Polymer-based nanostructures can be generally created by self-assembly of block copolymers that are commonly synthesized by living radical polymerization. In this study, a new strategy is proposed to fabricate block-like copolymers by using the template of binary phase structure of semicrystalline polymers. Poly(vinylidene fluoride) (PVDF) is thermodynamically miscible with an unsaturated ionic liquid (IL) (1-vinyl-3-ethylimidazolium tetrafluoroborate) in the melt and IL molecules are expelled out from the crystalline parts during the crystallization of PVDF. Therefore, the IL molecules are only located at the amorphous region of PVDF crystals. The electron beam irradiation of the IL incorporated PVDF leads to the local grafting of IL molecules onto the PVDF molecular chains in the amorphous region, so block-like grafting polymer chains of crystalline PVDF-b (amorphous PVDF-g-IL)-b-crystalline PVDF can be achieved. The subsequent heating of the irradiated sample induces the microphase separation of PVDF-g-IL from the ungrafted PVDF chains.