Responsive materials based on coordination bonds

Abstract

Responsive materials can respond to different external stimuli by changing their chemical or/and physical properties, thus being useful for various applications such as drug delivery, bioimaging, actuators, and sensors. A common strategy for constructing responsive materials is to introduce dynamic covalent bonds or noncovalent interactions into polymer systems. Compared with noncovalent interactions and other covalent bonds, coordination bonds have the peculiarity that their bond strength and dissociation rate can be tuned to a greater extent. Such tunability makes coordination bonds uniquely advantageous in constructing stimuli‐responsive materials. Herein, we summarize the recent progress of responsive materials based on coordination bonds that are classified into seven categories, that is, thermo‐responsive, photo‐responsive, electro‐responsive, mechano‐responsive, chemo‐responsive, pH‐responsive, and other responsive materials, according to the type of external stimuli. The corresponding mechanism, design strategy, and research status of each category are comprehensively summarized. Finally, the prospects and challenges for the development of stimuli‐responsive materials based on coordination bonds are discussed.

Stimuli responsive actuators: recent advances

“…These include high capacitance, impressive electrical and thermal conductivity, excellent electro-magnetic wave absorption, hydrophilicity, mechanical stability and notable dispersibility in various polar solvents. 9–14 MXenes also exhibit superior light absorption across a wide wavelength range of 300–1300 nm, with reported photo-thermal conversion efficiency up to 100%. 15,16 Additionally, the thermal expansion effect and the ability to undergo reversible volume changes make MXenes advantageous for application in photo-thermal responsive actuators.…”