GLYCINE GLYCOLIC ACID-BASED COPOLYMERS

Glycine/glycolic acid based biodegradable copolymers have been prepare d by ring-opening homopolymerization of morpholine-2,5-dione, and ring -opening copolymerization of morpholine-2, 5-dione and glycolide. The homopolymerization of morpholine-2,5-dione was carried out in the melt at 200-degrees-C for 3 min using stannous octoate as an initiator, an d continued at lower reaction temperatures (100-160-degrees-C) for 2-4 8 h. The highest yields (60%) and intrinsic viscosities ([eta] = 0.50 dL/g; DMSO, 25-degrees-C) were obtained after 3 min reaction at 200-de grees-C and 17 h at 130-degrees-C using a molar ratio of monomer and i nitiator of 1000. The polymer prepared by homopolymerization of morpho line-2,5-dione was composed of alternating glycine and glycolic acid r esidues, and had a glass transition temperature of 67-degrees-C and a melting temperature of 199-degrees-C. Random copolymers of glycine and glycolic acid were synthesized by copolymerization of morpholine-2,5- dione and glycolide in the melt at 200-degrees-C, followed by 17 h rea ction at 130-degrees-C using stannous octoate as an initiator. The mor phology of the copolymers varied from semi-crystalline to amorphous, d epending on the mole fraction of glycolic acid residues incorporated. (C) 1994 John Wiley & Sons, Inc.