@article{english_laurer_spontak_khan_2002, title={Hydrophobically modified associative polymer solutions: Rheology and microstructure in the presence of nonionic surfactants}, volume={41}, ISSN={["0888-5885"]}, DOI={10.1021/ie020409s}, abstractNote={We report on the rheology and morphology of a hydrophobically modified alkali-swellable emulsion (HASE) polymer solubilized in alkaline media containing nonionic surfactants. The HASE polymer consists of complex alkylaryl hydrophobes composed of oligomeric nonylphenol condensates attached to a poly(ethyl acrylate-co-methacrylic acid) backbone. The complex linear viscoelastic response of the polymer in alkaline solution suggests an unentangled network with an appreciable fraction of microgel. The concentration and hydrophile−lipophile balance (HLB) of nonionic surfactants profoundly affect the solution rheology. A surfactant of high HLB inhibits the dynamic network connectivity of the HASE polymer, as demonstrated by reductions of both the steady-shear viscosity and the dynamic storage modulus. The shear-induced structuring previously reported for this polymer is also progressively diminished as the surfactant concentration is increased. In contrast, the addition of a low-HLB surfactant promotes system structuring, as evidenced by (i) increases in the shear viscosity and the high-frequency plateau modulus and (ii) retention of the ability to undergo shear-induced structuring. We also employ cryofracture-replication transmission electron microscopy for the first time with regard to HASE associative polymers to examine the morphological characteristics of selected systems. The morphology of the HASE polymer in both latex and solubilized form appears more complex than previously anticipated, and a reasonable interpretation of these new data is provided.}, number={25}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={English, RJ and Laurer, JH and Spontak, RJ and Khan, SA}, year={2002}, month={Dec}, pages={6425–6435} }
 @article{laurer_khan_spontak_satkowski_grothaus_smith_lin_1999, title={Morphology and rheology of SIS and SEPS triblock copolymers in the presence of a midblock-selective solvent}, volume={15}, ISSN={["0743-7463"]}, DOI={10.1021/la981441n}, abstractNote={While numerous fundamental studies have sought to elucidate the effect of a parent homopolymer on the morphological characteristics and mechanical properties of microphase-ordered block copolymer blends, few comparable efforts have extended such studies to concentrated copolymer solutions in the presence of a low-molar-mass block-selective solvent. In this work, we investigate the microstructures that form in blends of a poly(styrene-block-isoprene-block-styrene) (SIS) triblock copolymer with a midblock-selective aliphatic mineral oil. To discern the influence of midblock/oil compatibility on blend morphology and properties, identical blends with a poly[styrene-block-(ethylene-alt-propylene)-block-styrene] (SEPS) copolymer, the hydrogenated variant of the SIS copolymer, have likewise been examined. The saturated midblock of the SEPS copolymer is responsible for the observed shifts in morphology stability limits and higher dynamic elastic shear moduli relative to the SIS analogue. These results reveal that...}, number={23}, journal={LANGMUIR}, author={Laurer, JH and Khan, SA and Spontak, RJ and Satkowski, MM and Grothaus, JT and Smith, SD and Lin, JS}, year={1999}, month={Nov}, pages={7947–7955} }
 @article{laurer_spontak_1999, title={P-chlorostyrene}, journal={Polymer data handbook}, publisher={New York: Oxford University Press}, author={Laurer, J. H. and Spontak, R. J.}, year={1999}, pages={380–386} }
 @article{laurer_hajduk_dreckotter_smith_spontak_1998, title={Bicontinuous morphologies in homologous multiblock copolymers and their homopolymer blends}, volume={31}, ISSN={["0024-9297"]}, DOI={10.1021/ma9807872}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTBicontinuous Morphologies in Homologous Multiblock Copolymers and Their Homopolymer BlendsJonathan H. Laurer, Damian A. Hajduk, Stefan Dreckötter, Steven D. Smith, and Richard J. SpontakView Author Information Departments of Materials Science & Engineering and Chemical Engineering, North Carolina State University, Raleigh, North Carolina 27695, Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, and Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239 Cite this: Macromolecules 1998, 31, 21, 7546–7549Publication Date (Web):October 2, 1998Publication History Received18 May 1998Revised17 August 1998Published online2 October 1998Published inissue 1 October 1998https://doi.org/10.1021/ma9807872Copyright © 1998 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views229Altmetric-Citations13LEARN 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 (140 KB) Get e-AlertsSUBJECTS:Conformation,Copolymers,Homopolymers,Morphology,X-ray scattering Get e-Alerts}, number={21}, journal={MACROMOLECULES}, author={Laurer, JH and Hajduk, DK and Dreckotter, S and Smith, SD and Spontak, RJ}, year={1998}, month={Oct}, pages={7546–7549} }
 @article{laurer_smith_samseth_mortensen_spontak_1998, title={Interfacial modification as a route to novel bilayered morphologies in binary block copolymer/homopolymer blends}, volume={31}, ISSN={["1520-5835"]}, DOI={10.1021/ma980200j}, abstractNote={Addition of a relatively low-molecular-weight parent homopolymer to a lamellar AB diblock copolymer constitutes a reliable means by which to induce, in controllable fashion, transitions to other morphologies. In this study, we examine the effect of interfacial modification on such transitions in "extended" A(A/B)B copolymer/homopolymer blends in which (i) the A/B midblock fraction (relative to the copolymer molecular weight) is varied from 0.0 to 0.4 in 0.1 increments and (ii) the overall concentration of A ranges from 0.50 to 0.95. As this A/B fraction is increased at constant blend composition, the extent of homopolymer-induced lamellar swelling becomes measurably less pronounced, indicating that the A/B midblock serves to delocalize repulsion along the interphase separating adjacent lamellae. At higher homopolymer concentrations, an increase in the A/B fraction results in the formation of either unilamellar vesicles or a randomly connected bilayered membrane, rather than micelles. These membranes become unstable and transform to micelles at high copolymer dilution. The results presented here are discussed in terms of the complex morphologies observed in, and predicted for, low-molar-mass (co)surfactant systems.}, number={15}, journal={MACROMOLECULES}, author={Laurer, JH and Smith, SD and Samseth, J and Mortensen, K and Spontak, RJ}, year={1998}, month={Jul}, pages={4975–4985} }
 @article{hong_laurer_zielinski_samseth_smith_duda_spontak_1998, title={Morphological and isothermal diffusive probe analyses of low-molecular-weight diblock copolymers}, volume={31}, ISSN={["0024-9297"]}, DOI={10.1021/ma971516e}, abstractNote={While numerous scattering and rheological studies have investigated the disordering mechanism of low-molecular-weight poly(styrene-b-isoprene) (SI) diblock copolymers, relatively few efforts have addressed the real-space morphologies and transport properties of such copolymers at conditions near the order−disorder transition (ODT). In this work, the morphological features of seven compositionally symmetric (50/50 w/w S/I) copolymers ranging in molecular weight from 5000 to 20000, as well as several of their blends, are examined by transmission electron microscopy and small-angle neutron scattering. These results are used to interpret toluene gravimetric sorption data collected at various temperatures. At temperatures above the styrenic glass transition temperature, microphase-ordered copolymer melts are found to exhibit Fickian diffusion. In the case of a copolymer with an experimentally accessible ODT, anomalous sorption (as evidenced by equilibrium overshoot in gravimetric mass-uptake curves) is observe...}, number={7}, journal={MACROMOLECULES}, author={Hong, SU and Laurer, JH and Zielinski, JM and Samseth, J and Smith, SD and Duda, JL and Spontak, RJ}, year={1998}, month={Apr}, pages={2174–2184} }
 @article{laurer_mulling_khan_spontak_bukovnik_1998, title={Thermoplastic elastomer gels. I. Effects of composition and processing on morphology and gel behavior}, volume={36}, DOI={10.1002/(sici)1099-0488(19980930)36:13<2379::aid-polb13>3.3.co;2-7}, abstractNote={Thermoplastic elastomer gels (TPEGs) composed of a poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer and a low-volatility, midblock-compatible mineral oil have been investigated at different oil concentrations to ascertain the effect of composition on TPEG morphology and mechanical properties. The impact of thermal processing is also examined by comparing gels thermally quenched to 0°C or slowly cooled to ambient temperature. Transmission electron micrographs reveal that gels with 70 to 90 wt % oil exhibit styrenic micelles measuring ca. 24 nm in diameter. Variation in composition or cooling rate does not have any perceivable effect on micelle size or shape, whereas the rate at which the gels are cooled influences the extent of microstructural order and the time to rupture (tR) at constant strain. Dynamic rheological testing confirms the presence of a physically crosslinked network at TPEG compositions ranging from 70 to 90 wt % oil, independent of cooling rate. Results presented here suggest that the dynamic elastic shear modulus (G′) scales as tαR where α varies from 0.41 to 0.59, depending on cooling rate. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2379–2391, 1998}, number={13}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Laurer, J. H. and Mulling, J. F. and Khan, Saad and Spontak, Richard and Bukovnik, R.}, year={1998}, pages={2379–2391} }
 @article{laurer_mulling_khan_spontak_lin_bukovnik_1998, title={Thermoplastic elastomer gels. II. Effects of composition and temperature on morphology and gel rheology}, volume={36}, DOI={10.1002/(sici)1099-0488(199810)36:14<2513::aid-polb5>3.3.co;2-6}, number={14}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Laurer, J. H. and Mulling, J. F. and Khan, Saad and Spontak, Richard and Lin, J. S. and Bukovnik, R.}, year={1998}, pages={2513–2523} }
 @article{laurer_ashraf_smith_spontak_1997, title={Complex phase behavior of a disordered ''random'' diblock copolymer in the presence of a parent homopolymer}, volume={13}, ISSN={["0743-7463"]}, DOI={10.1021/la960807y}, abstractNote={Previous efforts addressing binary blends of a block copolymer and a parent homopolymer have principally employed ordered copolymers in either the intermediate- or strong-segregation regimes. In this work, blends composed of a disordered (75/25)-b-(50/50) poly[(styrene-r-isoprene)‘-b-(styrene-r-isoprene)‘‘] (S/I)‘-b-(S/I)‘‘ random diblock copolymer (RBC) and homopolystyrene (hS) have been investigated. Blend morphologies, characterized by transmission electron microscopy, are correlated with hS concentration and molecular weight, as well as with changes in the hS Tg, as measured by thermal calorimetry. At low hS fractions (up to 20 wt % hS), the S/I block sequences in the RBC induce competition between attractive and repulsive interactions with hS molecules, resulting in the formation of thin hS channel structures in a continuous RBC matrix. An increase in hS concentration or molecular weight serves to broaden the channels until the morphology resembles macrophase-separated hS domains containing micelle-l...}, number={8}, journal={LANGMUIR}, author={Laurer, JH and Ashraf, A and Smith, SD and Spontak, RJ}, year={1997}, month={Apr}, pages={2250–2258} }
 @article{laurer_fung_sedat_smith_samseth_mortensen_agard_spontak_1997, title={From micelles to randomly connected, bilayered membranes in dilute block copolymer blends}, volume={13}, ISSN={["0743-7463"]}, DOI={10.1021/la9608876}, abstractNote={As macromolecular surfactants, diblock copolymers order into a variety of morphologies in the presence of a parent homopolymer. Here, we probe the effects of chemical incompatibility and interfacial rigidity on the morphology of copolymer/homopolymer blends at constant blend composition. Five copolymers, each possessing a random-sequence midblock that is varied from 0 to 40 wt % of the copolymer molecular weight, have been synthesized for this purpose. While copolymer micelles are representative of dilute (homopolymer-rich) blends, complex bilayered morphologies, including vesicles and the anomalous isotropic `sponge` phase, are produced upon increasing the midblock fraction. Small-angle neutron scattering provides a quantitative assessment of characteristic microstructural dimensions, while transmission electron microtomography yields the first three-dimensional images of the randomly connected, bilayered membrane comprising the sponge phase. 31 refs., 3 figs.}, number={8}, journal={LANGMUIR}, author={Laurer, JH and Fung, JC and Sedat, JW and Smith, SD and Samseth, J and Mortensen, K and Agard, DA and Spontak, RJ}, year={1997}, month={Apr}, pages={2177–2180} }
 @article{laurer_ashraf_smith_samseth_spontak_1997, title={Macromolecular self-assembly in dilute sequence-controlled block copolymer/homopolymer blends}, volume={4}, ISSN={["0968-5677"]}, DOI={10.1016/S0968-5677(96)00048-X}, abstractNote={Conventional block copolymers consist of two long contiguous monomer sequences (‘blocks’) that can, in the same fashion as low-molar-mass surfactants, self-assemble into various microstructural elements (e.g., micelles at low copolymer concentrations) to minimize repulsive contacts in the presence of a parent homopolymer. In this work, we explore the existence of segment-specific interactions, as well as the possibility of tailoring these blend morphologies (and producing altogether new ones), with novel sequence-controlled block copolymers. These copolymers are comprised of at least one block that is a random segment composed of both constituent monomer species. Transmission electron microscopy is employed here to examine the bilayered membranes and channel structures that form in two different series of such copolymers in dilute copolymer/homopolymer blends.}, number={1-2}, journal={SUPRAMOLECULAR SCIENCE}, author={Laurer, JH and Ashraf, A and Smith, SD and Samseth, J and Spontak, RJ}, year={1997}, pages={121–126} }
 @article{laurer_hajduk_fung_sedat_smith_gruner_agard_spontak_1997, title={Microstructural analysis of a cubic bicontinuous morphology in a neat SIS triblock copolymer}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma970449l}, abstractNote={Department of Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695, Department of Physics, Princeton University, Princeton, New Jersey 08544, Graduate Group in Biophysics, University of California, San Francisco, California 94143, Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143, Corporate Research Division, The Procter & Gamble Company, Cincinnati, Ohio 45239, and Howard Hughes Medical Institute, University of California, San Francisco, California 94143}, number={13}, journal={MACROMOLECULES}, author={Laurer, JH and Hajduk, DA and Fung, JC and Sedat, JW and Smith, SD and Gruner, SM and Agard, DA and Spontak, RJ}, year={1997}, month={Jun}, pages={3938–3941} }
 @inproceedings{laurer_mulling_bukovnik_spontak_1997, title={Phase behavior of triblock copolymers upon incorporation of nonparent, midblock-associating additives}, volume={461}, DOI={10.1557/proc-461-69}, abstractNote={ABSTRACT}, booktitle={Morphological control in multiphase polymer mixtures: Symposium held December 2-5, 1996, Boston, Massachusetts, U.S.A. 1997 (Materials Research Society symposium proceedings)}, publisher={Warrendale, PA: Materials Research Society}, author={Laurer, J. H. and Mulling, J. F. and Bukovnik, R. and Spontak, Richard}, editor={R. M. Briber, C. C. Han and Peiffer, D. G.Editors}, year={1997}, pages={69–74} }
 @article{smith_laurer_ade_smith_ashraf_spontak_1997, title={X-ray microscopy and NEXAFS spectroscopy of macrophase-separated random block copolymer/homopolymer blends}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma9612687}, abstractNote={Morphological characterization of bulk polymer blends or compatibilized alloys at submicron spatial resolution has almost exclusively relied upon electron microscopy techniques. Since, however, most organic polymers are composed of carbon and light elements, an arsenal of methods to enhance phase contrast has been developed to facilitate discrimination and analysis of propertygoverning morphological features.1 For transmission electron microscopy (TEM), chemical modification of polymeric specimens through, for example, functionality-specific incorporation of heavy-metal staining agents (typically OsO4 or RuO4) may result in ambiguous results due to an inadequate understanding of the staining reaction or competing reaction kinetics. While microanalytical techniques such as light-element energydispersive X-ray mapping2 and electron spectroscopic (energy-filtered) imaging3-5 can potentially eliminate the need for chemical modification in TEM and have proven highly valuable in identifying morphological characteristics in unmodified multiphase polymer systems, they are typically only capable of distinguishing among constituent elements. In addition, appropriate steps must be exercised during data acquisition to minimize specimen damage due to electron beam irradiation. Another microscopy technique recently applied to the morphological characterization of multiphase polymers is X-ray microscopy (XRM),6-9 in which chemical sensitivity is based on the principles of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.10 This technique utilizes a diffractive optical element (zone plate) to focus highly monochromatic soft X-rays in the energy range of 200-600 eV generated by a synchrotron radiation source onto an ultrathin polymer specimen (typically 100-200 nm in thickness). The transmitted flux is detected as a function of specimen position as the specimen is raster-scanned by piezoelectric transducers. A detailed description of the microscope employed in this work is provided elsewhere.11 The practical spatial resolution of XRM is dictated by zone plate technology, with the smallest available probe presently limited to a full width at half-maximum of about 55 nm, resulting in a minimum feature resolution of about 35 nm. Recent XRM studies of multiphase polymers have successfully elucidated the morphological characteristics of a binary blend composed of polypropylene (PP) and poly(styrene-r-acrylonitrile) (SAN).6,8 Such blends are expected a priori to be highly demixed due to the chemical dissimilarity of the constituent polymers. Moreover, SAN (unlike PP) contains nitrogen, in which case the SAN spatial distribution can be discerned by either XRM or the element-specific techniques mentioned earlier. In this work, we explore the sensitivity of XRM by examining a polymer blend in which the constituent materials are identical in terms of the elements present (C and H only) and, moreover, differ only in terms of their fraction of the same chemical moiety (polystyrene, PS). As a consequence, blends of this type have been found12,13 to exhibit complex phase behavior that is highly dependent on both blend composition and molecular weight considerations. Results obtained here from XRM are compared with TEM micrographs of the same blend after functionalityspecific OsO4 staining. The polymers employed in this work were PS with Mh n ) 120 000 andMh w/Mh n≈ 1.04 and a “random” diblock copolymer (RBC) synthesized by living anionic polymerization in the presence of sec-butyllithium and a potassium alkoxide. A detailed description of the copolymer synthesis and molecular characterization (in terms of monomer sequencing) is provided elsewhere14-16 and is not addressed, for the sake of brevity, in this communication. The RBC was a poly[(styrene-r-isoprene)′-b-(styrene-r-isoprene)′′], (S/I)′-b-(S/I)′′, copolymer, where the ′ and ′′ denote different block compositions, namely, 75/25 and 50/50 (wt %) S/I. The overall composition of the RBC was 68 wt % S, as measured by 1H NMR, and the block lengths were approximately 40 000 each. Two RBC/PS blends, one consisting of 20 wt % RBC and 80 wt % PS and the other 80 wt % RBC and 20 wt % PS, were prepared by solution casting from toluene, as described elsewhere.13 Upon slow solvent evaporation and subsequent annealing, the resultant films were sectioned in a Reichert-Jung Ultracut-S cryoultramicrotome maintained at -100 °C. Sections for TEM analysis, nominally 100-120 nm in thickness and stained with the vapor of OsO4(aq) for 90 min, were imaged on a Zeiss EM902 electron spectroscopic microscope operated at 80 kV and ∆E ) 50 eV. The XRM analysis was performed on the X-1A Beamline of the National Synchrotron Light Source at Brookhaven National Laboratory.}, number={3}, journal={MACROMOLECULES}, author={Smith, AP and Laurer, JH and Ade, HW and Smith, SD and Ashraf, A and Spontak, RJ}, year={1997}, month={Feb}, pages={663–666} }