Enhanced mechanical properties and self-healing behavior of PNIPAM nanocomposite hydrogel by using POSS as a physical crosslinker

In this study, water-soluble octa(3-chloroammoniumpropyl) silsesquioxane (OCAPS) was found to aggregate into nanoparticles with a positive charge in solution, which can attract persulfate anion radical to initiate N-isopropylacrylamide monomers. Due to the electrostatic and hydrogen bond interaction between OCAPS and poly(N-isopropylacrylamide) (PNIPAM) chain, OCAPS can act as an effective physical crosslinker to result in a nanocomposite hydrogel (OCAPS-PNIPAM) with very small loading N, N′-methylene-bisacrylamide (50–100 ppm). The incorporation of OCAPS increases the crosslinking degree of the PNIPAM hydrogel and decreases the swelling ratio in deionized water. The mechanical properties of OCAPS-PNIPAM hydrogel were enhanced greatly by the presence of OCAPS and can be adjusted by the feed ratio. The compression and elasticity moduli vary from 3.52 to 7.59 kPa and 7.67 to 33.91 kPa, respectively. The tensile strength ranges from 6.82 to 243.41 kPa with fracture energy between 503.5 and 4781.7 J·m −2 . Rheological measurements suggest that OCAPS-PNIPAM hydrogels have stable networks and the loss factor decreases as increasing OCAPS content. OCAPS-PNIPAM hydrogels also can self-heal under certain conditions with low crosslinker loading. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48486.