Stimuli-responsive structure-property switchable polymer materials

The development of polymeric materials with switchable properties upon exposure to external stimuli such as light, heat, force, acids/bases, and chemicals has attracted much attention due to their potential applications in smart coatings, drug carriers, soft robotics, etc. Thus, a systematic understanding of the relationship between the chemical structures and stimuli-responsive properties as well as the corresponding mechanisms of switchable stimuli-responsive polymers is important to guide the sophisticated design of functional macromolecules for specific applications. In this review, we outline the representative chemical structures that enable reversible structural switching to be achieved under photo-, mechano-, CO 2 - and chemo-stimuli, with a brief discussion on thermo- and pH-activation. Polymer materials containing these chemical moieties exhibit unique behaviours on changing their mechanical, thermal or photochemical property in a switchable manner, and their applications in healing materials, rewritable surfaces, drug delivery carriers, conductive hydrogels and luminescent materials are highlighted. Based on the comprehensive summary of structural switchable moieties and applications of polymer materials, this review gives insight into how bottom-up approaches can be used to inspire the future design of switchable multi-stimuli-responsive polymer materials. Typical examples of structural switchable functional groups triggered by photo-, pH-, thermal-, force-, CO 2 - or redox-stimuli for constructing stimuli-responsive polymers.