Three-step synthesis of a condensation polymer incorporating natural PHB fragments: Structural and physicochemical characterization

Abstract

Poly(3-hydroxybutyrate) (PHB) attracts considerable scientific attention due to its outstanding biodegradability and biocompatibility. However, it lacks certain important properties required for widespread use in medical applications. One of the main drawbacks of PHB is its high degree of crystallinity, which arises from its highly ordered chemical structure. In this study, a three-step synthetic approach that enables disruption of the regular structure of PHB is presented. The approach involves the transesterification of PHB to form oligoester diols, followed by their esterification with cyclic adipic anhydride and subsequent polycondensation with 1,4-butanediol. As a result, a series of terpolyesters containing PHB segments and structural units derived from 1,4-butanediol and adipic acid was obtained. Since the degree of polymerization in polycondensation reactions is highly sensitive to substrate purity, the products of each step were rigorously characterized using NMR spectroscopy. The obtained PHB-based terpolyesters were analyzed by DSC, TGA, XRD, contact angle measurements, and in vitro cytotoxicity assays. The findings indicate that the introduction of short-chain comonomer units into the PHB main chain is an effective strategy for reducing its crystallinity and improving its thermal properties, thus expanding its potential biomedical applications.