On the isomorphism of poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) random copolymers

The defect Gibbs energy of hydroxyvalerate comonomer inclusions into the cr ystals made up by random copolymers of poly(beta-hydroxybutyrate-co-beta-hy droxyvalerate) (PHB/HV) is calculated by means of the thermodynamic integra tion approach. The result obtained for a single inclusion is in excellent a greement with those obtained by fitting experimental melting temperature an d cocrystal composition data. Lattice model calculations that cover the who le range of copolymer composition were carried out based on calculations of double inclusion, which revealed a decrease of the average defect Gibbs en ergy in adjacent defects. On decomposing the Gibbs energy, it is found that the configurational entropy contributes the dominant part of the defect Gi bbs energy.