One-Pot Controlled Synthesis of Homopolymers and Diblock Copolymers Grafted Graphene Oxide Using Couplable RAFT Agents

An original strategy is presented to synthesize homopolymers and diblock copolymers grafted graphene oxide by simultaneous coupling reaction and RAFT process. Z-functionalized S-methoxycarbonylphenylmethyl S'-3-(trimethoxysilyl)propyltrithiocarbonate (MPTT) and R-functionalized S-4-(trimethoxysilyl)benzyl S'-propyltrithiocarbonate (TBPT) were used as couplable RAFT agents to prepare the target nanocomposites. Under similar conditions, MPTT-mediated grafting reaction was liable to afford grafted chains with shorter chain length, narrower molecular weight distribution and lower grafting density than TBPT-based reaction owing to increased shielding effect and different grafting process. The grafted polymers had nearly controlled molecular weight and polydispersity ranging between 1.11 and 1.38, and the apparent molar grafting ratio was estimated to be 73.6-220 mu mol/g as the molecular weights of grafted polymers were in the range of 3980-12500 g/mol. The improved solubility and dispersibility of GO-polymer composites in various solvents comprising hexane and water confirmed their amphiphilicity. The grafting process offers an opportunity to alter GO morphologies, and surface morphologies involving nanosheets, nanoparticles, and nanorods were observed as the composites were dispersed in different solvents with the aid of sonication treatment. This tandem approach is promising for surface modification of solid substrates with hydroxyl surface due to its mild conditions, straightforward synthesis and good controllability.