Synthesis and characterization of self-healing bio-based polyurethane from microbial poly(3-hydroxybutyrate) produced in methanotrophs

Poly(3-hydroxybutyrate) (PHB) is an important class of renewable and biodegradable polymers that have recently attracted significant interest. However, the limitations of the physical properties of PHB, owing to its brittle nature, hinder its application in versatile polymers. In this study, we propose an efficient conversion of microbial PHB produced and recovered from methanotrophs to produce the oligomer PHB-diol. The PHB transesterification was conducted using different alcohols and the reaction conditions were optimized to obtain a liquid-like PHB-diol product, a low-molar-mass polyol with a molecular weight of 1000-1400 g/mol for polyurethane (PU) synthesis. A comprehensive characterization of PU samples made from PHB-derived polyol suggested that it could be a viable substitute for 50 wt% traditional petroleum-derived polyol in PU synthesis. In contrast to petroleum-based PU, the synthetic PU film made from microbiologically generated PHB-diol showed noteworthy self-healing ability with a healing efficiency of up to 91.08 % at moderate temperatures after a simple drying process. Self-healing ability is highly desirable and significant for the sustainable manufacturing of advanced materials from bioresources for a wide range of practical applications in electronic devices, coatings, biomedicine, and aerospace.