Blends of aliphatic polyesters. VI. Lipase-catalyzed hydrolysis and visualized phase structure of biodegradable blends from poly(epsilon-caprolactone) and poly(L-lactide)

Phase-separated biodegradable polymer blends were prepared from poly(epsilo n -caprolactone) (PCL) and poly(L-lactide) (PLLA), and Rhizopus arrhizus li pase-catalyzed hydrolysis and phase structure of the blend films were inves tigated. Gravimetry revealed that the lipase-catalyzed hydrolysis of PCL in PCL- and PLLA-rich phases is disturbed by the presence of PLLA. Polarimetr y confirmed the occurrence of a predominant hydrolysis of PCL and subsequen t removal of the hydrolyzed water-soluble PCL oligomers in the blend films. Gravimetry and gel permeation chromatography of the non-blended PLLA film indicated that R. arrhizus lipase has no catalytic effect on the hydrolysis of PLLA. The phase structure of the blend films could be visualized by sel ective enzymatic removal of one component and subsequent scanning electron microscopic observation. (C) 2001 Elsevier Science BN. All rights reserved.