Characterization of chemical structure and morphology of eroding polyanhydride copolymers by liquid-state and solid-state H-1 nmr

An n.m.r. investigation of the chemical and morphological changes occurring during erosion in pH 7.4 phosphate buffer at 37 degrees C of melt-fabricat ed polyanhydride devices formed from copolymers of 1,3-bis(p-carboxyphenoxy )propane (CPP) and sebacic acid (SA) is reported. From sequence distributio ns determined using solution-state H-1 n.m.r. spectroscopy, the following o rder of anhydride bond lability was determined. SA-SA approximate to SA-CPP much greater than CPP-CPP, leading to preferential hydrolysis of aliphatic blocks within the copolymer chain. Solid-state H-1 and H-2 n.m.r, spectros copy were used to investigate morphological changes occurring during erosio n. Both indicated significant absorption of mobile water after cn. 10 h. Su btle variations in the symmetry of the narrow signals confirmed the changes in chemical composition apparent from high resolution H-1 n.m.r. analysis. In the initial stages, there was an increase in crystallinity attributed t o preferential erosion of amorphous regions. (C) 1999 Elsevier Science Ltd. All rights reserved.