Time-resolved synchrotron small-angle X-ray scattering measurements have been performed during the heating and melting of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate). A rapid, continuous rise in d-spacing was observed during melting, consistent with the disappearance of thinner, unstable crystals from stacks of lamellae possessing a broad distribution of thicknesses. The thickening of the remaining crystals has been characterized during the annealing of a copolymer close to its melting temperature. Differential scanning calorimetry measurements have indicated the presence of multiple melting endotherms in the case of the copolymer but not in the homopolymer. These multiple endotherms have been related to the effects of the hydroxyvalerate units in limiting the thickness of the lamellae at any given temperature.
- X-ray scattering
- differential scanning calorimetry
- thermal effects