Preparation and characterization of graphene oxide sheets controllably grafted with PMMA brushes via surface-initiated ATRP

Abstract

Recently, graphene oxide (GO) has gained significant attention in many applications, such as touch displays, electronic devices or electrorheological fluids. However, neat GO is hydrophilic, which limits its efficiency in hydrophobic media, e.g. polymer matrices, oil carriers. Therefore, the utilization of GO-coated core-shell structures was proven to be advantageous. In this study, GO sheets were prepared by chemical exfoliation of graphite using modified Hummers method. The specific ATRP initiator, bromoisobutyryl bromide, was covalently immobilized onto as-prepared GO through oxygen-functional hydrophilic groups. Initiator-treated GO sheets were further grafted with poly(methyl methacrylate) (PMMA) via surface-initiated ATRP technique. The monomer conversion, molar mass and polydispersity of PMMA chains were investigated using nuclear magnetic resonance and gel permeation chromatography, respectively. The successful grafting process was confirmed by Fourier transform infrared spectroscopy. Raman spectroscopy and electric conductivity measurements revealed significant chemical reduction of GO during surface-initiated ATRP. Synthesized GO/PMMA structures exhibited considerably enhanced wettability in hydrophobic media, which was proved via contact angle measurements. Therefore, the synthesized GO/PMMA hybrids may found utilization in many aforementioned practical applications providing well-dispersed composite systems.