全氟庚烷端基聚丙烯酸的制备及其水溶液的表面张力

PREPARATION OF PERFLUOROHEPTYL END- CAPPED POLYACRYLIC ACID AND SURFACE TENSION OF ITS AQUEOUS SOLUTION

Five samples of perfluoroheptyl end capped polyacrylic acid ( F P A A) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produced the free radicalof heptyl at 45 ℃. The yieldsof F P A A were in the range of 10 % to 25 % . The weight average molecular weights were2 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 15m N/m at30 ℃forthe aqueous solution of F P A Awith the weight average molecular weight2 62 ×104in the concentration of about 0 01g/ m L. The molecular areas of F P A A at the air waterinterface under the condition ofcritical micelle concentration were 3 2 to 4 6n m2 ,which areobviously larger than the area per molecule of perfluorooctanoic acid (2 14nm 2) and muchsmaller than that of ordinary polyacrylic acid (83 4nm 2) . It means that the polymermoleculesin the surface adsorbed layer form the brush structure because of the special effectof the perfluoroalkyl groups at the chain ends .