A synchrotron SAXS study of miscible blends of semicrystalline poly(vinylidenefluoride) and semicrystalline poly(1,4‐butylene adipate). II. Crystallization,morphology, and PBA inclusion in PVF2 spherulites

The incorporation of poly(1,4‐butylene adipate) (PBA) and its crystallization behavior within poly(vinylidenefluoride) (PVF₂) spherulites in miscible PVF₂/PBA blends have been further studied with small‐angle X‐ray synchrotron scattering (SAXS). The incorporation of PBA into the PVF₂ interlamellar region was found to be dependent on the PVF₂ crystallization conditions. In our previous work, where the blends were crystallized by a one‐step quenching process directly from 190 (a single‐phase region) to 20 °C (a three‐phase region), the transition from PBA inclusion in the PVF₂ interlamellar region to interlamellar exclusion occurred at a PBA weight fraction of ∼ 0.5. In this case, where the blends were first quenched from 190 (a single‐phase region) to 130 °C (a two‐phase region) and then further quenched to 20 °C (a three‐phase region), the transition occurred at a PBA weight fraction of less than 0.3. That is, when a blend is crystallized under different conditions, different amounts of the PBA component are incorporated into the PVF₂ interlamellar phase. The thickness of the PVF₂ interlamellar phase, in turn, may affect the PBA crystalline structure in the interlamellar region. Time‐resolved SAXS was used to probe the crystallization dynamics of both PVF₂ and PBA components in a blend containing 60 wt % PBA. The blend was quenched from the single‐phase region at 190 to 130 °C to crystallize the PVF₂ component and was then further quenched to 20 °C to crystallize the PBA component. This study, together with our earlier results, shows that the time dependence of the PVF₂ crystallization rate and crystalline lamellar thickness is a function of the PBA content in the blend. The glass‐transition temperature of the blend and the PBA diffusion process are the two dominant factors that control the PVF₂ crystallization dynamics. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2296–2308, 2000