Effect of temperature and HV monomer concentration on parameters of the unit cell of the PHB/HV biopolymer crystal

Abstract

Changes of the unit cell parameters in the crystalline phase of the poly(β-hydroxy-butyrate-co-valerate) (PHB/HV) containing 0, 6, 15 and 22mol%HV, during heating from room temperature to the melting point, were studied. It was found that unit cell expansion occurred with increasing HV monomer concentration from 0 mol% to 22 mol%. The increase in lattice parameters a and b are almost linear with increasing concentration and the concentrational expansion coefficients in the direction a and b are about 6 × 10-4 (mol%HV)-1 and 3 × 10-4 (mol%HV)-1, respectively. The parameter c (fibre axis) remains unchanged. Temperature change causes unit cell expansion characterized by significant change of the parameter a only, with the linear coefficient of thermal expansion of about 1.3 × 10-40°C-1. © 1997 Elsevier Science Ltd. All rights reserved.