Persistently reversible pH-/thermo-responsive chitosan/poly (N-isopropyl acrylamide) hydrogel through clickable crosslinked interpenetrating network

Abstract

Hydrogels with multi-stimuli responsiveness were variously developed to enable advanced applications. Although the durability under swelling/shrinking reversibility and repeatability are also needed, the plausible fabrication processes were still under investigation. The present work proposes a simple approach to achieve persistently reversible multi-responsive hydrogels by crosslinking the two responsive interpenetrating networks (IPNs), so-called crosslinked network IPN (CN-IPNs). The combination of two responsive hydrogels, i.e., pH-responsive chitosan (CS) crosslinked with diacid, and thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) crosslinked with divinyl, is a good model for CN-IPNs. The further crosslinking of both networks via thiol-ene Click results in CS/PNIPAM in the form of CN-IPNs hydrogel. The hydrogel obtained expresses the persistently reversible pH-/thermo-responsiveness as evidenced from the maintaining appearances and the dimensional stability including the mechanical strength even after several pH and thermal treatment cycles. The CN-IPNs fabrication is ease and practical for stimuli-responsive polymers which the persistent swelling/shrinkage reversibility brings in the long-lasting performances for the advanced bio-related applications, especially artificial muscles, etc.