Takahashi Tomohiro, Karasawa Naoya, Sano Koki
Department of Chemistry and Materials, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano, 386-8567, Japan.
Adv Mater. 2025 Jul 9:e2505268. doi: 10.1002/adma.202505268.
Anisotropic hydrogels with designable structural complexity can exhibit sophisticated properties reminiscent of those found in living organisms. However, conventional synthetic methods typically require specific anisotropic additives and complicated processes, limiting design flexibility. Here, a simple and versatile strategy to synthesize anisotropic hydrogels with photo-designable orientations of polymer networks is developed by harnessing a "gel-gel interface," which can be generated through the intentional adhesion between hydrogels. This strategy originates from the serendipitous discovery: when a gel-gel interface is intentionally introduced into a hydrogel through a two-step polymerization, the polymer networks near the interface are spontaneously aligned perpendicular to the interface, as a result of the simultaneous swelling and fixation process during gel-to-gel adhesion. By employing a photo-initiator system to control the gel-gel interface, anisotropic hydrogels with both 2D and 3D designed polymer orientations, as well as anisotropic hydrogels with thermally switchable polymer orientations, are successfully synthesized. The gel-gel interface has long been regarded as merely an undesirable byproduct of gel adhesion, while the complementary bulk region of hydrogels has been the primary focus in constructing anisotropic hydrogels. In contrast, this work demonstrates the utility of the gel-gel interface, expanding design possibilities for next-generation hydrogels with designable structural complexity.
具有可设计结构复杂性的各向异性水凝胶能够展现出类似于生物体中发现的复杂特性。然而，传统的合成方法通常需要特定的各向异性添加剂和复杂的工艺，这限制了设计的灵活性。在此，通过利用“凝胶-凝胶界面”，开发出一种简单且通用的策略来合成具有可光设计聚合物网络取向的各向异性水凝胶，该界面可通过水凝胶之间的有意粘附产生。这一策略源于一个意外发现：当通过两步聚合将凝胶-凝胶界面有意引入水凝胶中时，由于凝胶与凝胶粘附过程中的同时溶胀和固定过程，界面附近的聚合物网络会自发地垂直于界面排列。通过采用光引发剂体系来控制凝胶-凝胶界面，成功合成了具有二维和三维设计聚合物取向的各向异性水凝胶，以及具有热开关聚合物取向的各向异性水凝胶。凝胶-凝胶界面长期以来一直仅被视为凝胶粘附的不良副产物，而水凝胶的互补本体区域一直是构建各向异性水凝胶的主要关注点。相比之下，这项工作展示了凝胶-凝胶界面的实用性，为具有可设计结构复杂性的下一代水凝胶拓展了设计可能性。
