Collins Joe, Nadgorny Milena, Xiao Zeyun, Connal Luke A
The Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, Victoria, 3010, Australia.
Macromol Rapid Commun. 2017 Mar;38(6). doi: 10.1002/marc.201600760. Epub 2017 Jan 24.
The dynamic covalent characteristics of oxime and boronate ester bonds have been explored. A small excess of a competing aldehyde under acidic conditions resulted in oxime polymer degradation from high molecular weights (30 kDa) to low molecular weight oligomers (2.2 kDa). The dynamic nature of oxime bonds imparts oxime cross-linked hydrogels with self-healing properties and the incorporation of phenyl boronic acid groups into the hydrogel network provides a platform for hydrogel functionalization. The addition of a polyphenol (tannic acid) proves a facile means to incorporate a second, dynamic covalent cross-linking network through boronate ester formation which, owing to the increase in the degree of cross-linking, is found to be nearly double the hydrogel strength (storage modulus increased from 4.6 to 8.5 kPa). Finally, the tannic acid cross-linking network is selectively degraded returning the hydrogel storage modulus to its initial value and providing a means for the synthesis of materials with tunable mechanical properties.
肟键和硼酸酯键的动态共价特性已经得到了研究。在酸性条件下，少量过量的竞争性醛会导致肟聚合物从高分子量（30 kDa）降解为低分子量低聚物（2.2 kDa）。肟键的动态性质赋予了肟交联水凝胶自愈特性，并且将苯基硼酸基团引入水凝胶网络为水凝胶功能化提供了一个平台。添加一种多酚（单宁酸）被证明是一种通过硼酸酯形成引入第二个动态共价交联网络的简便方法，由于交联度的增加，发现水凝胶强度几乎翻倍（储能模量从4.6 kPa增加到8.5 kPa）。最后，单宁酸交联网络被选择性降解，使水凝胶储能模量恢复到其初始值，并为合成具有可调机械性能的材料提供了一种方法。
