Graphene nanosheets offer intriguing electronic, thermal and mechanical properties and are expected to find a variety of applications in high-performance nanocomposite materials. The great challenge of exfoliating and dispersing pristine graphite or graphene sheets in various solvents or matrices can be achieved by facilely and properly chemical functionalization of the carbon nanosheets. Here we reported an efficient way to functionalize graphene sheets with presynthesized polymer via a combination of atom transfer nitroxide radical coupling chemistry with the grafting-onto strategy, which enable us to functionalize graphene sheets with well-defined polymer synthesized via living radical polymerization. A radical scavenger species, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), was firstly anchored onto COOH groups on graphene oxide (GO) to afford TEMPO-functionalized graphene sheets (GS-TEMPO), meanwhile, the GO sheets were thermally reduced. Next, GS-TEMPO reacted with Br-terminated well-defined poly(N-isopropylacrylamide) (PNIPAM) homopolymer, which was presynthesized by SET-LRP, in the presence of CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine to form PNIPAM-graphene sheets (GS-PNIPAM) nanocomposite in which the polymers were covalently linked onto the graphene via the alkoxyamine conjunction points. The PNIPAM-modified graphene sheets are easily dispersible in organic solvents and water, and a temperature-induced phase transition was founded in the water suspension of GS-PNIPAM. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A series of fluorine-containing amphiphilic diblock copolymers comprising hydrophobic poly(p-(2-(p-tolyloxy)perfluorocyclobutoxy)phenyl methacrylate) (PTPFCBPMA) and hydrophilic poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) segments were synthesized via successive reversible addition fragmentation chain transfer (RAFT) polymerizations. RAFT homopolymerization of p-(2-(p-tolyloxy)perfluorocyclobutoxy)phenyl methacrylate was first initiated by 2,2′-azobisisobutyronitrile using cumyl dithiobenzoate as chain transfer agent, and the results show that the procedure was conducted in a controlled way as confirmed by the fact that the number-average molecular weights increased linearly with the conversions of the monomer while the polydispersity indices kept below 1.30. Dithiobenzoate-capped PTPFCHPMA homopolymer was then used as macro-RAFT agent to mediate RAFT polymerization of 2-(diethylamino)ethyl methacrylate, which afforded PTPFCBPMA-b-PDEAEMA amphiphilic diblock copolymers with different block lengths and narrow molecular weight distributions (M_w/M_n ≤ 1.28). The critical micelle concentrations of the obtained amphiphilic diblock copolymers were determined by fluorescence spectroscopy technique using N-phenyl-1-naphthylamine as probe. The morphology and size of the formed micelles were investigated by transmission electron microscopy and dynamic light scattering, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A mild and efficient strategy is presented for growing thermo-sensitive polymers directly from the surface of exfoliated graphene oxide (GO). This method involves the covalent attachment of Br-containing initiating groups onto the surface of GO sheets followed by in situ growing poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) via single-electron-transfer living radical polymerization (SET-LRP). Considering the lack of reactive functional groups on the surface of GO, exfoliated GO sheets were subjected to an epoxide ring opening reaction with tris(hydroxymethyl) aminomethane (TRIS) at room temperature. The initiating groups were grafted onto TRIS-GO sheets by treating hydroxyls with 2-bromo-2-methylpropionyl bromide at room temperature. PPEGEEMA chains were synthesized by in situ SET-LRP using CuBr/Me₆TREN as catalytic system at 40 °C in H₂O/THF. The resulting materials were characterized using a range of testing techniques and it was proved that polymer chains were successfully introduced to the surface of GO sheets. After grafting with PPEGEEMA, the modified GO sheets still maintained the separated single layers and the dispersibility was significantly improved. This TRIS-GO-PPEGEEMA hybrid material shows reversible self-assembly and deassembly in water by switching temperature at about 34 °C. Such smart graphene-based materials promise important potential applications in thermally responsive nanodevices and microfluidic switches. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011