Crystallization induced microstructure of crystalline/crystalline poly(vinylidenefluoride)/poly(3-hydroxybutyrate) blends probed by small angle x-ray scattering

The lamellar morphology of a melt-miscible blend consisting of two crystalline constituents, poly(vinylidene fluoride) (PVDF) and poly(3-hydroxybutyrate) (PHB), has been investigated by small angle X-ray scattering (SAXS). Owing to the proximity of melting points, PVDF and PHB crystallized over essentially the same temperature range, and consequently created a crystalline/crystalline state with the morphology characterized by the spatial arrangement of PVDF and PHB lamellae. Irrespective of the crystallization temperatures (T_c), the SAXS patterns revealed the presences of two lamellar stack (LS) domains, where one contained mainly PVDF lamellae (PVDF LS domain) and the other primarily consisted of PHB lamellae (PHB LS domain). The interlamellar (IL) regions of both LS domains were found to contain mixed amorphous PVDF and PHB. The blends crystallized at higher T_c exhibited smaller SAXS invariants. This observed T_c dependence was connected with the disparity in crystallization kinetics that gave rise to different LS domain sizes at different T_cs.