Amphiphilic fluorinated block copolymer synthesized by RAFT polymerization for graphene dispersions

Abstract

Despite the superior properties of graphene, the strong π-π interactions among pristinegraphenes yielding massive aggregation impede industrial applications. For non-covalentfunctionalization of highly-ordered pyrolytic graphite (HOPG), poly(2,2,2-trifluoroethylmethacrylate)-block-poly(4-vinyl pyridine) (PTFEMA-b-PVP) block copolymers were prepared byreversible addition-fragmentation chain transfer (RAFT) polymerization and used as polymericdispersants in liquid phase exfoliation assisted by ultrasonication. The HOPG grapheneconcentrations were found to be 0.260-0.385 mg/mL in methanolic graphene dispersions stabilizedwith 10 wt % (relative to HOPG) PTFEMA-b-PVP block copolymers after one week. Raman andatomic force microscopy (AFM) analyses revealed that HOPG could not be completely exfoliatedduring the sonication. However, on-line turbidity results confirmed that the dispersion stability ofHOPG in the presence of the block copolymer lasted for one week and that longer PTFEMA and PVPblocks led to better graphene dispersibility. Force-distance (F-d) analyses of AFM showed that PVPblock is a good graphene-philic block while PTFEMA is methanol-philic.