Rheological Scaling of Ionic Liquid-Based Polyelectrolytes in the Semidilute Unentangled Regime from Low to High Salt Concentrations
Rheological Scaling of Ionic Liquid-Based Polyelectrolytes in the Semidilute Unentangled Regime from Low to High Salt Concentrations
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DOI：
10.1021/acs.macromol.1c00576
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发表时间：
2021-06
期刊：
影响因子：
5.5
通讯作者：
A. Matsumoto;Ryota Yoshizawa;O. Urakawa;Tadashi Inoue;A. Shen
中科院分区：
文献类型：
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作者：
A. Matsumoto;Ryota Yoshizawa;O. Urakawa;Tadashi Inoue;A. Shen
聚合离子液体（PILs）是一类具有离子液体结构的特殊含离子聚合物。PILs在离子液体溶液中的粘弹性预计会受到聚合物 - 聚合物相互作用以及离子液体离子的电荷屏蔽的影响，在高离子液体浓度下，由于强烈的离子相关性，这种影响变得复杂。在这项工作中，我们旨在了解在具有中等聚合物 - 聚合物相互作用的半稀无缠结（SU）聚合物体系中，离子相关性对PIL在离子液体溶液中的剪切流变学的影响。我们对一种PIL，即聚（1 - 丁基 - 3 - 乙烯基咪唑鎓双（三氟甲磺酰）亚胺），在一种离子液体（1 - 丁基 - 3 - 甲基咪唑鎓双（三氟甲磺酰）亚胺）和一种非离子溶剂（二甲基甲酰胺）的混合物中进行了系统的流变学表征，以在固定的聚合物浓度下，评估随着离子液体浓度\(c_{IL}\)变化的比粘度\(\eta_{sp}\)和最长松弛时间\(\lambda\)。我们发现，在低盐浓度区域的聚电解质溶液的标度理论下，\(\eta_{sp}\)和\(\lambda\)最初都随着\(c_{IL}\)的增加而降低。然而，这些值在高\(c_{IL}\)时出现上升。我们通过提出一种针对SU溶液的电荷屏蔽模型来解释观察到的非单调粘弹性行为，该模型考虑了浓离子液体溶液中修正的屏蔽长度以及完全电荷屏蔽。我们的结果展示了在存在中等聚合物 - 聚合物相互作用的情况下，浓离子液体溶液中的强离子相关性如何改变PILs的静电性质及其相应的粘弹性。
Polymerized ionic liquids (PILs) are a special class of ion-containing polymers with ionic liquid structures. The viscoelastic properties of PILs in IL solutions are expected to be influenced by both polymer−polymer interaction and charge screening by IL ions, which becomes complex at high IL concentrations due to strong ionic correlations. In this work, we aim to understand the effect of the ionic correlations on the shear rheology of PIL in IL solutions in the semidilute unentangled (SU) polymer regime, with moderate polymer−polymer interactions. We conducted systematic rheological characterization of a PIL, poly(1butyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide), in a mixture of an IL, 1-butyl-3-methyl imidazol ium bis(trifluoromethanesulfonyl)imide, and a non-ionic solvent, dimethylformamide, to evaluate the specific viscosity ηsp and the longest relaxation time λ with varying IL concentrations cIL, at a fixed polymer concentration. We found that both ηsp and λ initially decreased with the increasing cIL, following the scaling theory of polyelectrolyte solutions in the low salt concentration regime. However, these values exhibited an upturn at high cIL. We explained the observed non-monotonic viscoelastic behavior by proposing a charge screening model for SU solutions, accounting for both modified screening length in concentrated IL solutions and complete charge screening. Our results demonstrate how the strong ionic correlation in concentrated IL solutions modifies the electrostatics of PILs and their corresponding viscoelastic properties in the presence of moderate polymer−polymer interactions.