@misc{walker_frankowski_spontak_2008, title={Thermodynamics and kinetic processes of polymer blends and block copolymers in the presence of pressurized carbon dioxide}, volume={20}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200700076}, abstractNote={AbstractEnvironmentally‐responsible materials processing is becoming an important global consideration in a wide variety of technologies, especially those wherein volatile and/or residual organic solvents cannot be tolerated. In this context, polymer processing has benefited tremendously from advances achieved using high‐pressure CO2 as a viscosity modifier, plasticizing agent, foaming agent, and reaction medium. Pressurized CO2 is environmentally benign, inexpensive, sustainable, and versatile owing to its gas‐like viscosity and liquid‐like solubility, which can be tuned through judicious choice of temperature and pressure. The addition of high‐pressure CO2 to homopolymer blends and block copolymers can have a profound impact on polymer thermodynamics and kinetic processes since the number of interacting species increases. As a result, the compressibility as well as plasticization and intermolecular screening effects become non‐negligible. In this work, we review how these factors influence such polymeric systems, and discuss commercial polymer processes and applications that benefit from the use of high‐pressure CO2.}, number={5}, journal={ADVANCED MATERIALS}, author={Walker, Teri A. and Frankowski, David J. and Spontak, Richard J.}, year={2008}, month={Mar}, pages={879–898} }
 @misc{desimone_khan_royer_spontak_walker_gay_siripurapu_2004, title={Methods of making foamed materials of blended thermoplastic polymers using carbon dioxide}, volume={6,790,870}, number={2004 Sept. 14}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={DeSimone, J. M. and Khan, S. A. and Royer, J. R. and Spontak, R. J. and Walker, T. A. and Gay, Y. J. and Siripurapu, S.}, year={2004} }
 @article{walker_colina_gubbins_spontak_2004, title={Thermodynamics of poly(dimethylsiloxane)/poly(ethylmethylsiloxane) (PDMS/PEMS) blends in the presence of high-pressure CO2}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma034920o}, abstractNote={Processing polymer blends in the presence of high-pressure carbon dioxide (CO2) affords numerous advantages over organic solvents and is becoming a commercially viable and environmentally responsible alternative in the development of new multicomponent materials. A prerequisite to such processing is a fundamental understanding of how high-pressure CO2 influences the phase behavior of polymer blends. In this work, we use high-pressure spectrophotometry to measure the cloud point (Tcp) of poly(dimethylsiloxane)/poly(ethylmethylsiloxane) (PDMS/PEMS) blends as a function of CO2 pressure (P) in the vapor phase. Results obtained here at different blend compositions indicate that values of Tcp for this upper critical solution temperature (UCST) blend (i) generally increase with increasing pressure and (ii) collapse onto a master curve of ΔTcp(P) for pressures up to about 35 MPa. These data are analyzed by the Sanchez−Lacombe equation of state to ascertain the temperature dependence of an effective interaction pa...}, number={7}, journal={MACROMOLECULES}, author={Walker, TA and Colina, CM and Gubbins, KE and Spontak, RJ}, year={2004}, month={Apr}, pages={2588–2595} }
 @article{walker_melnichenko_wignall_lin_spontak_2003, title={Phase behavior of poly(methyl methacrylate)/poly(vinylidene fluoride) blends in the presence of high-pressure carbon dioxide}, volume={204}, ISSN={["1521-3935"]}, DOI={10.1002/macp.200350075}, abstractNote={AbstractPrevious efforts have demonstrated that high‐pressure CO2 can markedly influence the phase behavior of amorphous polymer blends. In this work, we examine the effect of high‐pressure CO2 on the miscibility of blends composed of glassy poly(methyl methacrylate) (PMMA) and semicrystalline poly(vinylidene fluoride) (PVDF). Blends of this type are known to exhibit lower critical solution temperature (LCST) behavior with partial miscibility up to ≈50–60 wt.‐% PVDF at ambient conditions. Two miscible PMMA/PVDF blends have been systematically exposed to high‐pressure CO2 at 35 °C and pressures below and above the critical pressure. Small‐angle X‐ray scattering reveals that the scattering intensity at high scattering angles shows little dependence on pressure at low CO2 pressures, but increases substantially at relatively high CO2 pressures. Transmission electron microscopy and differential scanning calorimetry analyses confirm that the blends are initially quasi‐homogeneous with diffuse PVDF‐rich dispersions and a single glass transition temperature. After exposure to relatively high CO2 pressures, however, the PVDF is found to crystallize within the PMMA‐rich matrix. Thermal recycling of these blends promotes homogenization, indicating that such CO2‐altered phase behavior is reversible.SAXS patterns acquired from the 69/31 w/w PMMA/PVDF blend.magnified imageSAXS patterns acquired from the 69/31 w/w PMMA/PVDF blend.
}, number={17}, journal={MACROMOLECULAR CHEMISTRY AND PHYSICS}, author={Walker, TA and Melnichenko, YB and Wignall, GD and Lin, JS and Spontak, RJ}, year={2003}, month={Nov}, pages={2064–2077} }
 @article{walker_melnichenko_wignall_spontak_2003, title={Phase behavior of poly(methyl methacrylate)/poly(vinylidene fluoride) blends with and without high-pressure CO2}, volume={36}, ISSN={["0024-9297"]}, DOI={10.1021/ma030103c}, abstractNote={ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTPhase Behavior of Poly(methyl methacrylate)/Poly(vinylidene fluoride) Blends with and without High-Pressure CO2Teri A. Walker, Yuri B. Melnichenko, George D. Wignall, and Richard J. SpontakView Author Information Departments of Chemical Engineering and Materials Science & Engineering, North Carolina State University, Raleigh, North Carolina 27695, and Condensed Matter Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 Cite this: Macromolecules 2003, 36, 12, 4245–4249Publication Date (Web):May 23, 2003Publication History Received11 February 2003Published online23 May 2003Published inissue 1 June 2003https://pubs.acs.org/doi/10.1021/ma030103chttps://doi.org/10.1021/ma030103crapid-communicationACS PublicationsCopyright © 2003 American Chemical SocietyRequest reuse permissionsArticle Views385Altmetric-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 InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Differential scanning calorimetry,Fluoropolymers,Organic compounds,Polymers,Scattering Get e-Alerts}, number={12}, journal={MACROMOLECULES}, author={Walker, TA and Melnichenko, YB and Wignall, GD and Spontak, RJ}, year={2003}, month={Jun}, pages={4245–4249} }
 @article{walker_semler_leonard_maanen_bukovnik_spontak_2002, title={ABA triblock copolymer gels modified with an A-compatible semicrystalline homopolymer}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la026117d}, abstractNote={In the presence of a midblock-selective solvent, ABA triblock copolymers form physical gels in which bridged and entangled B-chains establish a swollen network stabilized by A-microdomains. Here, we seek to improve the properties of an ABA gel through the addition of an A-compatible, high-molecular-weight semicrystalline homopolymer (shA). Dynamic rheology indicates that the elastic modulus increases substantially, and far beyond that achievable with an inert filler, with increasing shA content at constant solvent concentration. Transmission electron micrographs reveal the existence of nanoscale shA filaments and sheets dispersed in a micelle-stabilized gel network. The shape of the nanoscale shA objects, which are partially crystalline according to differential scanning calorimetry, and their apparent interaction with the A-rich micelles enhance network development and are responsible for the pronounced modulus increase.}, number={22}, journal={LANGMUIR}, author={Walker, TA and Semler, JJ and Leonard, DN and Maanen, GJ and Bukovnik, RR and Spontak, RJ}, year={2002}, month={Oct}, pages={8266–8270} }