Porous biodegradable polyesters. I. Preparation of porous poly(L-lactide) films by extraction of poly(ethylene oxide) from their blends

Abstract

Porous poly(L-lactide) (PLLA) films were prepared by water extraction of poly(ethylene oxide) (PEO) from solution-cast PLLA and PEO blend films. The dependence of blend ratio and molecular weight of PEO on the porosity and pore size of films was investigated by gravimetry and scanning electron microscopy. The film porosity and extracted weight ratio were in good agreement with the expected for porous films prepared using PEO of low molecular weight (Mw = 1 × 103), but shifted to lower values than expected when high molecular weight PEO (Mw = 1 × 105) was utilized. The maximum pore size was larger for porous films prepared from PEO having higher molecular weight, when compared at the same blending ratio of PLLA and PEO before water extraction. Differential scanning calorimetry of as-cast PLLA and PEO blend films revealed that PLLA and PEO were phase-separated at least after solvent evaporation. On the other hand, comparison of blend films before and after extraction suggested that a small amount of PEO was trapped in the amorphous region between PLLA crystallites even after water extraction and hindered PLLA crystallization during solvent evaporation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 629–637, 2000