Water-soluble poly(ester-carbonate) having pendent amino and carboxylic groups on the main-chain carbon is reported for the first time. This article describes the melt ring-opening/condensation reaction of trans-4-hydroxy-N-benzyloxycarbonyl-L-proline (N-CBz-Hpr) with 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC) at a wide range of molar fractions. The influence of reaction conditions such as catalyst concentration, polymerization time, and temperature on the number average molecular weight (M.) and molecular weight distribution (M-w/M-n,) of the copolymers was investigated. The polymerizations were carried out in bulk at 110 degreesC with 3 wt % stannous octoate as a catalyst for 16 h. The poly(ester-carbonate)s obtained were characterized by Fourier transform infrared spectroscopy, H-1 NMR, differential scanning calorimetry, and gel permeation chromatography. The copolymers synthesized exhibited moderate molecular weights (M-n = 6000-14,700 g mol(-1)) with reasonable molecular weight distributions (M-w/M-n, = 1.11-2.23). The values of the glass-transition temperature (T.) of the copolymers depended on the molar fractions of cyclic carbonate. When the MBC content decreased from 76 to 12 mol %, the T-g increased from 16 to 48 degreesC. The relationship between the poly(N-CBz-Hpr-co-MBC) Tg and the compositions was in approximation with the Fox equation. In vitro degradation of these poly(N-CBz-Hprco-MBC)s was evaluated from weight-loss measurements and the change of M. and M-w/M-n. Debenzylation of 3 by catalytic hydrogenation led to the corresponding linear poly(ester-carbonate), 4, with pendent amino and carboxylic groups. (C) 2004 Wiley Periodicals, Inc.