Reversible addition fragmentation chain transfer (RAFT) mediated and conventional miniemulsion copolymerizations of butyl methacrylate (BMA) with fluoromethacrylate (FMA) were carried out at 70 degrees C with potassium persulphate as initiator. The kinetics of the copolymerizations was investigated comparatively. Copolymer compositions at low conversion levels were determined by H-1 NMR and FTIR spectra techniques. In the presence of RAFT agent 2-cyanoprop-2-yl dithiobenzoate, the copolymerization of BMA with FMA in miniemulsion was obviously retarded. The copolymerization exhibited typical features of controlled molecular weights and narrow polydispersities. The reactivity ratios were evaluated by Kellen-Tudos (K-T) method, which yields the apparent reactivity ratios: r(BMA) = 0.73 and r(FMA) = 0.75 in conventional copolymerizations, and r(BMA) = 0.65 and r(FMA) = 0.70 in CPDB-mediated system. The results show that the monomer FMA with a perfluoroalkyl side chain is slightly more reactive than BMA, and the copolymerizations process have a tendency to crosspropagate and to produce a higher FMA content in the copolymers. POLYM. ENG. SCI., 49:1818-1824, 2009. (C) 2009 Society of Plastics Engineers