Facile and effective promotion of β crystalline phase in poly(vinylidene fluoride) via the incorporation of imidazolium ionic liquids

Abstract In this study, a facile and efficient protocol to enhance the β‐phase content of poly(vinylidene fluoride) (PVDF) is developed, in which the effect of room temperature ionic liquids (RTILs), including [1‐butyl‐3‐methylimidazolium (bmim)][PF 6 ], [bmim][BF 4 ], [bmim][FeCl 4 ] and [bmim][Cl], on the crystallization behavior of PVDF is investigated. The resulting PVDF/RTIL hybrids are characterized by Fourier transform infrared (FTIR) spectroscopy, XRD, polarized optical microscopy (POM) and DSC. The FTIR spectroscopy and XRD results show that the fraction of β‐phase, F (β), is significantly enhanced by the incorporation of RTILs, specifically from 49.2% for neat PVDF to 92.6% for hybrid filled with 15 wt% [bmim][PF 6 ]. The analysis of the crystallization behavior based on the DSC tests reveals that the degree of crystallinity increases with incorporation of RTILs, implying that RTILs could act as directing agents to facilitate the crystallization process, which is further evidenced by the POM results. In addition, the non‐isothermal crystallization kinetics of PVDF and PVDF/RTIL composites are investigated by means of DSC and the results indicate that the addition of the RTILs significantly influences the mechanism of nucleation and growth of PVDF crystallites. © 2013 Society of Chemical Industry