SYNTHESIS OF BIODEGRADABLE COPOLY(L-LACTIC ACID/AROMATIC HYDROXYACIDS) WITH RELATIVELY LOW-MOLECULAR-WEIGHT

Biodegradable copolyesters having aromatic rings (C6H5, CH2 · C6H5) as side-chain residues, e.g. l-lactic acid (LA)/dl-mandelic acid (MA) and LA/l-3-phenyllactic acid (PheLA), were synthesized by direct copolycondensation without catalyst at 200°. These copolyesters were characterized with respect to composition (1H-NMR spectroscopy), molecular weight (gel permeation chromatography), crystallinity (differential scanning calorimetry) and in vivo degradation (animal experiments). The in vivo degradation pattern changed from a typical parabolic-type to an S-type with increasing aromatic hydroxyacid content in the copolyester and molecular weight of the copolyester. In this case, the degree of in vivo degradation of copoly(LA/PheLA) exceeded that of copoly(LA/MA), because of differences related to the side-chains of aromatic hydroxyacyl units in the copolyesters. © 1990.