Mixtures of poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP) and ionic liquids (IL) are known to form flexible, self-healing, and ion-conductive materials that are often referred to as polymer–gel electrolytes. The ion–dipole interaction occurs between PVDF-HFP and the cation; that is, the IL acts not only as a solvent but also as a transient cross-linker to form the network structure, and the density of the binding site (C–F dipole) along the polymer chain is quite high. While the practical importance of this type of polymer/IL has become evident, the fundamental solution properties of these types of polymers have not been clearly understood. Here, we studied the structure and viscoelastic properties of the PVDF-HFP/IL system using infrared spectroscopy, wide- and small-angle X-ray scattering (WAXS/SAXS), and steady-state and oscillatory shear rheology. The polymer network structure was found to maintain the geometrically similar figure ξ ∼ ϕ^1/3, where ξ and ϕ denote the correlation length (length of the network strand) and volume fraction of the polymer, respectively. In addition, with an increase in ϕ, the larger-scale structure changed from a mass fractal to a surface fractal morphology at the overlap concentration. The dynamics of this polymer network system is presumed to be governed by the relaxation through repeated association–dissociation processes with the cation. The specific viscosity followed η_sp ∼ ϕ⁸ in the concentrated solution of PVDF-HFP. The viscometry results indicated that the apparent binding energy increased with ϕ; that is, the C–F dipoles were cooperatively bound to each other via the cations.

中文翻译：

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离子液体中聚（偏二氟乙烯-co-六氟丙烯）的结构和流变学：溶剂通过离子-偶极相互作用作为弱交联剂

聚（偏二氟乙烯）混合物-hexafluoropropylene) (PVDF-HFP) 和离子液体 (IL) 已知可形成柔性、自愈和离子导电材料，这些材料通常被称为聚合物-凝胶电解质。PVDF-HFP 和阳离子之间发生离子-偶极相互作用；也就是说，IL 不仅充当溶剂，还充当瞬态交联剂以形成网络结构，并且沿聚合物链的结合位点（C-F 偶极子）的密度非常高。虽然这种类型的聚合物/IL 的实际重要性已经变得明显，但这些类型的聚合物的基本溶液性质还没有被清楚地理解。在这里，我们使用红外光谱、广角和小角 X 射线散射 (WAXS/SAXS) 以及稳态和振荡剪切流变学研究了 PVDF-HFP/IL 系统的结构和粘弹性。^1/3，其中 ξ 和 φ 分别表示聚合物的相关长度（网络链的长度）和体积分数。此外，随着 φ 的增加，在重叠浓度下，更大规模的结构从质量分形变为表面分形形态。这种聚合物网络系统的动力学被认为是由通过与阳离子重复的缔合-解离过程的弛豫控制的。在 PVDF-HFP 的浓溶液中，比粘度遵循 η _sp ∼ φ ⁸。粘度测定结果表明，表观结合能随着 φ 的增加而增加；也就是说，C-F 偶极子通过阳离子相互结合。