Hydrogel nanocomposites as pressure-sensitive adhesives for skin-contact applications

This study investigates the effects of monodisperse polystyrene nanoparticle fillers on the network formation, rheological properties and adhesion performance of hydrogel nanocomposites based on polyacrylamide and poly(acrylamide-hydroxyethyl methacrylate). We demonstrated a simultaneous increase in elasticity and tack of these humid composite materials. A 1H-NMR kinetic study showed quasi-total conversion of these monomers during the polymerization–reticulation process and the formation of inhomogeneities within the hydrogel network structure due to the difference in reactivity ratios of the comonomers: acrylamide (AM) and hydroxyethyl methacrylate (HEMA)(rAM = 0.41 ± 0.01 and rHEMA = 7.4 ± 0.3). The rheological properties of these materials were found to be affected by their chemical composition (HEMA content, presence of nanoparticles and heterogeneities). We investigated the adhesion properties of our materials using a probe test tack. Measurements were carried out on a human skin substitute to compare with metal and investigate the potential use of these hydrogel nanocomposites as dermatological patches. The adhesion energy was found to be related to the chemical composition and rheological properties of the hydrogels, as well as to the surface properties of both the adhesive and the substrate.