Tyrosine-PEG-derived poly(ether carbonate)s as new biomaterials. Part I: synthesis and evaluation.

Tyrosine PEG-derived poly(ether carbonate)s were prepared by condensation copolymerization with phosgene. The resulting polymers were random copolymers with weight average molecular weights from 40 000 to 200 000 dalton. Chemical structure and purity were confirmed by NMR and FTIR spectral analysis. General structure property correlations were established. The glass transition temperature decreased with increasing PEG content and increasing pendent chain length. When higher molecular weight PEG blocks were used, the glass transition temperature increased relative to identical polymers having shorter PEG blocks. The tensile modulus increased with decreasing PEG content, decreasing pendent chain length, and when longer PEG blocks were used. Water uptake and the rate of backbone degradation increased with increasing PEG content. Microspheres could be prepared by solvent evaporation techniques from copolymers with low PEG content. Release rate of pNA and FITC-dextran from the microspheres increased with increasing PEG content. While tyrosine-derived polycarbonates were excellent substrates for cell attachment and growth, the presence of only 5 mol% of PEG1000 led to low or no cell attachment in short-term cell culture with both rat lung fibroblasts and osteoblasts. The polymers were non-cytotoxic.