Michael Charalambos, Apostolides Demetris E, Patrickios Costas S, Sakai Takamasa
Department of Chemistry, University of Cyprus, 1 University Avenue, Aglanjia, 2109 Nicosia, Cyprus.
Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Soft Matter. 2022 Aug 17;18(32):5966-5978. doi: 10.1039/d2sm00594h.
Well-defined dually dynamic hydrogels were prepared by end-linking four-armed poly(ethylene glycol) stars (tetraPEG stars) through two different types of dynamic covalent cross-links, boronates and acylhydrazones, leading to robust, self-healable materials. This required the prior end-functionalization of tetraPEG stars, originally bearing four hydroxyl terminal groups, with glucoronate, acylhydrazide and benzaldehyde groups, resulting in three differently end-functional star polymers. A first type of dually dynamic hydrogel resulted from the combination of the first two differently end-functionalized tetraPEG stars, cross-linked by 4-formylphenyl boronic acid, a small molecule bearing both an aldehyde and a boronic acid group, respectively complementary to the acylhydrazide and glucoronate end-groups of the two above-mentioned tetraPEG stars. For comparison, a singly-dynamic hydrogel cross-linked with only acylhydrazone groups was also prepared, as well as a double-like hydrogel combining the constituents of both of the above-mentioned hydrogels. All three types of hydrogels were prepared at three different pH values, 8.5, 10.5 and 12.5, leading to a total number of nine samples. All nine samples were investigated for their self-healing, mechanical, viscoelastic and aqueous swelling/degradation properties. This study sets the basis for the development of well-defined polymeric dynamic covalent hydrogels where their self-healing and stability can be readily tuned.
通过两种不同类型的动态共价交联（硼酸酯和酰腙）将四臂聚乙二醇星型聚合物（tetraPEG星型聚合物）进行端基连接，制备出了结构明确的双动态水凝胶，从而得到了坚固且可自愈的材料。这需要对最初带有四个羟基端基的tetraPEG星型聚合物预先用葡萄糖醛酸酯、酰肼和苯甲醛基团进行端基功能化，从而得到三种不同端基功能化的星型聚合物。第一种双动态水凝胶是由前两种不同端基功能化的tetraPEG星型聚合物组合而成，通过4-甲酰基苯基硼酸进行交联，4-甲酰基苯基硼酸是一种分别与上述两种tetraPEG星型聚合物的酰肼和葡萄糖醛酸酯端基互补的同时带有醛基和硼酸基团的小分子。作为对比，还制备了仅用酰腙基团交联的单动态水凝胶，以及一种结合了上述两种水凝胶成分的类双水凝胶。所有三种类型的水凝胶均在8.5、10.5和12.5这三个不同的pH值下制备，共得到九个样品。对所有九个样品的自愈性、机械性能、粘弹性和水溶胀/降解性能进行了研究。该研究为开发结构明确的聚合物动态共价水凝胶奠定了基础，在这种水凝胶中，其自愈性和稳定性可以很容易地进行调节。
