A facile method for reinforcing poly( N ‐isopropylacrylamide)‐hectorite clay nanocomposite hydrogels by heat treatment

A facile method was explored to reinforce the poly( N ‐isopropylacrylamide) (PNIPAm)‐hectorite nanocomposite hydrogel (NC gel) by heat treatment at temperature above the volume phase transition temperature (VPTT), which enhanced mechanical strength and reduced swelling capacity with denser microporous structure as compared with the non‐treated NC gel. This reinforcement effect was increased by increasing treating temperature and/or treating time, which still remained even after swelling, indicating an irreversible structure change in the treated NC gels. Heat treatment became more effective when the NC gel contained higher clay content. The quartz crystal microbalance (QCM) data showed that the interaction between PNIPAm chains and clay platelets became stronger at temperatures higher than the VPTT, causing an increase in the crosslinking density of the treated NC gels. A strong hydrogel was obtained by heat treatment of the aqueous mixture of PNIPAm and hectorite clay for the first time. POLYM. COMPOS., 37:1557–1563, 2016. © 2014 Society of Plastics Engineers