Strong and conductive double-network graphene/PVA gel

Abstract

Two kinds of graphene gel are prepared from graphene oxide (GO) by a hydrothermal method. The average sheet size of graphene gel with smaller GO (sG gel) is 0.75 μm², while that of graphene gel with larger GO (lG gel) is 12.5 μm². Both the sG gel and lG gel have a three dimensional graphene framework. The sG gel has better mechanical and electrical properties than the lG gel because of the smaller pore size and higher graphene density. Furthermore, graphene/polyvinyl alcohol double-network hydrogels (G/PVA gel) were fabricated by introduction of PVA chains into graphene hydrogels followed by freezing and thawing for the first time. The compressive fracture strength could reach as high as 213 kPa for sG/PVA gel and 104 kPa for lG/PVA gel, which were 245% and 243% higher than the corresponding sG gel and lG gel, respectively. This could be due to the good interaction, entanglement and support of each other between the PVA network and graphene network. G/PVA gel was conductive because of the well-preserved intact graphene network. Cyclic compressing and recovery tests demonstrated that the structure and mechanical properties of the gels were stable. And the conductivity was strain-sensitive, which increased with strain increasing when compressing and decreased with strain recovery. The novel properties make the G/PVA gel attractive in a wide variety of applications, such as cartilage, sensors and high performance nanocomposites.