Graphene-containing thermoresponsive nanocomposite hydrogels of poly(N-isopropylacrylamide) prepared by frontal polymerization

Abstract

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.

Measuring the lateral size of liquid-exfoliated nanosheets with dynamic light scattering

“…[7,9] This process generates large quantities of 2-dimensional nanosheets that are stabilised against aggregation by interactions with the liquid. This can be achieved in certain solvents, [7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] surfactant [25][26][27][28][29][30][31] or polymer solutions [32,33] where the stabilisation mechanisms are enthalpic, electrostatic and steric respectively. [34] Alternatively, both graphene and inorganic layered materials can be exfoliated by lithium intercalation based methods to give nanosheets, [35][36][37] while graphene can be exfoliated and dispersed in liquids as graphene oxide.…”

Liquid Exfoliation of Defect-Free Graphene

“…[36][37][38][39][40][41][42][43][44][45][46][47] This work has contributed greatly to our understanding of the dispersion process, our practical approach to dispersion and the number of solvents available to graphene researchers.…”

Photolatently modulable hydrogels using unilamellar titania nanosheets as photocatalytic crosslinkers

“…Ideally, such hydrogels are dormant under ambient conditions but quickly activated by exposure to light, to enable localized postmodulations. Recently, twodimensional nanosheets [17][18][19][20] have caught special attention as components of hydrogels. In 2002, Haraguchi and Takehisa 17 reported that radical polymerization of vinyl monomers in an aqueous colloidal dispersion of disk-shaped clay nanosheets (Laponite XLG) gives rise to mechanically tough nanocomposite hydrogels.…”