School of Chemical Engineering and Technology, The Key Laboratory of Low-carbon Chemistry & Energy Conservation of Guangdong Province, Sun Yat-sen University, Zhuhai, 519082, China.
School of Pharmacy, Macau University of Science and Technology, Taipa, 999078, Macao.
Mater Horiz. 2023 Mar 6;10(3):993-1004. doi: 10.1039/d2mh01451c.
Bioinspired smart hydrogels with additive-switchable mechanical properties have been attracting increasing attention in recent years. However, most existing hydrogel systems suffer from limited stiffening amplitude and dramatic volume change upon response to environmental triggers. Herein, we propose a novel strategy to prepare additive-responsive hydrogels with ultra-highly adjustable toughness under quasi-isochoric conditions. The key point lies in tuning the softening transition temperature of the hydrogels with non-covalent interactions between the polymer networks and additives, shifting the hydrogels from glassy to rubbery states. As a proof of concept, a variety of glassy hydrogels are prepared and exposed to additives to trigger responsive performances. Young's modulus of the same hydrogel demonstrates up to 36 000 times ultra-broad-range tunability, ranging from 0.0042 to 150 MPa in response to different additives. Meanwhile, negligible volume changes occur, keeping the hydrogels in quasi-isochoric conditions. Interestingly, the mechanical behaviors of the hydrogels manifest remarkable dependence on the additive type and concentration since both the Hofmeister effect and hydrophobicity of the additives play pivotal roles according to mechanism investigations. Furthermore, the regulation with additives reveals satisfactory reversibility and universality. Taken together, this simple and effective approach provides a novel strategy to fabricate hydrogels with highly tunable toughness for versatile applications, including spatially patterned conductive gels and anti-icing coatings.
近年来，具有附加开关力学性能的仿生智能水凝胶受到了越来越多的关注。然而，大多数现有的水凝胶体系在响应环境触发时存在僵硬幅度有限和体积变化剧烈的问题。在此，我们提出了一种新策略，可在准等容条件下制备具有超高可调韧性的添加剂响应水凝胶。关键在于通过聚合物网络与添加剂之间的非共价相互作用来调节水凝胶的软化转变温度，从而将水凝胶从玻璃态转变为橡胶态。作为概念验证，我们制备了各种玻璃态水凝胶并暴露于添加剂以触发响应性能。同一种水凝胶的杨氏模量表现出高达 36000 倍的超宽范围可调性，在响应不同添加剂时可在 0.0042 至 150 MPa 之间变化。同时，体积变化可忽略不计，使水凝胶保持在准等容条件下。有趣的是，根据机理研究，水凝胶的力学行为明显依赖于添加剂的类型和浓度，因为添加剂的Hofmeister 效应和疏水性都起着关键作用。此外，添加剂的调节显示出良好的可重复性和通用性。总之，这种简单有效的方法为制备具有高可调韧性的水凝胶提供了一种新策略，可应用于各种领域，包括空间图案化导电凝胶和防冰涂层。
