STUDIES ON SEQUENCE DISTRIBUTION OF ALIPHATIC AROMATIC COPOLYESTERS BY HIGH-RESOLUTION C-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY FOR EVALUATION OF BIODEGRADABILITY/

Copolyesters with different stoichiometric compositions, obtained from 1,4-butanediol, adipic acid, and terephthalic acid by molten-state po lycondensation, are studied by means of high resolution C-13 NMR spect roscopy with respect to copolymer composition and block length distrib ution. The ratio of aliphatic and aromatic dicarboxylic acids in the p olymer, which sensitively influences the biodegradability of the polym ers, reflects the initial monomer composition during polycondensation. This indicates that under the conditions applied for polycondensation no loss for example of terephthalic acid due to sublimation occurs. I t was found that the aliphatic and aromatic repeating units are random ly distributed within the polymer chain. The experimentally determined average sequence length distribution dependence on stoichiometric cop olymer compositions are in accord with ideal polycondensation statisti cs. In combination with the results of the degradability of aromatic o ligomers, predictions about the degradation characteristics of the ali phatic/aromatic copolymers can be made.