A series of fluorinated diblock copolymers consisting of poly(styrene-r-acrylonitrile) (PSAN) and poly (1,1,2,2-tetrahydroperfluorooctyl methacrylate) (PFOMA) were prepared by atom transfer radical polymerization (ATRP). The copolymers with well-controlled molecular weight and narrow molecular weight distribution (PDI < 1.2) were characterized by H-1 NMR, GPC, and FTIR. With the amphiphilic diblock copolymers as stabilizers, acrylonitrile-vinyl acetate random copolymers were synthesized by dispersion polymerization in supercritical carbon dioxide (ScCO2)Compared with precipitation polymerization, the products prepared via dispersion polymerization possess of higher yield and higher molecular weight. In addition, via dispersion polymerization, the particle morphology of the product is spherical. And the dispersity index of the particle size distribution is very narrow. At the same reaction condition, the particle morphology of the product prepared by precipitation polymerization is irregular. (c) 2006 Wiley Periodicals, Inc.