Abiotic aging of water- soluble 3- hydroxybutyric acid oligomers as monitored by capillary zone electrophoresis

Oligomers of poly(3-hydroxybutyric acid) (P(3-HB)) were prepared by partial degradation of high molecular weight P(3-HB) dissolved in 1,2-dichloroethane/water mixture in the presence of p-toluene sulfonic acid (p-TSA). The water-soluble fraction of the resulting oligomers was extracted from the mixture with neutral sodium phosphate buffer. Capillary zone electrophoresis showed that the aqueous extracts were composed of two series of oligomers. The first one was composed of one to seven P(3-HB) oligomers (O(3-HB)). In contrast, the second series was composed of four oligomers characterized by the presence of a terminal C=C bond [O’(3-HB)]. Both series of oligomers behaved differently insofar as their fate in aqueous medium was concerned. The 0(3-HB) compounds were stable over a period of 2 months. On the other hand, the population of the O’(3-HB) oligomers varied, the proportion of oligomers increasing with aging time.