Entanglement and Relaxation of Poly(methyl methacrylate) Chains in Imidazolium-Based Ionic Liquids with Different Cationic Structures,Macromolecules

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Entanglement and Relaxation of Poly(methyl methacrylate) Chains in Imidazolium-Based Ionic Liquids with Different Cationic Structures
Macromolecules ( IF 5.1 ) Pub Date : 2020-09-09 , DOI: 10.1021/acs.macromol.0c00805
Xi He ₁ , Miqiu Kong ₂ , Yanhua Niu ₁ , Guangxian Li ₁

Affiliation

A series of dicationic ionic liquids (DILs) with two singly charged imidazolium rings linked by different alkyl chain lengths (C₄, C₆, and C₈) were first synthesized. The relaxation and entanglement of poly(methyl methacrylate) (PMMA) chains in both the DILs and conventional monocationic ionic liquids (MILs) with the same anion bis[(trifluoromethyl)sulfonyl]imide ([TFSI]⁻) were investigated by rheological and dynamic light scattering (DLS) measurements. PMMA in DILs exhibits lower critical entanglement concentration, slower relaxation behavior, and a denser entanglement network than in their MIL counterparts, and these differences become more pronounced as the alkyl chain length decreases. The double imidazolium ring structure that provides interaction sites with PMMA chains plays a dominant role in the relaxation and entanglement of the PMMA/DIL system. As a result, the PMMA/DILs show higher modulus, greater viscosity, and better gel recovery than the PMMA/MILs at the same volume fraction. In addition, a stronger dependence on alkyl chain length is also found in PMMA/DILs. With the increase of alkyl chain length, the relaxation of PMMA becomes faster and the entanglement molecular weight increases gradually, indicating the released mobility of polymer chains. Combined with the results of DLS, it is further confirmed that the greater degree of entanglement in PMMA/DILs mainly comes from the contribution of cohesional entanglement in the system.

中文翻译：

聚（甲基丙烯酸甲酯）链在具有不同阳离子结构的咪唑基离子液体中的缠结和弛豫

首先合成了具有两个单电荷的咪唑环的一系列阳离子型离子液体（DIL），两个咪唑环通过不同的烷基链长（C ₄，C ₆和C ₈）连接。聚（甲基丙烯酸甲酯）（PMMA）链在DIL和常规单阳离子离子液体（MIL）中具有相同的阴离子双[（三氟甲基）磺酰基]酰亚胺（[TFSI] ^-）通过流变和动态光散射（DLS）测量进行了研究。DIL中的PMMA与MIL相比，具有更低的临界缠结浓度，较慢的弛豫行为和更紧密的缠结网络，并且随着烷基链长度的减小，这些差异变得更加明显。提供与PMMA链相互作用位点的双咪唑环结构在PMMA / DIL系统的松弛和纠缠中起主要作用。结果，与相同体积分数的PMMA / MIL相比，PMMA / DIL显示出更高的模量，更大的粘度和更好的凝胶回收率。另外，在PMMA / DIL中也发现了对烷基链长度的更强依赖性。随着烷基链长度的增加，PMMA的弛豫变得更快，缠结分子量逐渐增加，表明聚合物链释放的迁移率。结合DLS的结果，进一步证实PMMA / DIL中更大程度的纠缠主要来自系统中内聚纠缠的贡献。

更新日期：2020-09-22

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