The effect of molecular weight on the material properties of biosynthesized poly(4-hydroxybutyrate)

Poly(4-hydroxybutyrate) (P4HB) is a bacterial polyhydroxyalkanoate with interesting biological and physico-chemical properties for the use in biomedical applications. The synthesis of P4HB through a fermentation process often leads to a polymer with a too high molecular weight, making it difficult to process it further by solvent- or melt-processing. In this work P4HB was degraded to obtain polymers with a molecular weight ranging from 1.5×10(3)g/mol to 1.0×10(6)g/mol by using a method established in our laboratory. We studied the effect of the change in molecular weight on thermal and mechanical properties. The decrease of the molecular weight led to an increase in the degree of crystallinity of the polymer. Regarding the tensile mechanical properties, the molecular weight played a more prominent role than the degree of crystallinity in the evolution of the properties for the different polymer fractions. The method presented herein allows the preparation of polymer fractions with easier processability and still adequate thermal and mechanical properties for biomedical applications.