College of Civil Engineering, Nanjing Tech University, Nanjing 211816, China.
School of Engineering, RMIT University, Melbourne, 3083, Australia.
Soft Matter. 2023 Mar 8;19(10):1913-1929. doi: 10.1039/d3sm00039g.
The incorporation of room temperature ionic liquids (ILs) into dielectric elastomer composites is currently generating great interest due to their potential applications in soft actuators and optical-related devices. Experiments have shown that the electrical properties of IL enhanced soft composites (ILESCs) are dependent on AC (alternating current) frequency of the electrical loading. This current work helps develop a mixed micromechanical model with the incorporation of an electric double layer (EDL) to predict the electrical properties of the ILESCs while revealing the physical mechanisms (including crowding and overscreening structures, percolation thresholds, interfacial tunneling, Maxwell-Wagner-Sillars polarization) that underpin the phenomena. Particularly, Bazant-Storey-Kornyshev (BSK) phenomenological theory is integrated into the EDL surface diffusion model for the first time to evaluate the influence of crowding and overscreening effects. The results show excellent agreement with experimental data of IL enhanced PDMS composites over the frequency range from 1 Hz to 10 GHz. Parametric analysis from the perspective of designing is conducted to explore the methods for optimization of ILESCs with high dielectric constants and frequency-dependent stability. It is found that an IL with a smaller size and aspect ratio increases the dielectric constant of the ILESCs more significantly below the interface relaxation frequency. Increasing the surface charge density of the matrix and using ILs delay the frequency-facilitated dielectric response, which is beneficial to maintain the dielectric stability of the ILESCs.
室温离子液体（ILs）的掺入使得介电弹性体复合材料在软致动器和光相关器件等领域的潜在应用受到了广泛关注。实验表明，IL 增强软复合材料（ILESCs）的电性能取决于外加交流（AC）电流的频率。目前的工作有助于开发一种混合细观力学模型，该模型将电双层（EDL）纳入其中，以预测 ILESCs 的电性能，同时揭示支撑这一现象的物理机制（包括拥挤和过屏蔽结构、渗流阈值、界面隧道、Maxwell-Wagner-Sillars 极化）。特别地，首次将 Bazant-Storey-Kornyshev（BSK）唯象理论集成到 EDL 表面扩散模型中，以评估拥挤和过屏蔽效应的影响。结果表明，在 1 Hz 至 10 GHz 的频率范围内，与 IL 增强 PDMS 复合材料的实验数据具有很好的一致性。从设计的角度进行了参数分析，以探讨优化具有高介电常数和频率相关稳定性的 ILESCs 的方法。结果发现，较小尺寸和纵横比的 IL 在界面弛豫频率以下更显著地提高了 ILESCs 的介电常数。增加基体的表面电荷密度并使用 IL 会延迟频率促进的介电响应，这有利于保持 ILESCs 的介电稳定性。
