Synthesis and characterization of novel biodegradable triblock copolymers from L-Lactide,glycolide, and PPG

Copolymers with a PPG center block and two arms of random glycolide/lactide copolymers have been synthesized and characterized. Compared to random glycolide/lactide copolymers, these new polymers have high toughness and low elastic modulus.¹ H-NMR spectral lines of glycolide CH₂ protons of the copolymers are essentially identical. These materials show no crystallization transition in DSC thermograms and their melting points with respect to PLLA appeared at lower temperatures, indicating the pivotal role of the PPG center block in the copolymer. Degradation in aqueous media (pH = 6.9, 70°C) with stirring, subjected the two end blocks to hydrolytic degradation. The glycolyl ester bond cleavage was faster than for the lactyl ester bond. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 633–637, 1999