Stiffness switching hydrogels have been in high demand for intelligent devices, adhesion science, soft robotics, and flexible electronics. However, it is challenging to post-tune the mechanical properties of a hydrogel once the polymer network structure is formed. Inspired by the cononsolvency effect, we prepared a mechanics-switching colloidal hydrogel through the precipitation polymerization of methacrylamide in mixed dimethyl sulfoxide and water solvents. The colloidal network enables the hydrogels to simultaneously strengthen, stiffen, and toughen. The colloidal hydrogels not only display a broad spectrum of adjustable mechanical properties (ranging from 0.08 to 57.1 MPa) via solvent response but also accomplish reversible stiffness conversion through the solvent-tuned conformational adjustment of colloidal polymer networks, with the maximum modulus conversion reaching 1427, and exhibit solvent-responsive shape memory. Based on the stable and tight colloidal network, the hydrogels exhibit antiswelling properties in various aqueous solutions and solvents. The colloidal hydrogel would provide more possibilities in various applications, such as antiimpact protection, shape memory, electronic switches, and intelligent engineering materials. It is envisioned that this work will provide key opportunities in developing mechanics-switching and on-demand tuning of soft materials for tissue engineering, flexible electronics, and biomedical science.

中文翻译：

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受 Cononsolvency 效应启发的力学可切换和抗溶胀胶体水凝胶


刚度切换水凝胶在智能设备、粘附科学、软机器人和柔性电子产品中的需求量很大。然而，一旦聚合物网络结构形成，对水凝胶的机械性能进行后调整就具有挑战性。受溶解效应的启发，我们通过甲基丙烯酰胺在混合二甲基亚砜和水溶剂中的沉淀聚合制备了一种力学切换胶体水凝胶。胶体网络使水凝胶能够同时增强、变硬和增韧。胶体水凝胶不仅通过溶剂响应显示出广泛的可调机械性能（范围从 0.08 到 57.1 MPa），而且还通过胶体聚合物网络的溶剂调谐构象调整实现可逆刚度转换，最大模量转换达到 1427，并表现出溶剂响应的形状记忆。基于稳定紧密的胶体网络，水凝胶在各种水溶液和溶剂中表现出抗溶胀性能。胶体水凝胶将为各种应用提供更多可能性，例如抗冲击保护、形状记忆、电子开关和智能工程材料。预计这项工作将为开发用于组织工程、柔性电子和生物医学科学的软材料的力学切换和按需调整提供关键机会。