Aliphatic polyesters and their copolymers synthesized through direct condensation polymerization

Copolymers of lactic acid and the other hydroxyacid, such as glycolic acid and 6-hydroxyhexanoic acid, were prepared in an organic solvent through the direct condensation. Glass-transition temperatures and melting points of these polymers are slightly different from those of polymers obtained by the ring-opening polymerization process. The other type polyesters from dicarboxylic acids and diols that have molecular weights of up to 300 000 were also prepared by the same method. The high-molecular-weight polyester obtained can be processed into films and molded products of a sufficient strength and toughness. Copolymers synthesized from the reaction of polylactic acid and the other aliphatic polyesters or cellulose derivative were also discussed. (C) 1998 Elsevier Science Limited. All rights reserved.