Li Yongqiang, Chen Liufang, Li Chuanfu, Lin Lin, Yan Zhibo, Liu Junming
Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
Department of Applied Physics, College of Science, Nanjing Forestry University, Nanjing 210037, China.
Gels. 2022 Jun 28;8(7):409. doi: 10.3390/gels8070409.
Hydrogels are composed of a three-dimensional network of cross-linked hydrophilic polymer chains and large amounts of water. The physicochemical properties of the polymer-water interface in hydrogels draw our attention. Due to the complex structure of hydrogel systems, it is still a challenge to investigate the interfacial layer properties of hydrogels through experiments. In this work, we investigate the properties of the covalently bonded chitosan-based ice-hydrogels interfacial layer by dielectric relaxation spectroscopy (DRS) techniques in the presence of avoided electrode polarization. The DRS data exhibit that the polymer-water interfacial layer has a strong dielectric signal response, which indicates that a large number of polar electric dipoles or polar molecules may be contained in the interfacial layer. The variable temperature dielectric relaxation behavior of a series of chitosan-base ice-hydrogels showed that the value of dielectric activation energy for different water contents is about 180 kJ/mol, which is much larger than that of the polymer and ice phases, suggesting a strong coupling of polar electric dipoles within the interfacial layer. This work demonstrates the important role of the polymer-water interface in covalently bonded hydrogels, which will provide assistance in the design and application of covalently bonded hydrogels.
水凝胶由交联的亲水性聚合物链和大量水组成的三维网络构成。水凝胶中聚合物 - 水界面的物理化学性质引起了我们的关注。由于水凝胶体系结构复杂，通过实验研究水凝胶的界面层性质仍然是一项挑战。在这项工作中，我们在避免电极极化的情况下，通过介电弛豫光谱（DRS）技术研究了共价键合的壳聚糖基冰 - 水凝胶界面层的性质。DRS数据表明，聚合物 - 水界面层具有强烈的介电信号响应，这表明界面层中可能包含大量极性电偶极或极性分子。一系列壳聚糖基冰 - 水凝胶的变温介电弛豫行为表明，不同含水量的介电活化能值约为180 kJ/mol，这远大于聚合物和冰相的介电活化能值，表明界面层内极性电偶极存在强耦合。这项工作证明了聚合物 - 水界面在共价键合水凝胶中的重要作用，这将为共价键合水凝胶 的设计和应用提供帮助。
