Effect of Chain Stereoconfiguration on Poly(3-hydroxybutyrate) Crystallization Kinetics

Abstract

Poly(3-hydroxybutyrate) (PHB) is naturally accumulated by bacteria but can also be synthesized chemically. Its processability is limited, as it tends to degrade at temperatures above its melting temperature; hence, investigation into crystallization kinetics and morphology of PHB materials of both natural and synthetic origins is of great need and interest to get a better understanding of structure-property relationship. Accordingly, this contribution reports a first study of the crystallization and morphology of synthetic PHB materials of different molecular weights. These synthetic PHBs are racemic mixtures (50/50 mol %) of <i>R</i> and <i>S</i> chain configurations and are compared with an enantiopure bacterial <i>R</i>-PHB. Nonisothermal and isothermal crystallization studies show that <i>R</i> and <i>S</i> chains of PHB can cocrystallize in the same unit cell as the <i>R</i>-PHB. Most significantly, the results show that the presence of <i>S</i> chains decreases the overall crystallization rate, which could enhance the processability and industrialization of PHB-based materials.