Real-Time Synchrotron SAXS and WAXD Studies on Annealing Behavior of Poly[(R)-3-hydroxybutyrate] Single Crystals

Abstract

Poly[(R)-3-hydroxybutyrate] (P(3HB)) single crystals were grown isothermally at different crystallization temperatures (Tcs) in a dilute solution. Structural changes of the sedimented single-crystal mats on heating were followed by real-time synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques, and the dependence of the annealing behavior on Tc was examined. The two-dimensional (2D) SAXS pattern clearly demonstrated that the P(3HB) single crystal exhibits a discontinuous increase in the lamellar thickness at an annealing temperature. The onset of the discontinuous thickening depended on Tc or the initial lamellar thickness. The discontinuous thickening occurred at higher temperature as the initial lamellar thickness increased. In the transition region where the discontinuous thickening progressed, the new scattering peak intensity increased while the original one decreased. On the other hand, the crystallinity, estimated from the 2D WAXD patterns, first decrea...