In situ repair of graphene defects and enhancement of its reinforcement effect in polyvinyl alcohol hydrogels

Abstract

Defects cause unexpected and unsatisfactory effects in graphene when it is used as a reinforcement in composites. Herein, γ-ray irradiation was introduced as a facile and efficient method to simultaneously repair the defects of reduced graphene oxide (rGO) and enhance the reinforcement effect of graphene in a polyvinyl alcohol (PVA) matrix. Under the action of γ-ray irradiation, the surfaces of rGO were activated and free radicals were produced on PVA chains. At higher irradiation doses, random chain scissions of the PVA main-chain were linked with the reactive groups around the edge of defects on the rGO, leading to the repair of the crystalline graphene, which was evidenced by the decrease of I_D/I_G and stronger 2D bands of the irradiated PVA/rGO hydrogel composites. Thus, the reinforcement effect of graphene is enhanced by γ-ray irradiation. The tensile and compressive strength of the PVA/rGO hydrogel composites achieved their maximum values at irradiation doses of 100 kGy and 150 kGy, respectively, which were 44% and 171% higher than the nonirradiated composites, and 113% and 336% higher than those of pure PVA hydrogel, respectively.