Five samples of perfluoroheptyl end capped polyacrylic acid (FPAA) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produced the free radicalof heptyl at 45℃. The yieldsof FPAA were in the range of 10% to 25% . The weight average molecular weights were 2.62×104 to 7.99×104 and the polydispersity indexes were 1.97 to 5.64

depending on theconcentration of the initiator in the monomer. The surface tension was about 15mN/m at 30℃ for the aqueous solution of FPAA with the weight-average molecular weight 2.62×104 in the concentration of about 0.01g/mL.The molecular areas of FPAA at the air-water interface under the condition of critical micelle concentration were 3.2 to4.6nm2

which are obviously larger than the area per molecule of perfluorooctanoic acid (2.14nm2) and much smaller than that of ordinary polyacrylic acid (83.4nm2).It means that the polymer molecules in the surface adsorbed layer form the brush structure because of the special effect of the perfluoroalkyl groups at the chain ends.