Polyethylene glycol-solvolyzed poly-(l)-lactic acids and their stereocomplexes with poly-(d)-lactic acid

Poly-(l)-lactic acid (PLLA) was solvolyzed with polyethylene glycol (PEG) with different ratios of PLLA and PEG under dry conditions. The obtained materials were found to be the block copolymer of PLLA and PEG (PLLA/PEG) from NMR analysis of which the number average molecular weights ranged from 6 × 103 to 2 × 104 g mol−1. The films of stereocomplex (SC) of PLLA/PEG and poly-(d)-lactic acid (PDLA) were prepared by solvent casting method, and the thermal properties and the contact angle of the films were examined. The melting temperatures of PLLA/PEG and the corresponding SC with PDLA linearly decreased with the increase in the PEG content from 110 to 170 °C. The contact angle of PLLA/PEG became lower when the PEG content in the PLLA/PEG was higher, while their SCs with PDLA showed no clear correlation with the PEG content. Biodegradability of PLLA/PEGs and their SCs were also investigated with respect to the EG content.