On the isomorphism of poly(β‐hydroxybutyrate‐co‐β‐hydroxyvalerate) random copolymers

The defect Gibbs energy of hydroxyvalerate comonomer inclusions into the crystals made up by random copolymers of poly(β‐hydroxybutyrate‐co‐β‐hydroxyvalerate) (PHB/HV) is calculated by means of the thermodynamic integration approach. The result obtained for a single inclusion is in excellent agreement with those obtained by fitting experimental melting temperature and cocrystal composition data. Lattice model calculations that cover the whole range of copolymer composition were carried out based on calculations of double inclusion, which revealed a decrease of the average defect Gibbs energy in adjacent defects. On decomposing the Gibbs energy, it is found that the configurational entropy contributes the dominant part of the defect Gibbs energy.