One-Pot Preparation of Autonomously Self-Healable Elastomeric Hydrogel from Boric Acid and Random...

One-Pot Preparation of Autonomously Self-Healable Elastomeric Hydrogel from Boric Acid and Random Copolymer Bearing Hydroxyl Groups
从硼酸和带有羟基的无规共聚物一锅法制备自主可自硬的弹性水凝胶

Self-healable hydrogels based on the dynamically reversible boronate ester or borate ester bonds are usually prepared by reacting boronic acid or boric acid with diol compounds or polymer-like poly(vinyl alcohol) bearing a hydroxyl group in each monomer unit. Herein, we report a finding that not only facilitates the preparation but also extends the range of self-healable hydrogels of this kind. By simply copolymerizing commercially available N,N-dimethylacrylamide and 2-hydroxyethyl acrylate (8:2 weight ratio) in the presence of boric acid in a one-pot fashion, the resulting random copolymer can gel in aqueous solution at pH = 9, giving rise to a solid hydrogel (tensile strength >0.5 MPa at water content of 30%) that, on the one hand, can autonomously self-heal (near 100% fracture stress recovery within 48 h in air at room temperature) and, on the other hand, shows the characteristics of elastomer (little stress relaxation under loading and small residual deformation after unloading upon repeated 300% elongation cycles). The results reveal that it can be sufficient to have a random copolymer with comonomer units bearing hydroxyl groups for reacting with boric acid to generate dynamically reversible borate ester bonds. This finding thus points out a general, facile, and cost-effective method to obtain and explore new borate ester bond-based self-healable hydrogels.
基于动态可逆的硼酸酯或硼酸酯键的可自修复的水凝胶通常通过使硼酸或硼酸与二醇化合物或在每个单体单元中带有羟基的聚合物样聚（乙烯醇）反应来制备。在此，我们报告了一项发现，不仅有助于制备，而且还扩展了这种可自行修复的水凝胶的范围。通过在硼酸存在下以一锅法简单地共聚市售的N，N-二甲基丙烯酰胺和丙烯酸2-羟乙酯（8：2重量比），得到的无规共聚物可以在pH = 9的水溶液中凝胶化，得到上升到固体水凝胶（拉伸强度> 0.5MPa，含水量为30％），一方面可以自动自愈（在室温下空气中48小时内接近100％的断裂应力恢复），并且另一方面，显示了弹性体的特性（在加载时几乎没有应力松弛，在重复300％伸长循环后卸载后的残余变形小）。结果表明，具有带羟基的共聚单体单元的无规共聚物与硼酸反应以产生动态可逆的硼酸酯键就足够了。因此，该发现指出了获得和探索新的基于硼酸酯键的可自愈水凝胶的一般，简便且成本有效的方法。