@misc{desimone_siripurapu_khan_spontak_royer_2010, title={Nano-and micro-cellular foamed thin-walled material, and processes and apparatuses for making the same}, volume={7,658,989}, number={2010 Feb. 9}, author={DeSimone, J. M. and Siripurapu, S. and Khan, S. A. and Spontak, R. J. and Royer, J.}, year={2010} }
 @article{siripurapu_desimone_khan_spontak_2005, title={Controlled foaming of polymer films through restricted surface diffusion and the addition of nanosilica particles or CO2-philic surfactants}, volume={38}, ISSN={["1520-5835"]}, DOI={10.1021/ma047991b}, abstractNote={Synergistic use of surface barriers and nanoscale additives is investigated as alternate means by which to promote bubble nucleation in, and thus improve the porosity of, poly(methyl methacrylate) (PMMA) thin films (i) constrained between impenetrable plates, (ii) modified with either nanosilica particles, commercial short-chain fluorosurfactants, or designer CO2-philic block/graft copolymers, and (iii) exposed to high-pressure CO2. Resultant foamed films exhibit a vast array of micro/mesocellular morphologies in the presence of supercritical, as well as liquid, CO2 and demonstrate that copolymer micelles afford better control over bubble nucleation (with pore cell densities, N, approaching 1012 cells/cm3) relative to hard nonporous nanoparticles, which alone increase N by more than 2 orders of magnitude at low CO2 pressures. Incorporation of these nanoscale additives in a surface-constrained polymer matrix serves to enhance foaming through concurrent restriction of CO2 diffusion, heterogeneous nucleation...}, number={6}, journal={MACROMOLECULES}, author={Siripurapu, S and DeSimone, JM and Khan, SA and Spontak, RJ}, year={2005}, month={Mar}, pages={2271–2280} }
 @article{siripurapu_desimone_khan_spontak_2004, title={Low-temperature, surface-mediated foaming of polymer films}, volume={16}, ISSN={["1521-4095"]}, DOI={10.1002/adma.200306068}, abstractNote={Ultraporous thin polymer films (see Figure) are generated using physical constraints imposed by external surfaces (hard plates) and internal surfaces (hard nanoparticles and soft micelles) via foaming with supercritical CO2. The constraints serve as diffusion barriers and/or heterogeneous nucleation sites. Use of CO2‐philic copolymers further enables microcellular foaming at reduced pressures with liquid CO2.}, number={12}, journal={ADVANCED MATERIALS}, author={Siripurapu, S and DeSimone, JM and Khan, SA and Spontak, RJ}, year={2004}, month={Jun}, pages={989-+} }
 @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{siripurapu_coughlan_spontak_khan_2004, title={Surface-constrained foaming of polymer thin films with supercritical carbon dioxide}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma0484983}, abstractNote={Microcellular polymer foams afford a wide variety of attributes relative to their dense analogues, and efforts remain underway to establish viable routes to generate foams with substantially reduced pore cell size and increased pore cell density. Barrier constraints are applied in the present work to achieve diffusion-controlled isothermal foaming of thin polymer films in the presence of supercritical carbon dioxide (scCO2). Poly(methyl methacrylate) (PMMA) films measuring ca. 95−100 μm in thickness are physically constrained between two impenetrable plates so that scCO2 exit diffusion is restricted to the film edges. Results obtained here demonstrate that the pore size can be systematically reduced to less than 100 nm in such systems by applying high saturation scCO2 pressures, relatively low foaming temperatures (near the glass transition temperature of the scCO2-plasticized polymer), and a rapid pressure quench. Classical nucleation theory (CNT) modified to account for the compressible nature of scCO2 ...}, number={26}, journal={MACROMOLECULES}, author={Siripurapu, S and Coughlan, JA and Spontak, RJ and Khan, SA}, year={2004}, month={Dec}, pages={9872–9879} }
 @article{siripurapu_gay_royer_desimone_spontak_khan_2002, title={Generation of microcellular foams of PVDF and its blends using supercritical carbon dioxide in a continuous process}, volume={43}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(02)00407-X}, abstractNote={Use of supercritical carbon dioxide (scCO2) as a blowing agent to generate microcellular polymer foams (MPFs) has recently received considerable attention due to environmental concerns associated with conventional organic blowing agents. While such foams derived from amorphous thermoplastics have been previously realized, semicrystalline MPFs have not yet been produced in a continuous scCO2 process. This work describes the foaming of highly crystalline poly(vinylidene fluoride) (PVDF) and its blends with amorphous polymers during extrusion. Foams composed of neat PVDF and immiscible blends of PVDF with polystyrene exhibit poor cell characteristics, whereas miscible blends of PVDF with poly(methyl methacrylate) (PMMA) yield foams possessing vastly improved morphologies. The results reported herein illustrate the effects of blend composition and scCO2 solubility on PVDF/PMMA melt viscosity, which decreases markedly with increasing PMMA content and scCO2 concentration. Morphological characterization of microcellular PVDF/PMMA foams reveals that the cell density increases as the PMMA fraction is increased and the foaming temperature is decreased. This study confirms that novel MPFs derived continuously from semicrystalline polymers in the presence of scCO2 can be achieved through judicious polymer blending.}, number={20}, journal={POLYMER}, author={Siripurapu, S and Gay, YJ and Royer, JR and DeSimone, JM and Spontak, RJ and Khan, SA}, year={2002}, month={Sep}, pages={5511–5520} }