STRUCTURE AND MORPHOLOGY OF SOLID LACTIDE-GLYCOLIDE COPOLYMERS FROM C-13 NMR, INFRARED AND RAMAN-SPECTROSCOPY

The chemical composition, morphology and configuration of a series of solid lactide-glycolide copolymers (PLA(X)GAy: X, % L-lactide and Y, % glycolide) were studied by solid state C-13 n.m.r., infra-red and Ram an spectroscopy. Chemical composition was evaluated from the relative intensities of CH2 and CH carbon n.m.r. peaks and from the intensity r atio of delta CH2 and delta(as)CH(3) bending Raman peaks. Relationship s with GA% content were compared. Raman spectroscopy appeared more sen sitive to the stereochemistry of copolymers than CP/ MAS C-13 n.m.r.. It allowed discrimination of amorphous PLA(42.5)GA(15) from PLA(85)GA( 15), and PLA(37.5)GA(25) from PLA(75)GA(25) based on the new band at a pproximate to 1334 cm(-1) assigned to delta CH bending modes relative to D-LA units. In contrast, solid state C-13 n.m.r. did not allow dist inguishing the specific L- and D,L-LA unit distribution present in the terpolymers. (C) 1998 Elsevier Science Ltd. All rights reserved.