Supernucleation, crystalline structure and thermal stability of bacterially synthesized poly(3-hydroxybutyrate) polyester tailored by thymine as a biocompatible nucleating agent

Naturally occurring thymine (TM) was incorporated into bacterial poly(3-hydroxybutyrate) (PHB) polyester to fabricate a novel and green biocomposite. Both 0.5% and 1% TM exhibit supernucleation effect on PHB, and crystallization kinetics suggests TM significantly increased T-c and X-c, and substantially shortened t(1/2) of PHB. Epitaxial nucleation caused by a perfect crystal lattice matching between PHB and TM, was proposed to elucidate nucleation mechanism of PHB. Hydrogen bond interaction exists between C=O, C-O-C groups of PHB and -CH3 (or -CH)/-NH- group of TM. TM interacted with C=O group of PHB crystalline phase rather than that of amorphous one. In addition, two new IR crystalline bands assigned to C-O-C group of PHB appeared in the presence of TM, which arises from shift of two amorphous ones, respectively. TM enhanced onset thermal degradation temperature of PHB, mainly attributed to increased degree of crystallinity of PHB and flame retardance effect of TM. (C) 2020 Elsevier B.V. All rights reserved.