOUR TI - Molecular dynamics simulation of hydrogen bonding in monoethanolamine AU - Button, J.K. AU - Gubbins, K.E. AU - Tanaka, H. AU - Nakanishi, K. T2 - Fluid Phase Equilibria AB - We present the results of NVT molecular dynamics simulation for pure liquid monoethanolamine for several temperatures and densities corresponding to states of vapour-liquid equilibrium. We analyze radial distribution functions for information about hydrogen bonding. DA - 1996/3// PY - 1996/3// DO - 10.1016/0378-3812(95)02902-8 VL - 116 IS - 1-2 SP - 320-325 J2 - Fluid Phase Equilibria LA - en OP - SN - 0378-3812 UR - http://dx.doi.org/10.1016/0378-3812(95)02902-8 DB - Crossref ER - TY - JOUR TI - Adsorption of Water on Activated Carbons:  A Molecular Simulation Study AU - Müller, Erich A. AU - Rull, Luis F. AU - Vega, Lourdes F. AU - Gubbins, Keith E. T2 - The Journal of Physical Chemistry AB - We report a molecular simulation study for a model of water adsorption on nonporous and porous activated carbons. The grand canonical Monte Carlo method is used, and the temperature is fixed at 300 K. Water molecules are modeled as a Lennard-Jones sphere with four square-well sites to account for the hydrogen bonding. The carbon surfaces consist of planar graphite sheets, with active chemical sites on the surface modeled as square-well sites. The effect of the density and geometric arrangement of the active sites on the surface is studied. Both macroscopic properties (particularly adsorption isotherms) and molecular configurations are obtained. The adsorption mechanism for water on such surfaces is markedly different from that of simple nonassociating molecules such as hydrocarbons or nitrogen. In contrast to the usual buildup of adsorbed layers on the surface, water adsorption is characterized by the formation of peculiar three-dimensional water clusters and networks, whose formation relies on a cooperative effect involving both fluid−fluid interactions and fluid−solid ones with suitably placed active sites. Both the density and arrangement of the sites on the surface have a pronounced effect on the adsorption. Capillary condensation is observed only for low densities of active sites; for higher densities, continuous filling occurs. DA - 1996/1// PY - 1996/1// DO - 10.1021/jp952233w VL - 100 IS - 4 SP - 1189-1196 J2 - J. Phys. Chem. LA - en OP - SN - 0022-3654 1541-5740 UR - http://dx.doi.org/10.1021/jp952233w DB - Crossref ER - TY - JOUR TI - Molecular simulation of binary mixture adsorption in buckytubes and MCM-41 AU - Maddox, M. W. AU - Sowers, S. L. AU - Gubbins, K. E. T2 - Adsorption DA - 1996/// PY - 1996/// DO - 10.1007/bf00127095 VL - 2 IS - 1 SP - 23-32 J2 - Adsorption LA - en OP - SN - 0929-5607 1572-8757 UR - http://dx.doi.org/10.1007/bf00127095 DB - Crossref KW - GCMC KW - DFT KW - adsorption KW - MCM-41 KW - buckytube KW - simulation ER - TY - JOUR TI - The Effects of Salts on the Lower Consolute Boundary of a Nonionic Micellar Solution AU - Kenkare, Paresh U. AU - Hall, Carol K. AU - Kilpatrick, Peter K. T2 - Journal of Colloid and Interface Science AB - A molecular model based in statistical thermodynamics is used to study salt effects on the lower consolute boundary of the aqueous non-ionic surfactant C8E5. The C8E5micelles are modeled as hard spheres interacting via a temperature-dependent Yukawa attraction and the salt ions are modeled as positively and negatively charged hard spheres interacting via a Coulombic potential. The excess thermodynamic properties due to the Coulombic and Yukawa potentials are evaluated using the analytical solutions to the Ornstein–Zernike equation obtained for the mean spherical approximation closure. The Yukawa parameters for the micelle–micelle attractions are determined by fitting the theoretical phase diagram for a pure Yukawa fluid to the experimental lower consolute boundary for a salt-free C8E5micelle–water solution. Ion–solvent interactions are indirectly accounted for by using previously determined adjusted values for the cation size and the dielectric constant of the medium. We evaluate theoretical coexistence curves for the C8E5micelle–salt–water mixtures in the temperature–micelle volume fraction and temperature–salt molarity planes. We calculate the changes in the lower critical solution temperature (LCST) for the C8E5micelle–salt–water mixture as a function of salt concentration for the salts NaF, NaCl, NaBr, NaI, and Na2SO4and compare the trends seen with experiments. When ion–solvent interactions are indirectly accounted for, the theory correctly predicts the salting-out trends exhibited by NaF, NaCl, and NaBr. For the 1:2 salt (Na2SO4), charge effects resulting from the higher charge on the ions play a more important role in salting-out than ion–solvent interactions do. The theory, however, cannot predict the salting-in phenomena exhibited by NaI, thus indicating that salting-in is the result of variations in the intermicellar attraction as a function of the salt type and salt concentration. The theoretical results also indicate that excluded-volume forces resulting from the different sizes of the salt ions cannot alone account for the salting-in and salting-out phenomena seen in aqueous nonionic micellar solutions. DA - 1996/12// PY - 1996/12// DO - 10.1006/jcis.1996.0641 VL - 184 IS - 2 SP - 456-468 J2 - Journal of Colloid and Interface Science LA - en OP - SN - 0021-9797 UR - http://dx.doi.org/10.1006/jcis.1996.0641 DB - Crossref KW - micelles KW - phase separation KW - salting-in KW - salting-out KW - intermicellar potential KW - cloud point temperature KW - lower consolute boundary ER - TY - JOUR TI - Modeling of phase separation in PEG–salt aqueous two-phase systems AU - Kenkare, Paresh U. AU - Hall, Carol K. T2 - AIChE Journal AB - Abstract A molecular model based on the integral equation theory of statistical thermodynamics is used to study phase separation in PEG–salt aqueous two‐phase systems. PEG molecules are modeled as hard spheres that attract each other through a temperaturedependent Yukawa potential, which mimics the effect of PEG–water hydrogen bonding on the attraction between PEG molecules. The salt ions are modeled as charged hard spheres interacting through a Coulombic potential. Excess thermodynamic properties due to Coulombic and Yukawa interactions are calculated by analytical solutions to the Ornstein–Zernike equation for the mean spherical approximation closure. Yukawa parameters for PEG–PEG interactions are determined by fitting the theoretical phase diagram for a pure Yukawa fluid to the experimental phase diagram for a PEG–water mixture. The model predicts experimentally observed trends: increasing the temperature increases the slope and length of the tie lines; increasing the PEG molecular weight increases the miscibility gap; and increasing the anion charge lowers the salt concentration at which phase separation occurs. Theoretical results allow us to infer the relative importance of ion–PEG interactions, ion–solvent interactions, and the interpenetrable nature of PEG molecules on the phase separation in PEG–salt aqueous two‐phase systems. DA - 1996/12// PY - 1996/12// DO - 10.1002/aic.690421220 VL - 42 IS - 12 SP - 3508-3522 J2 - AIChE J. LA - en OP - SN - 0001-1541 1547-5905 UR - http://dx.doi.org/10.1002/aic.690421220 DB - Crossref ER - TY - JOUR TI - First-Order Disorder-to-Order Transition in an Isolated Homopolymer Model AU - Zhou, Yaoqi AU - Hall, Carol K. AU - Karplus, Martin T2 - Physical Review Letters AB - The thermodynamic behavior of an isolated freely jointed homonuclear square-well 64mer chain is studied by discontinuous molecular dynamics simulations. It is shown that there are three transitions that can be described as gas-liquid, liquid-solid, and solid-solid polymorphic transitions. The liquid-solid-like transition is a first-order (two-state) disorder-to-order transition. Implications of the results for protein folding are briefly discussed. DA - 1996/9/23/ PY - 1996/9/23/ DO - 10.1103/physrevlett.77.2822 VL - 77 IS - 13 SP - 2822-2825 J2 - Phys. Rev. Lett. LA - en OP - SN - 0031-9007 1079-7114 UR - http://dx.doi.org/10.1103/physrevlett.77.2822 DB - Crossref ER - TY - JOUR TI - Equilibrium conformations and dynamic relaxation of double‐tethered chain molecules at an impenetrable interface AU - Gulati, Harpreet S. AU - Hall, Carol K. AU - Jones, Ronald L. AU - Spontak, Richard J. T2 - The Journal of Chemical Physics AB - In this work, the static conformational properties and dynamic relaxation behavior of monolayers of chain molecules grafted at both ends (polymer ‘‘loops’’) to an impenetrable plane are investigated utilizing off-lattice discontinuous molecular dynamics (DMD) simulations. The conformational properties observed from DMD simulation are compared to the results of a previous on-lattice bond fluctuation (BF) study. This provides a unique opportunity to decouple the effects of excluded volume, chain flexibility and interparticle interactions, since these effects are treated differently in the two simulation methods. Static equilibrium properties of the looped chain layers determined from the DMD and BF models are in qualitative agreement with each other and with self-consistent field (SCF) predictions for brushes of N/2 repeat units. By allowing the chain anchors to move laterally along the interfacial plane, the effect of annealing on layer properties is also investigated. The characteristic relaxation time of the annealed looped chains, discerned from radius of gyration autocorrelation functions, obeys a scaling relationship of the form τ∼N3σ4/3, where σ is the surface density of the tethered chain ends. The lateral self-diffusion coefficient of the chains during annealing is also measured, with lateral diffusivity scaling as Nασβ. The exponents α and β undergo a smooth transition from α≊−4/3, β≊−4/3 at low densities to α≊−2, β≊−2 at high densities. Both relaxation times and lateral diffusivity exhibit different density scaling than brushes with N/2 repeat units. DA - 1996/11// PY - 1996/11// DO - 10.1063/1.472554 VL - 105 IS - 17 SP - 7712-7722 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.472554 DB - Crossref ER - TY - JOUR TI - Binary hard chain mixtures. I. Generalized Flory equations of state AU - Wichert, John M. AU - Gulati, Harpreet S. AU - Hall, Carol K. T2 - The Journal of Chemical Physics AB - In this series of two papers we study the thermodynamics of binary hard chain mixtures. Here, a generalized Flory-dimer (GF-D) equation of state is derived for binary hard chain mixtures composed of chains of variable length and segment diameter. Compressibility factors predicted by the GF-D equation of state developed here and by the previously derived generalized Flory equation of state are compared to previous Monte Carlo results for hard monomer/hard chain mixtures, and to new molecular dynamics (MD) hard monomer/hard chain and hard chain/hard chain mixture simulation results. Compared to the MD simulations, the GF-D theory is found to be quite accurate, with an average error of about 3% at liquid-like densities. DA - 1996/11// PY - 1996/11// DO - 10.1063/1.472550 VL - 105 IS - 17 SP - 7669-7682 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.472550 DB - Crossref ER - TY - JOUR TI - Estimation of mutual diffusion coefficients in polymer/penetrant systems using nonequilibrium molecular dynamics simulations AU - Sunderrajan, Suresh AU - Hall, Carol K. AU - Freeman, Benny D. T2 - The Journal of Chemical Physics AB - Experimental studies of the diffusion of small molecules in polymers typically report mutual diffusivities while simulation studies report tracer diffusivities. The Darken equation has been used to relate measured mutual diffusivities to calculated tracer diffusivities. The current study uses grand canonical molecular dynamics (GCMD) to simulate a gradient in chemical potential and calculate the mutual diffusivity in a polymer/penetrant system. The penetrants are modeled as hard spheres while the polymer is modeled as a collection of stationary hard chains. Penetrant mutual diffusivity is a function of two competing factors, a thermodynamic factor and a friction factor. An increase in the chemical potential of the penetrant tends to increase the diffusivity, the thermodynamic factor effect, while a corresponding increase in the number of particles within the system tends to decrease the diffusivity, the friction factor effect. Mutual diffusivity differs from penetrant tracer diffusivity by almost an order of magnitude. Mutual diffusivities do not obey the Darken relation for the simulation model used in this study. DA - 1996/7/22/ PY - 1996/7/22/ DO - 10.1063/1.472021 VL - 105 IS - 4 SP - 1621-1632 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.472021 DB - Crossref ER - TY - JOUR TI - Corrections for analytical gas-permeation models for separation of binary gas mixtures using membrane modules AU - Smith, S.W. AU - Hall, C.K. AU - Freeman, B.D. AU - Rautenbach, R. T2 - Journal of Membrane Science AB - Corrected solutions for analytical models, orginally presented by Rautenbach and Dahm [1], for membrane-based binary gas separation are presented. These models are based on constant pressure in the feed and permeate streams and perfect-mixing in the permeate stream. A comparison of these models with more complete numerical solutions suggests that the analytical models provide excellent short-cut, preliminary design information. The analytical solutions may also be used to assist convergence of more complete numerical methods. DA - 1996/9// PY - 1996/9// DO - 10.1016/0376-7388(96)00128-7 VL - 118 IS - 2 SP - 289-294 J2 - Journal of Membrane Science LA - en OP - SN - 0376-7388 UR - http://dx.doi.org/10.1016/0376-7388(96)00128-7 DB - Crossref KW - fiber membranes KW - gas separation KW - membrane modeling ER - TY - JOUR TI - Computer simulation study of the approximations associated with the generalized Flory theories AU - Kumar, Sanat K. AU - Szleifer, Igal AU - Hall, Carol K. AU - Wichert, John M. T2 - The Journal of Chemical Physics AB - The chain increment method and configurational bias Monte Carlo methods are used to test the approximations made in the derivation of the generalized Flory-Dimer (GF-D) theory for tangent hard sphere chains. Insertion probabilities and residual chemical potentials are calculated for hard chain fluids containing chains of length n=4, 8, 16, and 32 at monomer densities, ρM, up to 0.8. We find that the largest errors in the GF-D theory are those associated with assuming that the probability of inserting a monomer into a chain fluid is approximately equal to the probability of inserting a monomer into a monomer fluid, as predicted by the Carnahan–Starling equation of state. The errors in the incremental compressibility factor of the second segment associated with assuming that the conditional probability of inserting a second bead next to the first bead in a chain fluid is approximately equal to the probability of inserting a second bead next to the first bead in a dimer fluid as predicted by combining the Carnahan–Starling and Tildesley–Streett equations of state are relatively small. Consistent with the findings of Mooij and Frenkel, we find that these two approximations lead to an overprediction of the incremental contributions to the compressibility factor. Despite the overprediction of the incremental contributions to the compressibility factor of the first segment, the GF-D equation of state accurately predicts the compressibility of hard chains; this accuracy is traced to (1) the insensitivity of the compressibility factor to errors in the insertion probability and (2) cancellation of errors in the incremental compressibility factor of the first segment with small cumulative errors in the incremental compressibility factors of the third and subsequent segments. DA - 1996/6/8/ PY - 1996/6/8/ DO - 10.1063/1.471617 VL - 104 IS - 22 SP - 9100-9110 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.471617 DB - Crossref ER - TY - JOUR TI - Generalized Flory equations of state for hard heteronuclear chain molecules AU - Gulati, Harpreet S. AU - Wichert, John M. AU - Hall, Carol K. T2 - The Journal of Chemical Physics AB - The generalized Flory (GF) and generalized Flory-dimer (GFD) equations of state have been extended to fluids containing hard heteronuclear chain-like molecules. Compressibility factor expressions have been derived for block, alternating and random ‘‘copolymer’’ fluids. The effect of composition and the relative size of the segments of a heteronuclear chain on the compressibility factor are studied. We have also performed molecular dynamics computer simulations on these systems using an extension of Rapaport’s algorithm in which the chains are effectively treated as hard spheres of different sizes held together by invisible strings. The compressibility factors predicted by the GFD theory for heteronuclear chain fluids are in very good agreement with our computer simulation results. The predictions of Chiew’s Percus Yevick theory are also in very good agreement with our computer simulation results on block copolymers. DA - 1996/4// PY - 1996/4// DO - 10.1063/1.471149 VL - 104 IS - 13 SP - 5220-5233 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.471149 DB - Crossref ER - TY - JOUR TI - Molecular dynamics study of entangled hard‐chain fluids AU - Smith, Steven W. AU - Hall, Carol K. AU - Freeman, Benny D. T2 - The Journal of Chemical Physics AB - By applying efficient computational algorithms to the simplest off-lattice polymer model–the freely-jointed tangent hard-sphere chain–we have been able to perform molecular dynamics simulations long enough to probe chain dynamics in the entangled regime. Chain lengths range from 8 to 192 segments while volume fractions range from 0.3 to 0.45. Analysis of the mean-square displacement (MSD), Rouse modes, scattering functions, and end-to-end vector correlations provides information about chain motion. Chain dynamics are compared with predictions of the Rouse model for short chains and the tube model of Doi and Edwards for long chains. The mean-square displacement for the inner segments of the longest chains are consistent with predictions of the tube model, reproducing the three scaling regimes that are postulated to occur. In addition, anomalous diffusive behavior in the atomic MSD of the inner segments is observed at long times as the inner segments cross over into the free diffusion limit. Rouse-mode autocorrelation functions decay non-exponentially and do not exhibit scaling consistent with the tube model. Definitive plateau-like behaviors are observed in the density–density correlations, normal coordinate decay, and end-to-end vector relaxation of the 192-mer fluids at the highest density. DA - 1996/4/8/ PY - 1996/4/8/ DO - 10.1063/1.471802 VL - 104 IS - 14 SP - 5616-5637 J2 - The Journal of Chemical Physics LA - en OP - SN - 0021-9606 1089-7690 UR - http://dx.doi.org/10.1063/1.471802 DB - Crossref ER - TY - JOUR TI - Propene Oxidation Chemistry in Laminar Premixed Flames AU - Thomas, S.D. AU - Bhargava, A. AU - Westmoreland, P.R. AU - Lindstedt, R.P. AU - Skevis, G. T2 - Bulletin des Sociétés Chimiques Belges DA - 1996/// PY - 1996/// VL - 105 IS - 9 SP - 501–512 ER - TY - JOUR TI - Homogeneous ignition of hydrogen-air mixtures over platinum AU - Bui, P.-A. AU - Vlachos, D.G. AU - Westmoreland, P.R. T2 - Symposium (International) on Combustion AB - The homogeneous ignition of hydrogen-air mixtures over platinum is studied at atmospheric pressure using a stagnation-point flow model with detailed gas-phase kinetics, surface kinetics, and transport phenomena. The momentum, energy, and mass balances are discretized using a second-order finite difference scheme. The obtained set of algebraic equations is then solved using Newton's method. An are-length continuation is employed to determine ignitions and to perform parametric studies. Inhibition of the homogeneous ignition caused by the catalyst is observed in agreement with published experiments. A local maximum in the homogeneous ignition temperature is found at the surface stoichiometric point at ∼15% H2 in air, a composition determined by surface reactions and multicomponent transport effects. The gasphase inhibition is induced mainly by product formation through the termination reaction H+O2+M→HO2+M and by depletion of the fuel below ∼15% H2 in air or of the oxidant above ∼15% H2 in air. Sensitivity analysis shows that desorption of radicals has a minor effect on gas-phase ignition of H2 in air. On the other hand, the dissociative adsorption of O2 through O2+2°→2O°, (° denotes adsorbed species or an adsorption site) has a strong influence on the homogeneous ignition temperature. Reaction path analysis reveals a change in the major surface reaction path for formation of H2O° from 2OH°→H2O°+O° when H2 in air is less than ∼15% to OH°+H°→H2O°+° when this composition is greater than ∼15%. Implications for homogeneous ignition of hydrocarbons near catalysts are also discussed. DA - 1996/1// PY - 1996/1// DO - 10.1016/s0082-0784(96)80402-4 VL - 26 IS - 1 SP - 1763-1770 J2 - Symposium (International) on Combustion LA - en OP - SN - 0082-0784 UR - http://dx.doi.org/10.1016/s0082-0784(96)80402-4 DB - Crossref ER - TY - JOUR TI - Incorporation of Nasal-Lining Mass-Transfer Resistance into a CFD Model for Prediction of Ozone Dosimetry in the Upper Respiratory Tract AU - Cohen Hubal, Elaine A. AU - Kimbell, Julia S. AU - Fedkiw, Peter S. T2 - Inhalation Toxicology AB - AbstractAbstractInhalation of ambient concentrations of ozone (a strong oxidant) has been reported to injure regions of the monkey and rat upper respiratory tract (URT) that contain little intraepithelial mucosubstances (regions lined by transitional epithelium) and to spare adjacent regions that contain abundant stored secretory products (regions lined by respiratory epithelium). It is therefore hypothesized that mucus provides a major resistance to ozone mass transport in the URT. As part of a larger project to predict health risks of inhaled gases, a previously developed, computational fluid dynamics (CFD) model of the Fischer 344 (F344) rat nasal passage was modified to describe transport of ozone. In this study, mass-transfer resistance in the nasal lining was incorporated into the CFD model for prediction of ozone dosimetry. Static mucus and tissue layers were considered. A boundary condition was developed that incorporates mass-transfer resistance in the nasal lining due to one-dimensional diffusion and first-order reaction in the mucus and tissue phases. Physicochemical parameters for ozone were obtained from the literature. Resistance to mass transfer in the submucosal region (blood phase) was neglected due to high tissue-phase reactivity (i.e., the concentration of inhaled chemical in blood was set to zero). To study the possibility that differences in the thickness and/or quality (variation in physico-chemical properties) of mucus coating the transitional and respiratory epithelium account for reported patterns of injury, a simulation was performed into which regional differences in mucus thickness were incorporated. Results suggest that mass-transfer resistance in the mucus phase is important for describing ozone dosimetry in the URT. In addition, mucus thickness may play a role in determining the pattern of ozone-induced nasal lesions. DA - 1996/1// PY - 1996/1// DO - 10.3109/08958379609034267 VL - 8 IS - 9 SP - 831-857 SN - 0895-8378 1091-7691 UR - http://dx.doi.org/10.3109/08958379609034267 ER - TY - JOUR TI - Nitric oxide reduction using platinum electrodes on yttria-stabilized zirconia AU - Walsh, Kenneth J. AU - Fedkiw, Peter S. T2 - Solid State Ionics AB - Abstract A high-temperature, stabilized-zirconia cell with an iridium cathode was used to electrochemically reduce low concentrations of nitric oxide (230–610 ppm) in streams containing oxygen (129–9800 ppm). A combination of thermodynamic considerations, responses to changes in the gas stream, and steady-state galvanostatic experiments suggest that the iridium electrode is converted to iridium dioxide by nitric oxide at open circuit and potentials more positive than −300 mV versus an air electrode. If the electrode is reduced to iridium metal at more negative potentials, nitric oxide can be electrochemically reduced more rapidly than oxygen. DA - 1996/// PY - 1996/// DO - 10.1016/s0167-2738(96)00517-6 VL - 93 IS - 1-2 SP - 17-31 SN - 0167-2738 UR - http://dx.doi.org/10.1016/s0167-2738(96)00517-6 KW - stabilized zirconia KW - nitrogen oxides, platinum electrode KW - ceria KW - electrochemical reduction ER - TY - JOUR TI - Mass-transport models to predict toxicity of inhaled gases in the upper respiratory tract AU - Hubal, E. A. AU - Fedkiw, P. S. AU - Kimbell, J. S. T2 - Journal of Applied Physiology AB - Mass transport (the movement of a chemical species) plays an important role in determining toxic responses of the upper respiratory tract (URT) to inhaled chemicals. Mathematical dosimetry models incorporate physical characteristics of mass transport and are used to predict quantitative uptake (absorption rate) and distribution of inhaled gases and vapors in the respiratory tract. Because knowledge of dose is an essential component of quantitative risk assessment, dosimetry modeling plays an important role in extrapolation of animal study results to humans. A survey of existing mathematical dosimetry models for the URT is presented, limitations of current models are discussed, and adaptations of existing models to produce a generally applicable model are suggested. Reviewed URT dosimetry models are categorized as early, lumped-parameter, and distributed- parameter models. Specific examples of other relevant modeling work are also presented. DA - 1996/4// PY - 1996/4// DO - 10.1152/jappl.1996.80.4.1415 VL - 80 IS - 4 SP - 1415-1427 J2 - Journal of Applied Physiology LA - en OP - SN - 8750-7587 1522-1601 UR - http://dx.doi.org/10.1152/jappl.1996.80.4.1415 DB - Crossref KW - dosimetry models KW - quantitative absorption KW - nasal uptake models ER - TY - JOUR TI - Electrodeposition of high-surface area platinum in a well adherent nafion film on glassy carbon AU - Ye, Jian-Hui AU - Fedkiw, Peter S. T2 - Electrochimica Acta AB - Platinum was electrochemically deposited within a Nafion film coated on glassy carbon (GC) to form a well adherent and high-platinum utilization electrode. Two potential-control procedures were evaluated to form a deposit: a cyclic potential scan and a constant potential, with Pt loadings ranging for each from 60–750 μg Pt cm−2 GC obtained by varying the coulombs discharged. The Pt/Nafion/GC electrodes were annealed at 170 °C before use. Transmission electron microscopy studies revealed that Pt grows as a dispersed, three-dimensional deposit within the film for both techniques. The average particle size for a loading of 60 μg cm−2 is 7.3 nm, which is in good agreement with that (7.1 nm) estimated from electrochemical formation of adsorbed hydrogen. With a Pt loading an order-of-magnitude greater, the particle number density increased, and the observed average particle is larger at 9.8 nm which is smaller than that (19.0 nm) evaluated from electrochemical hydrogen adsorption. The deposit thickness increased with loading and, for a given Pt loading, was less thick when using the steady-potential method; the latter technique, however, yielded a deposit which covered more of the GC-Nafion interface. The mass specific surface area of Pt decreased with loading and ranged from 32-8 m2g−1 as the loading varied from 60–640 μg cm−2. The Pt/Nafion/GC structure is robust in that the electrode can be used to evolve hydrogen or oxygen without damaging the film. In contrast, a Nafion film on smooth Pt is lifted off the surface under similar gas-evolution conditions. DA - 1996/2// PY - 1996/2// DO - 10.1016/0013-4686(95)00314-5 VL - 41 IS - 2 SP - 221-231 J2 - Electrochimica Acta LA - en OP - SN - 0013-4686 UR - http://dx.doi.org/10.1016/0013-4686(95)00314-5 DB - Crossref KW - Nafion KW - platinum KW - glassy carbon KW - electrodeposition ER - TY - JOUR TI - A model for the Kolbe reaction of acetate in a parallel-plate reactor AU - Yan, J. -F. AU - Fedkiw, P. S. AU - Law, C. G., Jr. T2 - Journal of Applied Electrochemistry DA - 1996/2// PY - 1996/2// DO - 10.1007/bf00364068 VL - 26 IS - 2 SP - 175-185 J2 - JOURNAL OF APPLIED ELECTROCHEMISTRY LA - en OP - SN - 0021-891X 1572-8838 UR - http://dx.doi.org/10.1007/bf00364068 DB - Crossref ER - TY - JOUR TI - Effect of the surface expansion and wettability of the capillary on the dynamic surface tension measured by the maximum bubble pressure method AU - Horozov, T.S. AU - Dushkin, C.D. AU - Danov, K.D. AU - Arnaudov, L.N. AU - Velev, O.D. AU - Mehreteab, A. AU - Broze, G. T2 - Colloids and Surfaces A: Physicochemical and Engineering Aspects AB - The dynamic surface tension (DST) of sodium dodecyl sulfate solutions in the presence of sodium chloride is studied by the maximum bubble pressure method. The pressure oscillations are measured with a pressure transducer, while the change of the bubble area with time is determined by means of a video system. The role of the wettability of the capillary is studied by means of measurements with hydrophilic and hydrophobic capillaries. A strong effect of wettability of the capillary on the bubble growth and the DST is observed. The DST data are interpreted with a model for diffusion-controlled adsorption assuming different laws of bubble expansion. The real law of expansion is found to be important for correct interpretation in the case of the hydrophobic capillary. However, the surface expansion is not of primary importance for interpretation of the DST data obtained with the hydrophilic capillary. It is proved that the maximum pressure does not correspond to the hemispherical shape of the bubble in the presence of surfactant. Neglecting this effect does not lead to a significant error in the DST for bubbling periods smaller than several seconds. DA - 1996/// PY - 1996/// DO - 10.1016/0927-7757(96)03574-1 VL - 113 IS - 1-2 SP - 117-126 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030218061&partnerID=MN8TOARS KW - bubble growth KW - dynamic surface tension KW - hydrophilic capillary KW - hydrophobic capillary KW - maximum bubble pressure method KW - surface expansion KW - wettability ER - TY - JOUR TI - Charging of oil-water interfaces due to spontaneous adsorption of hydroxyl ions AU - Marinova, K.G. AU - Alargova, R.G. AU - Denkov, N.D. AU - Velev, O.D. AU - Petsev, D.N. AU - Ivanov, I.B. AU - Borwankar, R.P. T2 - Langmuir DA - 1996/// PY - 1996/// VL - 12 IS - 8 SP - 2045-2051 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0030129467&partnerID=MN8TOARS ER - TY - JOUR TI - Assembly of latex particles by using emulsion droplets as templates. 2. Ball-like and composite aggregates AU - Velev, O.D. AU - Furusawa, K. AU - Nagayama, K. T2 - Langmuir DA - 1996/// PY - 1996/// VL - 12 IS - 10 SP - 2385-2391 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-4244024342&partnerID=MN8TOARS ER - TY - JOUR TI - Assembly of latex particles by using emulsion droplets as templates. 1. Microstructured hollow spheres AU - Velev, O.D. AU - Furusawa, K. AU - Nagayama, K. T2 - Langmuir DA - 1996/// PY - 1996/// VL - 12 IS - 10 SP - 2374-2384 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0000810478&partnerID=MN8TOARS ER - TY - CHAP TI - Mass transfer coefficients for the adsorption of pollutants from aqueous effluents using a pore diffusion model AU - Iturralde, L. AU - Santiso, E. AU - Morales, F. T2 - Chemical industry and environment II A2 - N. Piccinini, A2 - Delorenzo, R. PY - 1996/// VL - 1 PB - Torino: Politecnico di Torino ER - TY - JOUR TI - Biphasic synthesis of phenylacetic and phenylenediacetic acids by interfacial carbonylation of benzyl chloride and dichloro-p-xylene AU - Zhong, YP AU - Godfrey, VM AU - Lim, PK AU - Brown, PA T2 - CHEMICAL ENGINEERING SCIENCE AB - Abstract An organic-water interfacial technique has been successfully extended to the synthesis of phenylacetic and phenylenediacetic acids based on the use of surface-active palladium-(4-dimethylaminophenyl)diphenylphosphine complex in conjunction with dodecyl sodium sulfate to effect the carbonylation of benzyl chloride and dichloro- p -xylene in a toluene-aqueous sodium hydroxide mixture. The product yields at 60°C and 1 atm are essentially quantitative based on the substrate conversions, although carbon monoxide also undergoes a slow hydrolysis reaction along with the carbonylation reactions. The side reaction produces formic acid and is catalyzed by aqueous base but not by palladium. The phosphine ligand is stable to the carbonylation reactions and the palladium can be recovered quantitatively as a compact emulsion between the organic and aqueous phases after the reaction, but the catalytic activity of the recovered palladium is about a third of its initial activity due to product inhibition. The carbonylation of benzyl chloride has an activation energy of 100 kJ/mol, a first-order dependence on the catalyst and substrate concentrations, a zero-order dependence on the carbon monoxide partial pressure, and a variable-order dependence on the aqueous base concentration. A kinetic model is proposed which yields a rate law in accord with the experimental findings. DA - 1996/3// PY - 1996/3// DO - 10.1016/0009-2509(95)00300-2 VL - 51 IS - 5 SP - 757-767 SN - 0009-2509 ER - TY - JOUR TI - Surface enrichment in a miscible polymer blend: An experimental test of self-consistent field and long-wavelength approximation models AU - Genzer, J AU - Faldi, A AU - Oslanec, R AU - Composto, RJ T2 - MACROMOLECULES AB - Neutron reflectivity (NR) and low-energy forward recoil spectrometry (LE-FRES) were used to study surface enrichment in miscible blends of deuterated polystyrene, d-PS, and poly(styrene-co-4-bromostyrene), PBr0.049S, having a 0.049 mole fraction of 4-bromostyrene units. The d-PS component was found to segregate preferentially to the polymer blend/air interface, whereas no enrichment of either component was detected at the polymer blend/silicon interface. The experimental values of the surface concentration, φ1, and the surface excess, z*, of d-PS were interpreted using both the theory of Schmidt and Binder (SB) (J. Phys. II (Paris) 1985, 46, 1631) and the self-consistent field (SCF) approach of Genzer et al. (Phys. Rev. E 1994, 50, 2373). Although both SB and SCF models were found to be in good qualitative agreement with the experimentally measured values of φ1 and z*, we demonstrate that the latter proves to be in better quantitative agreement with the experimental results. Moreover, a comparison of the SB and SCF volume fraction profiles of d-PS revealed that the SCF model described more accurately the experimental profile. We also demonstrated that adding long-range interactions to the surface potential in the SCF model produced just minor changes in the shape of the d-PS profile near the surface. DA - 1996/7/29/ PY - 1996/7/29/ DO - 10.1021/ma951108f VL - 29 IS - 16 SP - 5438-5445 SN - 0024-9297 ER - TY - JOUR TI - Mean-field theory of the interface between a homopolymer and a binary-polymer mixture AU - Genzer, J AU - Faldi, A AU - Composto, RJ T2 - JOURNAL OF CHEMICAL PHYSICS AB - In this paper we investigate the properties of the interface between a homopolymer (A) and a binary polymer mixture (B:C). We have extended the self-consistent field (SCF) model of Helfand [Macromolecules 25, 1676 (1992)] by including the effects of the numbers of segments of polymers on the polymer volume fractions, the interfacial excess of B, zB*, the interfacial tension, γABC, the interfacial width, wABC, and the A–B interfacial overlap, wAB. Other parameters include the polymer interaction parameters, χAB, χAC, and χBC, and the B volume fraction in the B:C mixture, φB∞. As expected, the B component segregates to the A/B:C interface when A–B interactions are more favorable than the A–C ones (χAB&lt;χAC). This interfacial adsorption lowers the interfacial tension and width compared to the pure A/C case, demonstrating the compatibilizing effect of B. As χBC varies from favorable to unfavorable, B segregation is found to increase. Similarly, at constant interaction parameters, B segregation increases as the number of the B segments increases. Furthermore, the addition of a small amount of high molecular weight B to an immiscible A/C blend is found to reduce greatly γABC and thus stabilize the system. Calculations for the case of an athermal mixture B:C with χAB=χAC reveals that the shorter chains are ‘‘entropically driven’’ to the A/B:C interface. DA - 1996/12/8/ PY - 1996/12/8/ DO - 10.1063/1.472936 VL - 105 IS - 22 SP - 10134-10144 SN - 0021-9606 ER - TY - JOUR TI - Removal of organic films from rotating disks using aqueous solutions of nonionic surfactants: Film morphology and cleaning mechanisms AU - Kabin, JA AU - Saez, AE AU - Grant, CS AU - Carbonell, RG T2 - INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH AB - In this work, we consider the cleaning of an organic liquid film, consisting initially of a concentrated solution of abietic acid in isopropyl alcohol, from the surface of a rotating disk by using aqueous solutions of a nonionic surfactant, pentaethylene glycol mono-n-dodecyl ether. The results show that the removal process takes place in three consecutive stages. The first stage is controlled by the solubilization of the abietic acid by surfactant penetration and subsequent mass transfer from the interface to the bulk of the aqueous solution. During the first stage, the film absorbs water from the aqueous solution and breaks up into drops that leave portions of the surface exposed. The absorption of surfactant and water reduces the organic-phase viscosity, until the drops start to move on the disk surface under the action of shear forces. These drops aggregate into spiral-shaped continuous rivulets through which the organic phase flows until it comes off the disk edge. Such behavior occurs during the second stage of cleaning, which has a rate of removal appreciably faster than the first stage. The rivulets are shown to be tangent to the stress exerted by the aqueous solution on the surface of the organic phase. The rivulets eventually break, leading to a third stage with lower removal rates, in which the removal mechanism is apparently the roll up of organic-phase drops under the action of shear forces. In this work, we present experimental evidence that supports the described mechanism, based on photographs showing the morphology of the film structure in the different cleaning stages. A model is derived that relates the empirical observations of cleaning rates to physical parameters describing the solubilizing film hydrodynamics. DA - 1996/12// PY - 1996/12// DO - 10.1021/ie960195c VL - 35 IS - 12 SP - 4494-4506 SN - 0888-5885 ER - TY - JOUR TI - Oxidation of methanol over a palladium monolithic automotive catalyst AU - Frankel, KA AU - Mew, TM AU - Lim, PK AU - Roberts, GW T2 - ENVIRONMENTAL SCIENCE & TECHNOLOGY AB - The oxidation of methanol and its partial oxidation products, carbon monoxide and formaldehyde, were studied using a monolithic catalyst containing palladium. Experimental conditions simulated those in the catalytic converter of a methanol-fueled automobile. With a properly activated catalyst and a fuel-lean feed, carbon dioxide was the only carbon-containing product, and the methanol conversion above the light-off temperature of the catalyst appeared to be controlled by mass transfer from the bulk gas stream to the surface of the monolith. Under fuel-rich conditions, carbon monoxide and formaldehyde were formed along with carbon dioxide. The highest formaldehyde yield, about 4% of the methanol reacted, occurred at a relatively low feed temperature, about 350 K, essentially the light-off temperature of the catalyst. The formaldehyde yield decreased as the feed temperature increased and was essentially zero above about 600 K. When a thermally-deactivated catalyst was used, the formaldehyde yield increased significantly and formaldehyde was observed over a wider range of feed temperatures and under fuel-lean conditions. With the properly activated catalyst, multiple steady states were observed in the form of a reaction hysteresis with respect to feed temperature. DA - 1996/6// PY - 1996/6// DO - 10.1021/es950760n VL - 30 IS - 6 SP - 1997-2003 SN - 0013-936X ER - TY - JOUR TI - Effect of molecular architecture on DBS-induced block copolymer gels: A rheological study AU - Nunez, CM AU - Whitfield, JK AU - Mercurio, DJ AU - Ilzhoefer, , JR AU - Spontak, RJ AU - Khan, SA T2 - MACROMOLECULAR SYMPOSIA AB - Abstract Dibenzylidene sorbitol (DBS) is capable of gelling a variety of organic solvents and polymeric materials by forming a rigid, 3‐D hydrogen‐bonded network. In this work, two poly(siloxane)/poly(propylene oxide) segmented copolymers of equal composition and molecular weight, but different architectures (endblocked vs. pendant), as well as a pure poly(propylene oxide), have been gelled with DBS. We have investigated the dynamic rheological properties of these gels to ascertain the effect of copolymer architecture, PDMS comonomer and DBS concentration on network formation. DA - 1996/4// PY - 1996/4// DO - 10.1002/masy.19961060126 VL - 106 SP - 275-286 SN - 1022-1360 ER - TY - JOUR TI - Dynamic and equilibrium phase behavior in the C(12)E(5) abietic acid H2O system AU - Beaudoin, SP AU - Carbonell, RG AU - Grant, CS T2 - JOURNAL OF COLLOID AND INTERFACE SCIENCE AB - Previous research has investigated the removal of representative flux residues (abietic acid (AA) in isopropyl alcohol (IPA)) from printed wiring assemblies using aqueous solutions of a nonionic surfactant (pentaethylene glycol mono-n-dodecyl ether (C12E5)). To optimize cleaning with this surfactant, greater understanding of the equilibrium and dynamic phase behavior in the AA-C12E5-H2O system is required. In this research, partial ternary phase diagrams were developed at 60 and 45°C (above the binary cloud point). Increasing the AA content of the system caused isotropic surfactant (L2) and lamellar liquid crystalline (La) phases to form at lower temperatures than in the binary C12E5–H2O system. As the temperature increased, the solubility of AA in the L2 phase increased considerably, while the AA content of the La phase was not affected as strongly. The dynamic phase behavior resulting from contact of micellar C12E5solutions with AA or AA/IPA particles at 24°C (below the binary cloud point) and 45°C was also observed. When AA or AA/IPA particles were contacted with 4.1 × 10−3MC12E5solutions, the surfactant and water penetrated into the particles to create isotropic liquid aggregates. When particles were contacted with more concentrated micellar C12E5solutions (0.25M), a new concentrated surfactant phase surrounded the particles and solubilized the AA. DA - 1996/9/25/ PY - 1996/9/25/ DO - 10.1006/jcis.1996.0489 VL - 182 IS - 2 SP - 465-472 SN - 0021-9797 KW - micelles KW - nonionic surfactants KW - surfactant phase behavior KW - detergency KW - solubilization ER - TY - JOUR TI - Cryo-electron microscopy of polymer particles in a high cell density synthetic biofilm AU - Thiagarajan, V. AU - Ming, Y. AU - Scriven, L. E. AU - Flickinger, M. C. T2 - Progress in Biotechnology DA - 1996/// PY - 1996/// VL - 11 IS - Immobilized Cells SP - 298-303 ER - TY - JOUR TI - Controlled black liquor viscosity reduction through salting-in AU - Roberts, JE AU - Khan, SA AU - Spontak, RJ T2 - AICHE JOURNAL AB - Abstract Black liquor viscosity increases exponentially with solids content and therefore causes processing problems for the paper industry by being a limiting factor in the Kraft pulp process. This study investigates a new approach for achieving viscosity reduction by “salting‐in” black liquor through the addition of thiocyanate salts. These salts generally increase the solubility of the polymer constituents in black liquor, leading to a decrease in its viscosity. Several thiocyanate salts capable of reducing liquor viscosity by more than two orders of magnitude have been identified, with viscosity reduction greatest at high solids content. Salting‐in of black liquor depends on the cation paired with the thiocyanate anion, as well as on solution pH and temperature. Comparative studies reveal that GuSCN is the most effective viscosity‐reducing agent of the series examined and that lignin plays an important role in the viscosity behavior of both unmodified and salted‐in black liquor at high solids concentrations. These experimental findings are interpreted in terms of the underlying principles that describe salting‐in and how it affects aqueous solution structure. DA - 1996/8// PY - 1996/8// DO - 10.1002/aic.690420821 VL - 42 IS - 8 SP - 2319-2326 SN - 0001-1541 ER - TY - JOUR TI - A novel approach to black liquor viscosity reduction using salt additives AU - Roberts, J.E. AU - Spontak, R.J. AU - Jameel, H. AU - Khan, S.A. T2 - TAPPI Journal DA - 1996/// PY - 1996/// VL - 79 IS - 8 SP - 167-174 ER - TY - JOUR TI - MBMS analysis of a fuel-lean ethylene flame AU - Bhargava, A. AU - Westmoreland, P. R. T2 - Chemical and Physical Processes in Combustion DA - 1996/// PY - 1996/// SP - 421-424 ER - TY - JOUR TI - Initial measurements from reacting flows of hydrocarbons with chlorine AU - Oulundsen, G. E. AU - Westmoreland, P. R. T2 - Chemical and Physical Processes in Combustion DA - 1996/// PY - 1996/// SP - 345-348 ER - TY - JOUR TI - Dynamic rate and thickness metrology during poly-Si rapid thermal chemical vapor deposition from SiH4 using real time in situ mass spectrometry AU - Tedder, LL AU - Rubloff, GW AU - Cohaghan, BF AU - Parsons, Gregory T2 - Journal of Vacuum Science & Technology a-Vacuum Surfaces and Films AB - Real-time in situ mass spectrometry has been applied to poly-Si rapid thermal chemical vapor deposition (RTCVD) (from SiH4) on thermally grown SiO2 as a way to determine film thickness at the end of the process and to infer dynamic deposition rate during the process for run-to-run and real-time control applications. Monitoring process ambient at 5 Torr is achieved using two-stage differential pumping of a sampling aperture in the exhaust stream, and a rapid response time (∼1 s for a ∼30 s process cycle) allows for real time sensing of reactant input, product generation, and reactant depletion. Active mass spectrometric sampling of the reaction by-product (H2 generated by SiH4 decomposition) provides a monitor of the total reaction/deposition rate during poly-Si RTCVD in the range 550–850°C. Product generation as a function of temperature is readily distinguished from reactant cracking fragments by spectral analysis. A well-defined monotonic correlation between the time-integrated H+2 product signal and the poly-Si film thickness, determined ex situ by single-point interferometry (Nanometrics), demonstrates that the integrated mass spectrometric signal can provide real-time thickness metrology. In addition, the time-dependence of product and reactant signals provides a real-time indication of detailed equipment behavior during the process. DA - 1996/// PY - 1996/// DO - 10.1116/1.579887 VL - 14 IS - 2 SP - 267-270 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1996UA57500001&KeyUID=WOS:A1996UA57500001 ER - TY - JOUR TI - Ab initio calculation of hydrogen abstraction energetics from silicon hydrides AU - Srinivasan, E AU - Yang, H AU - Parsons, GN T2 - JOURNAL OF CHEMICAL PHYSICS AB - In this article, we present calculated energies for the abstraction of hydrogen from silicon monohydride and silicon dihydride surface bonding units by atomic hydrogen obtained using ab initio configuration interaction theory. Three and four silicon atom clusters are used to model the dihydride and monohydride units, respectively. Heats of reaction and activation energy barriers are calculated, including the vibrational energies of the initial, final, and transition states. Hydrogen abstraction from a Si–H unit (H+Si4H10→Si4H9+H2) is found to be exothermic by 9.4 kcal/mol with a transition state energy barrier of 5.5 kcal/mol when H approaches along the surface normal. The dihydride abstraction reaction, H+Si3H8→Si3H7+H2, is exothermic by 7.7 kcal/mol and has an energy barrier of 7.3 kcal/mol when H is approaching along Si–H axis. The barrier is larger for hydrogen atom approaching along the surface normal. The larger barrier for abstraction from a dihydride unit is consistent with our experimental observation of a preferential reduction in monohydride bond concentrations when hydrogenated silicon films are exposed to atomic hydrogen during plasma deposition. DA - 1996/10/1/ PY - 1996/10/1/ DO - 10.1063/1.472387 VL - 105 IS - 13 SP - 5467-5471 SN - 0021-9606 UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:A1996VL46900020&KeyUID=WOS:A1996VL46900020 ER - TY - JOUR TI - The effect of reversibility on the selectivity of parallel reactions in a porous catalyst AU - Roberts, GW AU - Lamb, HH T2 - CHEMICAL ENGINEERING SCIENCE AB - The selectivity of two first-order, parallel reactions, one reversible and one irreversible, can be altered substantially by the presence of an intraparticle diffusion resistance. At very large resistances, the relative selectivity approaches an asymptotic limit which depends on the kinetic, transport and thermodynamic parameters of the reaction system. It is possible for the selectivity to the product of the reversible reaction to change sign as the pore diffusion resistance increases, i.e. there can be a net formation of that product at low resistances and a net consumption at high resistances. In some cases, the rate of consumption of the product of the reversible reaction can be so high that the ratio of product concentration to reactant concentration in the bulk fluid moves away from the equilibrium ratio. This behavior contrasts markedly with that of two irreversible, first-order reactions in parallel, where the selectivity is independent of the intraparticle diffusion resistance. DA - 1996/2// PY - 1996/2// DO - 10.1016/0009-2509(95)00266-9 VL - 51 IS - 3 SP - 441-448 SN - 0009-2509 ER - TY - PAT TI - Production of Amino Acids Using Methylotrophic Bacillus AU - Hanson, R.S. AU - Flickinger, M.C. AU - Schendel, F.J. AU - Guettler, M.V. C2 - 1996/// DA - 1996/// PY - 1996/// ER - TY - JOUR TI - Pd/silica cluster catalysts: Synthesis and reactivity with H-2 and C2H4 AU - Reifsnyder, SN AU - Lamb, HH T2 - CATALYSIS LETTERS DA - 1996/// PY - 1996/// DO - 10.1007/bf00815276 VL - 40 IS - 3-4 SP - 155-161 SN - 1011-372X KW - palladium catalysts KW - metal clusters KW - EXAFS spectroscopy KW - hydride KW - carbide ER - TY - JOUR TI - BAC-MP4 predictions of thermochemical data for C-1 and C-2 stable and radical hydrofluorocarbons and oxidized hydrofluorocarbons AU - Zachariah, M. R. AU - Westmoreland, Phillip AU - Burgess, D. R. F. AU - Tsang, W. AU - Melius, C. F. T2 - JOURNAL OF PHYSICAL CHEMISTRY AB - An ab initio bond additivity corrected quantum chemistry procedure has been applied to the development of a data base for thermochemistry of C/H/F/O species. This information has been used to construct a chemical kinetic mechanism for the prediction of the behavior of fluorocarbons as flame suppressants, with clear applications to plasma and atmospheric chemistry as well. Bond additivity corrected (BAC) Moller−Plesset fourth-order perturbation theory (MP4) calculations have been performed to obtain a large body of thermochemical data on about 100 closed and open shelled fluorocarbon species. For about 70 of these species, literature values for enthalpies of formation were available for comparison to the calculated values. The average difference between the calculated and literature values was about 9 kJ/mol. The results indicate that the BAC-MP4 procedure can provide energies that are comparable in accuracy to most experimentally derived values, at lower computational costs relative to other more computationally expensive ab initio molecular orbital methods. This work provides a substantial data base of thermochemical data for fluorinated hydrocarbons constructed in a self-consistent manner. DA - 1996/5/23/ PY - 1996/5/23/ DO - 10.1021/jp952467f VL - 100 IS - 21 SP - 8737-8747 SN - 0022-3654 ER -