Institute for Chemical Reaction Design and Discovery (ICReDD), Hokkaido University, Sapporo 001-0021, Japan.
Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China.
Proc Natl Acad Sci U S A. 2022 Sep 6;119(36):e2207422119. doi: 10.1073/pnas.2207422119. Epub 2022 Aug 29.
Understanding the physical principle that governs the stimuli-induced swelling and shrinking kinetics of hydrogels is indispensable for their applications. Here, we show that the shrinking and swelling kinetics of self-healing hydrogels could be intrinsically asymmetric. The structure frustration, formed by the large difference in the heat and solvent diffusions, remarkably slows down the shrinking kinetics. The plateau modulus of viscoelastic gels is found to be a key parameter governing the formation of structure frustration and, in turn, the asymmetric swelling and shrinking kinetics. This work provides fundamental understandings on the temperature-triggered transient structure formation in self-healing hydrogels. Our findings will find broad use in diverse applications of self-healing hydrogels, where cooperative diffusion of water and gel network is involved. Our findings should also give insight into the molecular diffusion in biological systems that possess macromolecular crowding environments similar to self-healing hydrogels.
理解水凝胶刺激诱导的溶胀和收缩动力学的物理原理对于它们的应用是必不可少的。在这里，我们表明自修复水凝胶的溶胀和收缩动力学可能是内在不对称的。由热和溶剂扩散的巨大差异形成的结构受挫显著减缓了收缩动力学。发现粘弹性凝胶的平台模量是控制结构受挫形成的关键参数，进而控制不对称的溶胀和收缩动力学。这项工作为自修复水凝胶中温度触发的瞬态结构形成提供了基本的认识。我们的发现将广泛应用于涉及水和凝胶网络协同扩散的自修复水凝胶的各种应用中。我们的发现还应该深入了解具有类似于自修复水凝胶的高分子拥挤环境的生物系统中的分子扩散。
