Surface modification of graphene oxide with thermoresponsive polymers via atom transfer radical polymerization: Transition from LCST to UCST

Graphene oxide-poly(2-N,N-dimethylamino)ethyl methacrylate (GO-PDMAEMA) nanocomposite was synthesized via atom transfer radical polymerization (ATRP) and PDMAEMA chains were grafted on the surface of GO. After quaternization, quaternized GO-PDMAEMA nanocomposite was achieved. GO-PDMAEMA shows a lower critical solution temperature (LCST)-type thermoresponsivity, and the dispersion-aggregation behavior was controlled by changing the temperature of the solution. The hydrophilicity of GO-PDMAEMA decreased with increasing temperature. Conversely, the dispersion and hydrophilicity of quaternized GO-PDMAEMA increased with increasing temperature due to the upper critical solution temperature (UCST)-type thermoresponsivity. So the LCST–UCST transition can be accomplished by the transition of PDMAEMA to quaternized PDMAEMA on the surface of GO.