Demixing Processes in the Precipitation of Semicrystalline Polymers with a Compressed Antisolvent

摘要

Polymer precipitation with compressed or supercritical antisolvents has applications to the production of tailored membrane, microparticles, or fiber morphologies as well as the fractionation of polymers. Increased interest in precipitation processes with compressed or supercritical antisolvents, primarily CO_2, in driven by the potential to achieve unique products or separations, the opportunity to vary these processes with changes in operating temperature or pressure, and the recovery of a dry product following depresurization. The morphology or fractionation achieved by antisolvent precipitation is the product of competing thermodynamic and kinetic processes, which occur during the simultaneous diffusion of the solvent into the antisolvent phase and the antisolvent into the solvent-rich phase. In the case of semicystalline polymers, the polymer morphology or fractionation can be dominated by liquid-liquid demixing; or a competition between the two processes.