利用疏水相互作用合成的水凝胶通常具有较强的力学性能和抗溶胀性能，在软体机器人、3D打印和可穿戴传感器等方面具有极大的应用前景。然而，疏水相互作用的存在会使水凝胶内部高分子链聚集、相互缠结，形成较大的相分离区域，限制至其运动能力。因此，疏水凝胶与基体的黏附往往需要借助其他措施（如溶剂交换、界面化学反应）而很难通过疏水凝胶自身实现有效的黏附。

  近日，中山大学化工学院郭宏磊副教授等通过一步的自由基聚合制备了一种具有高黏附、高强度的疏水型水凝胶。通过在疏水水凝胶内部引入少量的静电相互作用来减小其内部的相分离结构尺寸，赋予凝胶一定的粘弹性。同时,疏水水凝胶本身的高强度和抗溶胀的性质得以保留，而凝胶表面的静电相互作用和疏水缔合的协同作用赋予了凝胶较强的黏附性能。研究表明：在疏水凝胶中引入季铵基团与三聚磷酸根的静电相互作用，不但能够使水凝胶内部相分离区域尺寸减小，提高凝胶材料的力学性能，同时还有利于凝胶内部疏水区域与不同材质的基底（玻璃、有机玻璃、聚丙烯、聚碳酸酯、有机硅树脂、聚四氟乙烯等）发生黏附作用，最大粘附强度达100kPa。复合凝胶的这种强粘附和高韧性特性主要来源于凝胶内部静电相互作用和疏水缔合的协同作用。未来可以利用这种复合结构改善疏水型凝胶材料的粘附和力学性能，为扩大疏水型水凝胶的应用提供重要的指导。

Fig. 1. Schematics of synthesis of a hybrid hydrogel and strong adhesion performance. (a) An illustration of the networks prepared by copolymerization of cationic monomers and hydrophobic monomers in DMSO solution and subsequently swelling in multivalent phosphate salt solution. The multivalent anions serve as physical cross-linking points to attract polycations in the network. (b) Picture of glass surfaces adhered to a 100 g weight of stainless steel by a p(EA-co-DAC)/STPP hydrogel. (c) Adhesion strength of the pEA, pDAC/STPP, and p(EA-co-DAC_10%)/STPP hybrid hydrogels on a glass substrate, the molar fraction of DAC is 10%. (d) Scheme of the strong adhesion of the p(EA-co-DAC)/STPP hydrogel on a glass substrate: both the hydrophobic sites and electrostatic attractions contribute to the strong adhesion.

Fig. 2. (a) Synthesis of the p(EA-co-DAC_10%)/STPP networks, where STPP physically cross-linked with polymer backbones through intermolecular and/or intramolecular interactions. (b) ATR-FTIR spectra of pEA, p(EA-co-DAC_10%) and p(EA-co-DAC_10%)/STPP hydrogels and STPP salt. (c) Donnan potential profile of p(EA-co-DAC_10%)/STPP hydrogel, the reference solution is NaCl solution with a concentration of 10^-5 mol/L. (d) 1D scattering intensity profiles of pEA, p(EA-co-DAC_10%) and p(EA-co-DAC_10%)/STPP hydrogels.

  相关成果以“Modification of Hydrophobic Hydrogels into a Strongly Adhesive and Tough Hydrogel by Electrostatic Interaction” 为题发表在Macromolecules 上。论文通讯作者为中山大学化学工程与技术学院郭宏磊副教授和郭辉副教授。

  原文链接：https://pubs.acs.org/doi/full/10.1021/acs.macromol.1c01115