Lu Mengze, Lian Wei Zhen, Xiao Zhenhua, Liu Lu, Fan Zhiwei, Jin Xiaolin, Jiang Chuanxia, Chen Qian, Tang Zheng-Hai, Yin Panchao, Sun Taolin
South China Advanced Institute for Soft Matter Science and Technology, School of Emergent Soft Matter, South China University of Technology, Guangzhou 510640, China.
Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices, South China University of Technology, Guangzhou 510640, China.
Soft Matter. 2025 Jan 15;21(3):435-447. doi: 10.1039/d4sm01251h.
Understanding the interplay among the mechanical behavior, ionic conductivity and chain dynamics of ionogels is essential for designing flexible conductors that exhibit both high conductivity and excellent mechanical properties. In this study, ionogels were synthesized the radical polymerization of ,'-dimethylacrylamide (DMAA) and methacrylic acid (MAAc) monomers in the presence of ionic liquid 1-ethyl-3-methylimidazolium trifluoromethane sulfonate ([EMIM][OTf]). By varying the mass content of ionic liquid within ionogels, we investigated the mechanical behavior and ionic conductivity at the macroscopic scale using tensile, rheological testing and electrochemical impedance spectroscopy, as well as the dynamic behavior of chain segments and ions within the network at the microscopic scale using broadband dielectric relaxation spectroscopy (BDS) over a broad temperature range. Our findings revealed that variations in ionic liquid concentration significantly affect mechanical performance, ionic conductivity, complex conductivity spectra, and complex permittivity spectra. These ionogels exhibited remarkable stretchability, adhesion, and strain-sensing capabilities. Analysis of BDS indicated that the temperature dependence of the hopping frequency (), the conductivity of free ions (), and the relaxation time () of chain segments conforms to the Vogel-Tammann-Fulcher (VTF) equation for ionogels with varying ionic liquid content. By correlating measured through rheological tests and BDS, we observed a transition from Arrhenius to VTF behavior, which shifts towards lower temperatures with increasing ionic liquid content. This study highlighted a strong coupling between and , as well as between 1/ and , at low ionic concentrations, facilitating high mechanical performance of the ionogels due to viscoelastic energy dissipation. However, as the ionic concentration increased, a slight decoupling of and was noted, leading to a substantial reduction in the mechanical properties of the ionogels. Ultimately, these ionogels demonstrate potential as polymer electrolytes for applications in flexible wearable devices.
了解离子凝胶的机械行为、离子电导率和链动力学之间的相互作用对于设计兼具高导电性和优异机械性能的柔性导体至关重要。在本研究中，通过在离子液体1-乙基-3-甲基咪唑三氟甲磺酸盐（[EMIM][OTf]）存在下使N,N'-二甲基丙烯酰胺（DMAA）和甲基丙烯酸（MAAc）单体进行自由基聚合来合成离子凝胶。通过改变离子凝胶中离子液体的质量含量，我们在宏观尺度上使用拉伸、流变测试和电化学阻抗谱研究了机械行为和离子电导率，以及在微观尺度上在较宽温度范围内使用宽带介电弛豫谱（BDS）研究了网络内链段和离子的动态行为。我们的研究结果表明，离子液体浓度的变化会显著影响机械性能、离子电导率、复电导率谱和复介电常数谱。这些离子凝胶表现出显著的拉伸性、粘附性和应变传感能力。BDS分析表明，对于具有不同离子液体含量的离子凝胶，跳跃频率（ν）、自由离子电导率（σ0）和链段弛豫时间（τ）的温度依赖性符合Vogel-Tammann-Fulcher（VTF）方程。通过关联流变测试和BDS测量的ν，我们观察到从Arrhenius行为到VTF行为的转变，随着离子液体含量的增加，该转变向较低温度移动。本研究强调了在低离子浓度下ν与σ0之间以及1/τ与ν之间的强耦合，由于粘弹性能量耗散，这有助于离子凝胶具有高机械性能。然而，随着离子浓度的增加，注意到ν与σ0之间略有解耦，导致离子凝胶的机械性能大幅降低。最终，这些离子凝胶展示了作为聚合物电解质在柔性可穿戴设备中的应用潜力。
