Polymorphic Extended-Chain and Folded-Chain Crystals in Poly(vinylidene fluoride) Achieved by Combination of High Pressure and Ion–Dipole Interaction

Abstract

Manipulating polymorphism in extended chain-crystals (ECCs), which are commonly achieved by crystallization under high pressures, is important for enriching our understanding of basic polymer crystallization as well as for achieving high performance materials. In this study, the influence of high pressure and ion–dipole interaction on the polymorphism was investigated by comparing neat poly(vinylidene fluoride) (PVDF) and PVDF with 1 wt % cetyltrimethylammonium bromide (CTAB) nonisothermally crystallized from the melt at 210 °C. Under low pressures (≤10 MPa), γ folded-chain crystals (FCCs), rather than α FCCs, were obtained for PVDF/1 wt % CTAB because of the ion–dipole interaction. Under a moderate pressure (100 MPa), pure β FCCs were formed in PVDF/1 wt % CTAB, owing to the synergistic effect of both high pressure and ion–dipole interaction. Under high pressures (≥200 MPa), mixtures of β/γ FCCs and ECCs were obtained for PVDF/1 wt % CTAB. This was different from the neat PVDF, where mixtures of α FCCs a...