Effect of different experimental conditions on biodegradable polylactide membranes prepared with supercritical CO2 as nonsolvent

There is increasing interest in the application of supercritical CO₂ (SCCO₂) in the preparation of polymer membranes. Membrane formation with SCCO₂ as a nonsolvent is analogous to the conventional immersion precipitation process using an organic nonsolvent. Polylactide membranes were prepared with SCCO₂ as the nonsolvent under different experimental conditions such as different polymer concentrations, different depressurization rates, and different nonsolvent compositions. The effects of these conditions on the cross‐sectional structure were investigated through scanning electron microscopy. In addition, solvent‐induced crystallization and CO₂‐induced crystallization were studied. The crystallinity of PLA membranes prepared with different solvents or at different pressures was characterized by wide‐angle X‐ray diffraction and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 831–837, 2005