Hydrolytic degradation of blends of polyhydroxyalkanoates and functionalized polyhydroxyalkanoates

摘要

The hydrolytic degradation of poly(3-hydroxyalkanoates), PHA, blends with low and high molecular weight additives was examined. The PHA films were characterised by Differential Scanning Calorimetry, DSC, and Atomic Force Microscopy, AFM. The DSC and AFM results revealed that hydrolyzable PLA and hydrophilic PEG, selected as additives which might accelerate hydrolytic degradation, were immiscible with PHAs over the range of compositions studied. PHA blends were incubated in tetraborate buffer (pH = 10) at 37 ℃ for periods ranging from 7 to 160 days. Film degradation was studied by weight loss and Size Exclusion Chromatography (SEC). The results show that the presence of a second component, whatever its chemical nature, is sufficient to perturb the crystallization behavior of highly crystalline poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBHV, and increase hydrolytic degradation. In contrast, the degradation of poly(3-hydroxyoctanoate), PHO, was unaffected by blending with PLA or PEG. PHO degradation is a very slow process, requiring several months of incubation. However, the introduction of polar carboxylic groups in side chains led to an increase in the degradation rate. Carboxylic groups promote water penetration into the polymer.