Graphene derivatives in responsive hydrogels: Effect of concentration and surface chemistry

Abstract

Reduced graphene oxide (RGO) containing composite hydrogels, based on poly(Nisopropylacrylamide) (PNIPA) were prepared by two different methods: i) by incorporating RGO directly into the polymer matrix; ii) applying a post-synthesis reduction of the grapheneoxide (GO) already incorporated into the polymer. The samples were compared by various microscopic (small angle neutron scattering, differential scanning calorimetry, 1 H NMR spectroscopy, thermogravimetry) and macroscopic (kinetic and equilibrium swelling properties and mechanical testing) techniques. Results from microscopic and macroscopic measurements show that the dispersity of the nanoparticles as well as their interaction with the polymer chains are influenced by their surface chemistry. Incorporation of nanoparticles limits the shrinkage and slows down the kinetics of the thermal response. Both thermogravimetric and solid-state 1 H NMR measurements confirmed strong polymernanoparticle interaction when hydrophilic GO was used in the synthesis. In these cases, the slow thermal response may be explained by the decrease of the free volume inside the nanocomposite matrix caused by a hypernodal structure. Our results imply that both the chemistry and the concentration of incorporated graphene derivatives are promising in tuning the thermal responsivity of PNIPA.

Poly(N-isopropylacrylamide)-Based Thermoresponsive Composite Hydrogels for Biomedical Applications

“…First, they can mechanically reinforce the hydrogel network and tune the elasticity of the hydrogel. For example, two-dimensional GO nanosheets [65,68,[72][73][74] or nano-clays [35,70] have been incorporated within PNIPAM hydrogels, thereby effectively modulating their mechanical properties. In the work of Berke et al [72], GO platelets were incorporated into the PNIPAM network by using chain nucleation, which resulted in a hypernodal structure of the PNIPAM gel ( Figure 1).…”

“…Superparamagnetic iron oxide NPs have also been incorporated into PNIPAM-based hydrogels to enable a magnetic response, which can achieve drug release through remote control with an oscillating magnetic field [71]. Moreover, by adjusting the size of the nanofillers as well as their physical/chemical interactions with the polymeric network, the phase transition temperature of the hydrogel and the responsive speed can also be effectively modulated [73,74,76]. Very recently Czakkel et al gave a comprehensive review about the effect of graphene-derivatives on the responsivity of PNIPAM-based nanocomposites [65].…”

Influence of Graphene Oxide Incorporation on Resorcinol-Formaldehyde Polymer and Carbon Aerogels

“…It is also confirmed that the GO is well distributed in the matrix due to its high oxygen content. The C/O ratio of this GO, determined by XPS, was 1.8 [23].…”

A szénfelület kémiai tulajdonságainak szerepe az anyagtudományban. A Schay-Nagy izotermaegyenlettõl a redukált grafén-oxidig

“…A felületkémiában keresendõ a magyarázata a grafén részecskék pH-érzékeny ülepedési tulajdonságainak 8 , alakváltozásának 9 , pH-val szabályozható fém nanorészecske megkötõ képességének 10 . A szén nanorészecskék felületkémiájuktól és alakjuktól képesek befolyásolni reszponzív lágygél kompozitokban azok hõmérsékletváltozásra vagy IR besugárzásra adott válaszát is 11,12 .…”