Precipitation of PMMA/PCL blends using supercritical carbon dioxide

Solutions of a poly(methyl methacrylate)–poly(ε‐Caprolactone) (PMMA/PCL) polymer blend in dichloromethane (DCM) and mixtures of the same polymer blend and cholesterol in DCM were sprayed into supercritical carbon dioxide. Carbon dioxide was contacted with 0.23–1 wt % polymer solutions and with 0.3–1 wt % polymer plus 0.1–0.6 wt % cholesterol solutions in a continuous mode of operation. Pressure and temperature were constant for almost all of the experiments, 11 MPa and 314 K, respectively. Fibrous networks composed of many smaller microfibrils were obtained by spraying the different solutions through a conical nozzle into concurrently flowing supercritical carbon dioxide. This morphology suggests such an important degree of agglomeration that primary particles are no longer discernible. Processing the polymers with CO₂ leads to the removal of contaminants as the precipitate was free of monomer and initiator. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2422–2426, 2004