Pyrene-based functionalized graphene has been used for reversible addition fragmentation chain transfer (RAFT) polymerization of dimethyl aminoethyl acrylate, acrylic acid, and styrene in order to avoid graphene aggregation [18]. The efficient functionalization through MM-102 diazotization of graphene for ATRP of styrene results in high-performance

polymer-graphene Epacadostat nanocomposites with increased tensile strength, T g and Young’s modulus [19]. Covalently bounded polystyrene polymer chains have been systematically tuned using ATRP on single-layer graphene nanosheets by Fang et al. [20]. High-density grafted polymer-graphene nanocomposites exhibit an appreciable increase in T g compared with low-density grafted samples. In this study, we focused on the

functionalization of GO and check details highs-density grafting of poly(methyl methacrylate) (PMMA) chains onto its surface through an in situ ‘grafting from’ technique using ATRP. Quaternization and esterification after diazotization were carried out to increase the number of anchoring sites for ATRP initiators for increased grafting of polymer chains on the GO surface. ATRP of MMA was carried out using GO with ATRP initiators on the surface, cupric bromide (CuBr, catalyst), and N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA, ligand) at ambient the temperature. The resulting graphene-PMMA nanocomposites showed higher thermal stability and higher glass transition temperatures (T g ) than pristine PMMA polymers. Methods Acid-treated natural expandable graphite (grade 1721) was purchased from Asbury Carbons, Asbury, NJ, USA. Concentrated sulfuric acid (H2SO4), potassium permanganate (KMnO4), sodium nitrate (NaNO3), sodium nitrite (NaNO2), sodium carbonate (Na2CO3), hydrochloric acid (HCl, 35%), hydrogen peroxide (H2O2, 30 wt.%), N,N′-dimethylformamide

(DMF), MMA, 2-chloroethanol, p-aminobenzoic acid, and 2,2′,2″”-trihydroxy-triethylamine (triethanolamine) were purchased from Daejung Reagents & Chemicals, Ulsan, Korea. Cuprous bromide (CuBr), N,N,N′,N″,N″-PMDETA and polystyrene standards for gel permeation chromatography (GPC) were purchased from Sigma-Aldrich, St. Louis, MO, USA and were used as received without further purification. The stabilizing agent was removed from commercial MMA by washing three times with sodium hydroxide (NaOH), followed by vacuum distillation; the middle portion was stored at 0°C to 4°C until use. DMF was stirred with anhydrous calcium hydride (CaH2) and then distilled before use. Preparation of DGO-Br The preparation steps of GO, diazotized GO (DGO-COOH), tetrakis(2-hydroxyethyl) ammonium chloride (THAC), DGO-COO−Na+, and DGO-OH have been reported in our previous paper [21].