Synthesis and characterization of novel poly(estercarbonate)s by copolymerization of trans-4-hydroxy-l-proline with cyclic carbonate

The melt ring-opening/condensation reaction of trans-4-hydroxy-N-benzyl-oxycarbonyl-L-proline (N-CBz-Hpr) with cyclic carbonate [trimethylene carbonate (tri-MC) or tetramethylene carbonate (tetra-MC)] at a wide range of molar fractions in the feed produced new degradable poly(ester-carbonate)s. The influence of reaction conditions such as polymerization time and temperature on the yield and inherent viscosity of the copolymers was investigated. The polymerizations were carried out in bulk at 140 °C with 1.5 wt % stannous octoate as a catalyst for 30 h. The poly(ester-carbonate)s obtained were characterized by Fourier transform infrared spectroscopy, ¹H NMR, differential scanning calorimetry, gel permeation chromatography, and Ubbelohde viscometry. The copolymers synthesized exhibited moderate molecular weights with rather narrow molecular weight distributions. The values of the glass-transition temperature (T_g) of the copolymers depend on the molar fractions of cyclic carbonate. For the poly(N-CBz-Hpr-co-tri-MC) system, with a decreased tri-MC content from 93 to 16 mol %, the T_g increased from -10 to 60 °C. Similarly, for the poly(N-CBz-Hpr-co-tetra-MC) system, when the tetra-MC content decreased from 80 to 8 mol %, the T_g increased from -18 to 52 °C. The relationship between the poly(N-CBz-Hpr-co-tri-MC) T_g and the compositions was in approximation with the Fox equation. In vitro degradation of these poly(N-CBz-Hpr-co-tri-MC)s was evaluated from weight-loss measurements.