A study on amphiphilic fluorinated block copolymer in graphite exfoliation using supercritical CO₂ for stable graphene dispersion

In this study, poly(2,2,2-trifluoroethyl methacrylate)-block-poly(4-vinylpyridine) (PTFEMA-b-PVP) was synthesized by stepwise reversible addition-fragmentation chain transfer (RAFT) polymerization for the preparation of graphene by the exfoliation of graphite nanoplatelets (GPs) in supercritical CO₂ (SCCO₂). Two different block copolymers (low and high molecular weights) were prepared with the same block ratio and used at different concentrations in the SCCO₂ process. The amount of PTFEMA-b-PVP adsorbed on the GPs and the electrical conductivity of the SCCO₂-treated GP samples were evaluated using thermogravimetric analysis (TGA) and four-point probe method, respectively. All GP samples treated with SCCO₂ were then dispersed in methanol and the dispersion stability was investigated using online turbidity measurements. The concentration and morphology of few-layer graphene stabilized with PTFEMA-b-PVP in the supernatant solution were investigated by gravimetry, scanning electron microscopy, and Raman spectroscopy. Destabilization study of the graphene dispersions revealed that the longer block copolymer exhibited better affinity for graphene, resulting in a higher yield of stable graphene with minimal defects.