Tunable electrorheological performance of silicone oil suspensions based on controllably reduced graphene oxide by surface initiated atom transfer radical polymerization of poly(glycidyl methacrylate)

This article is focused on the controllable reduction of the graphene oxide (GO) particles as a simultaneous process during surface initiated atom transfer radical polymerization (SI-ATRP) providing hybrid particles with tailored conductivity and substantial polymer shell on the particles tunable by SI-ATRP conditions. The main advantage of such approach is that both the compatibility improvement, due to the polymer layer, and conductivity tuning, due to partial GO reduction, were simply achieved in single-step reaction providing electrorheological (ER) system with enhanced performance in comparison to either neat GO or similar non-covalently bonded GO-polymer hybrids. The presence of the poly (glycidyl methacrylate) (PGMA) on the surface of GO was investigated using FTIR spectrometry, transmission electron microscopy and thermogravimetric analysis and their chain length (M-w) and polydispersity index (PDI) were determined by H-1 NMR and GPC, respectively. Two different GO-PGMA particle systems varied in M-w and PDI and also in electrical conductivities were prepared and their electro-responsive capabilities were investigated. The reduction of GO particles was confirmed by Raman shift as well as conductivity measurements. Electrorheological (ER) performance was investigated at various electric field strengths and repeatability of the phenomenon was confirmed by 10 on/off field cycles. Finally, with the help of dielectric measurements of GO-PGMA based ER suspensions, fitted by Havriliak-Negami model, the relaxation processes were properly investigated and the results were correlated with those obtained from electrorheological measurements. (c) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.