Hydrolytic degradation of poly(DL-lactic acid) in the presence of caffeine base

摘要: Abstract The mechanism of hydrolytic degradation poly( dl -lactic acid) (PLA 50 ) matrix was examined in the presence a tertiary amine, namely caffeine, order to elucidate influence this basic compound on cleavage polyester chains. Caffeine incorporated into PLA various contents (0 20%) by blending acetone followed solvent evaporation. resulting blends were processed 1.5 mm thick plates and 0.3 thin films compression moulding. Degradation carried out under standardized conditions, i.e. isoosmolar pH 7.4 phosphate buffer at 37°C. effects caffeine characteristics rather complex largely depended blend composition. For low (≤ 2%), it is suggested that molecularly dispersed matrices accelerated considerably with respect caffeine-free devices. However, increase rate not proportional content due combined base/carboxyl end group interaction, crystallization matrix-controlled or channeling-controlled diffusion caffeine. In early stages degradation, overall catalytic effect larger for devices than highly loaded ones where crystallized state thus less available catalysis. At later stages, however, neutralization carboxyl groups became predominant governed case From general viewpoint, degraded slightly faster films. Moreover, crystalline residues composed oligomeric stereocomplex obtained both