Intermolecular interactions in poly(vinylidene fluoride) and ε-caprolactam mixtures

Mixtures of poly(vinylidene fluoride) (PVDF) and caprolactam (CPL) have been investigated as models for possible cross-interactions between vinylidene fluoride and amide structural units, that might account for the very fine phase morphology previously observed in PVDF/polyamide 6 blends. Over the entire composition range, the PVDF/CPL mixtures are monophase above the PVDF melting temperature. From the depression of the PVDF melting point, a negative interaction energy density, B, has been calculated that, however, depends on both temperature and CPL concentration. Mutual solubility of PVDF and CPL and negative B values are consistent with specific intermolecular interactions whose nature is discussed.