Structural evolution of poly(butylene succinate) crystals on heating with the formation of a dual lamellar population, as monitored by temperature-dependent WAXS/SAXS analysis

The structural evolution of poly(butylene succinate) (PBS) crystals after crystallization at 100 °C has been investigated by synchrotron wide-angle and small-angle X-ray scattering (WAXS and SAXS) analysis. Isothermal crystallization of PBS leads to a single lamellar population. Temperature-dependent WAXS/SAXS analysis has proven that an additional crystal population, characterized by thicker lamellae, develops upon heating, resulting in a dual lamellar population. Deconvolution of the Lorentz-corrected double SAXS profiles has allowed deriving the temperature dependence of the lamellar thickness for the two different crystal populations. The structural information derived by WAXS/SAXS has allowed elucidating the multiple melting behavior of PBS, so that the separate endotherms of the overall melting behavior could be associated with specific thermal events. The first melting peak has been connected to the fusion of original crystals, only minimally reorganized upon heating, whereas the second melting peak has been ascribed to the overlapping of two different melting processes, one linked to the fusion of original crystals thickened at high temperatures, most likely in the solid state, and the other one to the fusion of markedly thicker crystals, developed via melting/recrystallization mechanism.