@article{hussain_liu_roberts_2012, title={Synthesis of cross-linked, partially neutralized poly(acrylic acid) by suspension polymerization in supercritical carbon dioxide}, volume={51}, number={35}, journal={Industrial & Engineering Chemistry Research}, author={Hussain, Y. A. and Liu, T. and Roberts, G. W.}, year={2012}, pages={11401–11408} }
 @article{cao_liu_roberts_2010, title={Predicting the Effect of Dissolved Carbon Dioxide on the Glass Transition Temperature of Poly(acrylic acid)}, volume={115}, ISSN={["1097-4628"]}, DOI={10.1002/app.31278}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Cao, Gui-Ping and Liu, Tao and Roberts, George W.}, year={2010}, month={Feb}, pages={2136–2143} }
 @article{liu_desimone_roberts_2006, title={Cross-linking polymerization of acrylic acid in supercritical carbon dioxide}, volume={47}, ISSN={["0032-3861"]}, DOI={10.1016/j.polymer.2006.03.103}, abstractNote={Cross-linking polymerization of acrylic acid in supercritical carbon dioxide (scCO2) was studied in a batch reactor at 50 °C and 207 bar with either triallyl pentaerythritol ether or tetraallyl pentaerythritol ether as the cross-linker and with 2,2′-azobis(2,4-dimethyl-valeronitrile) as the free radical initiator. All polymers were white, dry, fine powders. Scanning electron microscopy showed that the morphology of the polymer particles was not affected by cross-linking. As the cross-linker concentration was increased, the polymer glass transition temperature first decreased, then increased. Water-soluble and water-insoluble polymers were synthesized by adjusting the cross-linker concentration. Viscosity measurements showed that the polymer thickening effect strongly depended on the degree of cross-linking. Finally, cross-linking polymerization of acrylic acid in scCO2 was carried out in a continuous stirred tank reactor. The use of cross-linker decreased the monomer conversion in this system.}, number={12}, journal={POLYMER}, author={Liu, Tao and DeSimone, Joseph M. and Roberts, George W.}, year={2006}, month={May}, pages={4276–4281} }
 @article{liu_desimone_roberts_2006, title={Kinetics of the precipitation polymerization of acrylic acid in supercritical carbon dioxide: The locus of polymerization}, volume={61}, ISSN={["1873-4405"]}, DOI={10.1016/j.ces.2005.11.052}, abstractNote={The precipitation polymerization of acrylic acid (AA) has been carried out at 50 and 70∘C in supercritical carbon dioxide (scCO2), using a continuous stirred-tank reactor. Three kinetic models are compared with experimental data on the rate of polymerization and the viscosity-average molecular weight. The first model, the "solution polymerization" model, is based on the assumption that all reactions: initiation, propagation, and termination, take place in the fluid phase; no reaction takes place in the polymer phase. In the second model, the "surface polymerization" model, chain initiation is assumed to occur in the fluid phase, whereas chain propagation and termination occur in a thin zone on the surface of the polymer particles. The third model, the "interior polymerization" model, is similar to the "surface polymerization" model, except that chain propagation and chain termination take place uniformly throughout each polymer particle. Monomer is assumed to be in phase equilibrium between the supercritical fluid and the polymerization zone. The surface polymerization and interior polymerization models both provide a much better description of the experimental data than the solution polymerization model. This suggests that a significant portion of AA polymerization takes place in the polymer phase, when scCO2 is the reaction medium. However, the data do not support a choice between the surface and interior polymerization models.}, number={10}, journal={CHEMICAL ENGINEERING SCIENCE}, author={Liu, T and DeSimone, JM and Roberts, GW}, year={2006}, month={May}, pages={3129–3139} }
 @article{liu_garner_desimone_roberts_bothun_2006, title={Particle formation in precipitation polymerization: Continuous precipitation polymerization of acrylic acid in supercritical carbon dioxide}, volume={39}, ISSN={["0024-9297"]}, DOI={10.1021/ma061260p}, abstractNote={The morphology of the polymer produced during continuous precipitation polymerization of acrylic acid in supercritical carbon dioxide (scCO2) varied significantly with reaction conditions. Three different morphologies were observed:  a coagulum of primary particles with diameters of 100−200 nm, irregular particles with diameters of 5−20 μm, and spheres with diameters of 10−100 μm. To explore the variables that control particle morphology, the glass transition temperature (Tg) of poly(acrylic acid) (PAA) was measured at several CO2 pressures using high-pressure differential scanning calorimetry. Sorption of scCO2 into PAA also was measured at various temperatures and pressures with a quartz crystal microbalance. Chow's equation described the Tg reduction by CO2 quite accurately. Formation of large spherical particles of PAA was favored when the polymer molecular weight was relatively low and when the polymerization temperature was well above Tg.}, number={19}, journal={MACROMOLECULES}, author={Liu, Tao and Garner, Pamela and DeSimone, Joseph M. and Roberts, George W. and Bothun, Geoffrey D.}, year={2006}, month={Sep}, pages={6489–6494} }
 @article{liu_desimone_roberts_2005, title={Continuous precipitation polymerization of acrylic acid in swercritical carbon dioxide: The polymerization rate and the polymer molecular weight}, volume={43}, ISSN={["1099-0518"]}, DOI={10.1002/pola.20728}, abstractNote={Abstract}, number={12}, journal={JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY}, author={Liu, T and Desimone, JM and Roberts, GW}, year={2005}, month={Jun}, pages={2546–2555} }