Hydrolytic and fungal degradation of polyamides derived from tartaric acidand hexamethylenediamine

The hydrolytic and fungal degradability of a set of polyamides made from D and L-tartaric acids and 1,6-hexanediamine was investigated as a function o f the enantiomeric composition of the polymers. Optically pure enantiomorph s (100% D and 100% L) as well as a series of stereocopolymers with D:L rati os varying from 1:9 to 1:1 were examined. Hygroscopicity of these polyamide s was found to increase from 8 to 25% when the D:L ratio changed from 0 to 1. Degradation in water under physiological conditions (pH 7.3 and 37 degre es C) took place slowly and also increased with the D:I ratio of the stereo copolymer. Weight loss between 10 and 30% and decays in the molecular weigh t down to nearly 50% were observed after 2 months of incubation. Degradatio n by Aspergillus niger was tested on cast films in the presence of Sabourau d's dextrose broth medium. Fungal attack was evaluated by mycelial coverage and invasion based on standards. Extensive surface growing and a considera ble pervading of the bulk material by the fungi was observed for stereocopo lyamides with D:L ratios 1:4 and 1:1. On the contrary, the microorganism ap peared to be completely inactive in cultures of either of the two optically purl polymers. These results indicated that the dominant factor determinin g the biodegradability of poly(tartaramide)s is water affinity rather than the configurational nature of the polyamide. (C) 2000 Elsevier Science Ltd. All rights reserved.