To investigate the effect of imidazolium ionic liquid with poly(ethylene glycol) segment (IL) on the polar phase crystallization behavior of poly(vinylidene fluoride) (PVDF), a series of PVDF/IL composites were prepared using solution-cast method. The crystallization peak temperature of PVDF composites and the growth speed of samples decrease with increasing of IL. The > CF2 groups in amorphous region are retained and > CF2 groups in crystalline region are liberated by the PEG long soft segments of IL. The intensity of peaks represented as alpha phase reduces, moreover polar phase content increases with increasing of IL. The interaction between the > CF2 and the imidazolium cation can induce the polar phase, and the interaction between the > CF2 and PEG soft segment can strengthen polar crystalline induction. PVDF/12IL composite can form big gamma spherulite circled by beta phase. (C) 2018 Elsevier B.V. All rights reserved.