全氟辛酸钠和溴化烷基三甲铵混合水溶液的界面化学性质

测定了一系列不同比例的C_7F_(15)COONa与阳离子表面活性剂(C_3H_(17)N(CH_3)Br、C_(10)H_(21)N(CH_3)_3Br和C_(12)H_(25)N(CH_3)_3Br)混合水溶液(加NaBr, 恒离子强度μ=0.1 mol kg~(-1))的表面张力及正庚烷/水溶液界面张力。结果表明: 在表面上, 随阳离子表面活性剂碳氢链长增加, 各体系同一比例的饱和总吸附量增大。界面上, 7CFNa～C_8NBr体系的吸附规律与表面相似; 7CFNa～C_(10)NBr体系饱和总吸附量在1:1时最小; 而7CFNa～C_(12)NBr体系, 其饱和吸附量随7CFNa比例减小而减小。混合物的表(界)面活性均比单一表面活性剂高。随着阳离子表面活性剂碳氢链增加, 混合溶液降低表面张力的能力有所下降, 而降低表面张力的效率有所提高, 自表面吸附层结构与表面张力的关系对比作了说明。

INTERFACE CHEMICAL PROPERTIES OF THE MIXED AQUEOUS SOLUTION OF SODIUM PERFLUOROOCTANOATE AND ALKYLTRIMETHYLAMMONIUM BROMIDE

The interface adsorption and micelle formation of the mixed solution of fluorocarbon and hydrocarbon surfactants (7CFNa and C_8NBr, C_(10)NBr, C_(12)NBr mixtures) have been investigated. The surface tension and interfacial tension of the mixed solution have been determined by the drop-volume method (the ionic strengths of the solution are kept constant in 0.1 mol~(-1)L by adding NaBr).By applying the Gibbs adsorption equation and using nonideal solution theory, the total adsorption amount and the individual adsorption amounts of each surfactant have been obtaioned. It has been shown that (I) at the surface the adsorption rules of various systems are essentially the same. At the heptane/water interface, the adsordtion rule of 7CFNa-C_3NBr system is similar to that at the surface, for 7CFNa-C_(10)NBr mixture the amount of satuated adsorption increases with increase in the molar ratio of any one surfactant from the 1:1 ratio at which the saturated adsorption amount is the least. However, the saturated adsorption amount for 7CFNa-C_(12)NBr system decreases with decrease in the mole ratio of 7CFNa in the mixture the adsorption rule is contrary to that at the surface; (2) The surfactant mixture has a very high interfacial activity. The efficiency of surface tension decreases and the effectiveness of surface tension increases with the increase in hydrocarbon chain length in cationic surfactants.