Key Laboratory of Colloid and Interface Chemistry, Shandong University, Ministry of Education, Jinan, 250100, P. R. China.
Soft Matter. 2018 May 30;14(21):4327-4334. doi: 10.1039/c8sm00504d.
Stimuli-responsive or "smart" soft materials have raised considerable attention due to their ability to spontaneously respond to external environmental variations and have a great potential for wide applications. Herein, a thermo/redox responsive hydrogel is facilely constructed based on a dual crosslinked matrix: the primary chemical crosslinked copolymer is composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and poly(ionic liquid), and the secondary physical crosslinking component is generated by the ionic coordination between iron ions and carboxyl groups in the poly(ionic liquid). The non-covalent ion coordination crosslinking is introduced into a covalently crosslinked network, which further strengthens the soft PNIPAM matrix and enhances the mechanical performances of the hydrogels. The excellent thermosensitivity of PNIPAM and the good conductive property of poly(ionic liquid) provide the hydrogel with an attractive performance as a thermo-responsive switch. Moreover, the trapped iron ions in the network endow the hydrogels with redox-responsiveness, which could be reversibly chemically oxidized and reduced. The mechanical strength of hydrogels could also be tuned by the crosslinked capacity of iron ions within the gel matrix between the strong binding of the oxidized state (Fe3+) and poor coordination of the reduced state (Fe2+). These stimuli-responsive hydrogels have the potential to be used as smart materials for stimuli-responsive devices.
刺激响应或“智能”软材料因其能够自发响应外部环境变化而受到广泛关注，具有广泛的应用潜力。本文通过双交联基质构建了一种热/氧化还原响应水凝胶：主化学交联共聚物由温度响应性聚（N-异丙基丙烯酰胺）（PNIPAM）和聚离子液体组成，二次物理交联组分由离子在聚离子液体中的配位产生。非共价离子配位交联引入到共价交联网络中，进一步增强了柔软的 PNIPAM 基质，并提高了水凝胶的机械性能。PNIPAM 的优异温敏性和聚离子液体的良好导电性为水凝胶作为热响应开关提供了有吸引力的性能。此外，网络中捕获的铁离子赋予水凝胶氧化还原响应性，其可以被可逆地化学氧化和还原。通过凝胶基质中铁离子的交联能力进行机械强度的调节，在氧化状态（Fe3+）的强结合和还原状态（Fe2+）的差配位之间。这些刺激响应性水凝胶有望用作刺激响应器件的智能材料。
