Liu Shuhui, Gao Guorong, Xiao Ying, Fu Jun
Polymers and Composites Division, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, China.
J Mater Chem B. 2016 May 21;4(19):3239-3246. doi: 10.1039/c6tb00583g. Epub 2016 Apr 20.
Responsive nanocomposite hydrogels are widely recognized as strong and tough soft materials for smart devices, but there are still challenges in their synthesis and in the fabrication of devices. We report here the versatile synthesis of nanocomposite polyelectrolyte hydrogels with high strength and toughness using either cationic or anionic monomers and demonstrate the simple and versatile fabrication of bilayer actuators by assembling the oppositely charged hydrogels through electrostatic attraction. Exfoliated sodium montmorillonite nanosheets were used as cross-linkers through the adsorption of monomers and initiators before in situ free radical polymerization. Nanocomposite hydrogels with negative charges were obtained by the copolymerization of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid, whereas positively charged nanocomposite gels were obtained using acrylamide and dimethylaminoethyl methacrylate methylchloride. The nanocomposite polyelectrolyte hydrogels were responsive to pH and the ionic strength of buffer solutions. They also showed outstanding fatigue resistance against cyclic compression loading and high tensile strength and toughness. The gels were able to recover at room temperature after tensile testing. The oppositely charged hydrogels were assembled with a robust interface based on the electrostatic attraction between the opposite charges. These hydrogels were actuated under an electric field. The oppositely charged hydrogels were assembled into bilayers that were reversibly actuated as a result of the contrasting responsiveness of each gel to the ionic strength.
响应性纳米复合水凝胶被广泛认为是用于智能设备的坚固且坚韧的软材料，但它们在合成及器件制造方面仍存在挑战。我们在此报告了使用阳离子或阴离子单体对具有高强度和韧性的纳米复合聚电解质水凝胶进行通用合成，并展示了通过静电吸引组装带相反电荷的水凝胶来简单且通用地制造双层致动器。在原位自由基聚合之前，通过吸附单体和引发剂，将剥离的钠蒙脱石纳米片用作交联剂。通过丙烯酰胺与2-丙烯酰胺基-2-甲基丙烷磺酸的共聚获得带负电荷的纳米复合水凝胶，而使用丙烯酰胺和甲基氯代甲基丙烯酸二甲氨基乙酯获得带正电荷的纳米复合凝胶。纳米复合聚电解质水凝胶对pH值和缓冲溶液的离子强度有响应。它们还表现出对循环压缩载荷的出色抗疲劳性以及高拉伸强度和韧性。凝胶在拉伸测试后能够在室温下恢复。基于相反电荷之间的静电吸引，带相反电荷的水凝胶以坚固的界面组装在一起。这些水凝胶在电场作用下被驱动。带相反电荷的水凝胶被组装成双层，由于每种凝胶对离子强度的不同响应，双层可被可逆地驱动。
