Poly(N-isopropylacrylamide)-based smart hydrogels: Design, properties and applications

Development of polymer-based smart materials, which can autonomously alter their physical and/or chemical properties when exposed to external stimuli, is a thriving research frontier in contemporary advanced functional materials science. Poly(N-isopropylacrylamide) (PNIPAM)-based smart hydrogels are known to exhibit distinct thermo-responsive properties near a lower critical solution temperature (LCST), which have found diverse promising applications such as smart coating, drug delivery, tissue regeneration, and artificial muscles. In this review, we provide an up-to-date account on the recent developments in advanced functional PNIPAM-based smart hydrogels and their emerging technological applications in the fields of smart actuators, photonic crystals, smart windows and novel biomedical applications. The fundamental design and synthetic strategies of PNIPAM-based smart hydrogels are discussed. Their unique properties, underlying mechanisms and potential applications in different fields are highlighted. Finally, this review provides a brief conclusion and enumerates the challenges and opportunities in this rising area of research and development involving these intriguing polymer-based advanced smart systems rooted in chemistry and materials science. It is expected that this review would provide significant insights for the development of reconfigurable and programmable advanced smart materials with numerous possibilities, prompting the rapid advancement of this highly interdisciplinary area, which encompasses materials science, polymer science, synthetic chemistry, device engineering, physics, biology, nanoscience and nanotechnology.