The influence of semicrystalline morphology on the dielectric relaxation properties of poly(3-hydroxybutyrate)

The dielectric relaxation characteristics of poly(3-hydroxybutyrate) (PHB) in the glass-rubber (alpha) relaxation region has been investigated. A series of cold-crystallized samples were examined, with emphasis on the influence of semicrystalline morphology on relaxation properties. The presence of crystallinity had a marked impact on the alpha -relaxation characteristics of the various cold-crystallized specimens as compared to the wholly amorphous material. The constraining influence of the crystallites produced a progressive relaxation broadening and a positive offset in relaxation temperature. With regard to the dielectric relaxation strength, Delta epsilon, we found that the amorphous phase relaxation in the semicrystalline sample had a completely different temperature dependence compared to the wholly amorphous sample, leading to an increase in relaxation strength as the temperature increases above the glass transition temperature (T-g). This was explained by the existence of a rigid amorphous phase interface which relaxes gradually above the T-g of the mobile amorphous material. We suggest that the mobile material is essentially located in the amorphous gaps between lamellar stacks. (C) 2001 Elsevier Science Ltd. All rights reserved.