Preferential Control of Forward Reaction Kinetics in Hydrogels Crosslinked with Reversible Conjugate Additions
Preferential Control of Forward Reaction Kinetics in Hydrogels Crosslinked with Reversible Conjugate Additions
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DOI：
10.1021/acs.macromol.0c00335
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发表时间：
2020-05-26
期刊：
影响因子：
5.5
通讯作者：
Rosales, Adrianne M.
中科院分区：
文献类型：
--
作者：
FitzSimons, Thomas M.;Oentoro, Felicia;Rosales, Adrianne M.
使用分子取代来证明通过两种不同的可逆硫杂共轭加成反应对聚乙二醇基水凝胶中的动力学速率常数进行优先控制。共轭受体上强吸电子腈基团的正向速率常数比中性吸电子基团增加了 20 倍，而反向速率常数仅增加了 6 倍。流变实验表明，水凝胶平台模量主要由反应平衡决定，而水凝胶的应力松弛特性则由反向速率常数决定。此外，动态交联使水凝胶能够快速自发地自我修复。这些结果表明，解耦键交换的动力学速率常数可以系统地控制动态共价水凝胶的整体特性，例如它们的适应性、应力松弛能力和自愈特性。
Molecular substitutions were used to demonstrate preferential control over the kinetic rate constants in a poly(ethylene glycol)-based hydrogel with two different reversible thia-conjugate addition reactions. A strong electron-withdrawing nitrile group on the conjugate acceptor showed a 20-fold increase in the forward rate constant over a neutral withdrawing group, whereas the reverse rate constant only increased 6-fold. Rheometry experiments demonstrated that the hydrogel plateau modulus was primarily dictated by reaction equilibrium, whereas the stress relaxation characteristics of the hydrogel were dominated by the reverse rate constant. Furthermore, dynamic crosslinking allowed the hydrogel to rapidly and spontaneously self-heal. These results indicate that decoupling the kinetic rate constants of bond exchange allow systematic control over dynamic covalent hydrogel bulk properties, such as their adaptability, stress relaxation ability, and self-healing properties.