School of Engineering and Applied Sciences, Kavli Institute for Bionano Science and Technology, Harvard University, MA, 02138, USA.
State Key Laboratory of Fluid Power and Mechatronic System, Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Department of Engineering Mechanics, and Center for X-Mechanics, Zhejiang University, Hangzhou, Zhejiang, 310027, P. R. China.
Adv Mater. 2019 Sep;31(39):e1903062. doi: 10.1002/adma.201903062. Epub 2019 Aug 4.
For a hydrogel coating on a substrate to be stable, covalent bonds polymerize monomer units into polymer chains, crosslink the polymer chains into a polymer network, and interlink the polymer network to the substrate. The three processes-polymerization, crosslinking, and interlinking-usually concur. This concurrency hinders widespread applications of hydrogel coatings. Here a principle is described to create hydrogel paints that decouple polymerization from crosslinking and interlinking. Like a common paint, a hydrogel paint divides the labor between the paint maker and the paint user. The paint maker formulates the hydrogel paint by copolymerizing monomer units and coupling agents into polymer chains, but does not crosslink them. The paint user applies the paint on various materials (elastomer, plastic, glass, ceramic, or metal), and by various operations (brush, cast, dip, spin, or spray). During cure, the coupling agents crosslink the polymer chains into a network and interlink the polymer network to the substrate. As an example, hydrogels with thickness in the range of 2-20 µm are dip coated on medical nitinol wires. The coated wires reduce friction by eightfold, and remain stable over 50 test cycles. Also demonstrated are several proof-of-concept applications, including stimuli-responsive structures and antifouling model boats.
为了使水凝胶涂层在基底上稳定，共价键将单体单元聚合成长链聚合物，将聚合物链交联成聚合物网络，并将聚合物网络与基底连接。这三个过程——聚合、交联和连接——通常是同时发生的。这种同时性阻碍了水凝胶涂层的广泛应用。这里描述了一种创建水凝胶涂料的原理，该原理将聚合与交联和连接分离。就像普通涂料一样，水凝胶涂料将涂料制造者和涂料使用者的工作分开。涂料制造者通过共聚单体单元和偶联剂将其连接成聚合物链，但不交联它们。涂料使用者将涂料应用于各种材料（弹性体、塑料、玻璃、陶瓷或金属），并通过各种操作（刷涂、浇铸、浸涂、旋转或喷涂）。在固化过程中，偶联剂将聚合物链交联成网络，并将聚合物网络与基底连接。例如，厚度在 2-20 µm 范围内的水凝胶通过浸涂涂覆在医用镍钛诺丝上。涂覆的金属丝将摩擦力降低了八倍，并且在 50 次测试循环中保持稳定。还展示了几个概念验证应用，包括刺激响应结构和防污模型船。
