The melt polycondensation reaction of trans-4-hydroxy-N-benzyloxycarbonyl-L-proline (N-CBz-Hpr) and functional cyclic esters containing protected functional groups (carboxyl, and amino) at a wide range of molar fractions in the feed produced new degradable poly(N-CBz-Hpr-co-functional-epsilon-CL)s with stannous 2-ethylhexanoate (Sn(Oct)(2)) as a catalyst. The optimal reaction conditions for the synthesis of the copolymers were obtained with 1.5 wt% Sn(Oct)(2) at 140 degreesC for 24 h. The copolymers obtained were characterized by Fourier transform infrared spectroscopy (FT-IR), H-1 NMR, differential scanning calorimetry, gel permeation chromatography, and Ubbelohde viscometry. The copolymers synthesized exhibited oligomeric molecular weights (3000-5000 g mol(-1)) with modestly narrow molecular weight distributions (1.11-1.37). The values of the glass-transition temperature (T-g) of the copolymers depend on the compositions, and the molar fractions of cyclic lactone. For the poly(N-CBz-Hpr-co-4-EtC-epsilon-CL) system, with a decrease in 4-EtC-epsilon-CL contents from 79 to 3 mol%, the T-g increased from -34 to 67 degreesC In vitro degradation of these copolymers was evaluated from weight-loss measurements. (C) 2003 Elsevier Ltd. All rights reserved.