In the present work, the use of a commercial ionic liquid as a convenient solvent medium for graphite exfoliation in mild and easy conditions without any chemical modification is presented. To confirm the presence of few layer graphene, its dispersion, which exhibits Tyndall effect, was characterized by Raman and UV spectroscopies, and atomic force and field emission electron microscopies. It is noteworthy that, by gravimetric analysis, a graphene concentration as high as 5.33 mg ml À1 was determined, which is the highest value reported so far in any solvent.

Frontal polymerization has been successfully used to synthesize poly(N-isopropylacrylamide) nanocomposite hydrogels containing graphene. The latter was directly achieved by ultrasound treatment of a dispersion of graphite in N-methylpyrrolidone. The dispersion, having the concentration of 2.21 g L À1 , was characterized by TEM analysis and mixed with suitable amounts of N-isopropylacrylamide for the synthesis of graphene-containing nanocomposite polymer hydrogels. The nanocomposite hydrogels were analyzed by SEM and Raman spectroscopy, and their swelling and rheological properties were investigated. It was found that graphene strongly influences the swelling ratio, dramatically increasing it, even if present in small amounts. Finally, the rheological properties of the hydrogels were correlated with the graphene content: G 0 modulus and complex viscosity were found to increase with increasing nanofiller concentration, thus indicating the occurrence of good interactions between the two phases. Nevertheless, at a high concentration (i.e., 0.13 wt.%), graphene showed a lubrication effect, lowering the rheological parameters and approaching the same pseudoplastic behaviour of the unfilled material.

Frontal polymerization was used as an alternative method for the easy and fast preparation of polymer hydrogels prepared from N-isopropylacrylamide (NIPAAm) and N-vinylcaprolactam (VCL), the latter being less toxic and less expensive than NIPAAm. All samples were characterized in terms of their swelling behavior, and their thermal properties were investigated by DSC. It was found that VCL influences both pore size and shape distribution. Moreover, also the swelling ratio of the materials is dependent on the monomer ratio. Eventually, by a comparison with analogous samples prepared by the classical polymerization technique, it was found that the two methods give rise to hydrogels characterized by very diverse swelling capability; furthermore, swelling reversibility was also found to be different when temperature is allowed to cyclically vary between values that are below and above the lower critical solution temperature. In particular, samples prepared by frontal polymerization are characterized by lower swelling ratio and larger swelling recovery capability.