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The effects of incorporating two imidazolium-type ionic liquids (ILs), 1-vinyl-3-butyl­imidazolium bis­(trifluoro­methylsulfonyl)­imide (IL-TFSI) and 1-vinyl-3-butyl­imidazolium chloride (IL-Cl), on the crystal forms and phase microstructures of poly­(vinylidene fluoride-co-hexafluoro­propylene), P­(VDF-co-HFP), were investigated. No change in the crystal form was observed with the incorporation of IL-TFSI because of the selective interaction between the IL and HFP moieties of the P­(VDF-co-HFP) molecular chains. In contrast, the incorporation of IL-Cl induces an α-to-β crystal form transition because of the interactions between IL-Cl and the VDF moieties. Furthermore, the incorporation of IL-TFSI led to distinct phase separation of P­(VDF-co-HFP), whereas a homogeneous phase structure was maintained with the incorporation of IL-Cl. Element mapping images reveal that the specific interactions of IL-TFSI with the HFP moieties induce enrichment of the HFP moieties, which results in well-defined HFP/IL-TFSI nanodomains in the P­(VDF-co-HFP) matrix. In contrast, a homogeneous morphology was observed in the P­(VDF-co-HFP)/IL-Cl blends. The smaller Cl– anion of IL-Cl can interact with VDF moieties and form a thermodynamically miscible state with the P­(VDF-co-HFP) matrix. In addition, ILs chemically grafted on P­(VDF-co-HFP) were in situ synthesized using electron-beam irradiation of the blends of P­(VDF-co-HFP) with ILs at room temperature because both ILs contain double bonds. The phase structures of the IL-grafted copolymers were further studied. After chemical grafting and melting, the original microphase-separated structure of the P­(VDF-co-HFP)/IL-TFSI blends was maintained, whereas discrete nanodomains with diameters of 10–20 nm were formed for the original homogeneous P­(VDF-co-HFP)/IL-Cl blends. The interesting crystal forms and phase structures of P­(VDF-co-HFP) physically or chemically incorporated with different ILs demonstrate the effectiveness of this strategy for the design of polymer microstructures using simple blending and radiation-induced grafting processes.

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Much attention has been paid on promotion of Poly(L-lactic acid) (PLLA) crystallization. The incorporation of nucleation agents is a commonly used way to enhance the PLLA crystallization. In this work, we reported another efficient strategy to accelerate PLLA crystallization by the conformational pre-ordering of PLLA molecular chains in melt. The organic salt bis(trifluoromethysulfonyl)imide lithium salt (LiTFSI) was incorporated into PLLA and the effects of LiTFSI on the crystallization of PLLA were investigated. It was found that LiTFSI is thermodynamically miscible with PLLA and the anion of LiTFSI interacts with PLLA molecular chains strongly. Small amount of LiTFSI can accelerate the crystallization of PLLA drastically and 0.5 wt % addition gives the best nucleation effects for PLLA. The in situ Fourier transform infrared spectroscopy results revealed that the pre-ordering structure of PLLA chains was formed in the melt with the incorporation of LiTFSI. It was clearly demonstrated that the relative population of gt conformer (corresponding to 10 3 helical conformation of α-form PLLA crystal) in PLLA/LiTFSI composites was higher than that of neat PLLA because of the interactions between LiTFSI and PLLA. Therefore, a lower energy barrier for PLLA nucleation was achieved by trace of LiTFSI because of the enhanced gt conformer contents. This work offers an alternative strategy to enhance PLLA crystallization by small molecules induced conformational pre-ordering.

The miscibility and physical and rheological properties of binary poly(vinylidene fluoride)/maleic anhydride (PVDF/MAH) blends have been systematically investigated. MAH was found to be miscible with PVDF by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Fourier transform infrared (FTIR) investigations provided positive evidence for the specific interaction between the carbonyl groups of MAH and the methylene groups of PVDF. Rheological measurements showed that both the storage modulus and the melt viscosity of PVDF increase with the addition of MAH, followed by a decrease with excess MAH. In addition, the elongation of the PVDF/MAH blend with 10 wt % MAH is 589.7%, which is almost 5 times that of neat PVDF. It is concluded that MAH small molecules act as physical “crosslinking” points for the neighboring PVDF molecule chains due to this specific interaction between PVDF and MAH. Such a physical crosslinking function enhances the storage modulus, viscosity, and mechanical properties of PVDF.