Synthesis, characterization, and degradation of copolymer from trans-4-hydroxy-L-proline and L-lactide

A series of novel copolymers of trans-4-hydroxy-L-proline (Hpr) and L-lactide (LLA) were synthesized by ring opening copolymerization, using stannous octoate as a catalyst. These new copolymers have pendant amino functional groups along the polymer backbone chain. Various techniques, including ¹H NMR, IR, DSC, and the use of a Ubbelohde viscometer, were used to elucidate structural characteristics, thermal properties, and degradation behavior of the resulting copolymers. Data showed that the optimal reaction condition for the synthesis of the copolymers was obtained using 3 wt% stannous octoate at 140 °C for 24 h. The DSC analysis demonstrated amorphous structure for most of the copolymers. The glass transition temperatures (T_g) of the copolymers shift to a higher temperature with increasing Hpr/LLA molar ratio. In vitro degradation of these poly(N-CBz-Hpr-co-L-LA) was evaluated by weight loss measurements.