Behavior of poly(methyl methacrylate)–based systems in supercritical CO₂ and CO₂ plus cosolvent: Solubility measurements and process assessment

Abstract

Abstract Microspheres based on synthetic polymers such as poly(methyl methacrylate) (PMMA) and PMMA blends are known for their medical and optical applications. The development of methods for processing polymeric microspheres using a nontoxic solvent, like supercritical carbon dioxide (SCCO 2 ), is desirable. This work investigates the solubility and behavior of polymers (PMMA and PMMA/polycaprolactone blend) and solutes (cholesterol and albumin) in SCCO 2 and SCCO 2 + cosolvent (acetone, ethanol, and methylene chloride). The knowledge of solubility behavior of materials in SCCO 2 aids in the selection and/or design of the most appropriate technique for materials processing. Processing PMMA‐based polymers with pure SCCO 2 leads to polymer swelling. The lack of polymer solubility in pure CO 2 precludes their micronization by the RESS (rapid expansion of supercritical solutions) process, but on the other hand allows their impregnation. Polymer plasticization caused by CO 2 can be exploited in the PGSS (particles from gas‐saturated solutions) process. Addition of a liquid cosolvent to CO 2 enhances the dissolution of solutes and polymers. Precipitation of the studied polymers by antisolvent techniques seems feasible only by use of CO 2 + methylene chloride. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3652–3659, 2003