脂肪醇聚氧乙烯醚在空气-水界面上铺展单分子膜的脱附性质

Desorption properties for spreading monolayer of a poly (ethylene oxide) alkyl ether at Air-water interface

采用Wilhelmy法测定脂肪醇聚氧乙烯醚在空气 水界面上铺展单分子膜的动态表面压 ,并由此计算动态脱附动力学参数。实验结果表明 ,样品铺展膜的脱附初期扩散系数约 1 0 -3～ 1 0 -4cm2 /sec ,远远大于溶液表面吸附的扩散系数 ,铺展膜的初始表面浓度越大 ,其初期脱附扩散系数也越大。但是从脱附整个过程看 ,铺展膜的初始表面浓度越大 ,其平均脱附速率常数越小 。

The dynamic desorption process of a poly (ethylene oxide) alkyl ether, C_(18)H_(37)O(CH_2CH_2O)_(20)H, in spreading monolayer was measured using dynamic Wilhelmy plate technique at air-water interface. The initial desorption diffusion coefficients o the sample were calculated being about 10^(-3)～10^(-4) cm^2/sec, which are much higher than that of the opposite process in which the sample molecules adsorb from solutions to the surface. However, the bigger the initial surface concentration of the spread monolayer is, the smaller is the average rate constant. It was showed that the desorption process is controlled by a mixed mechanism including both diffusion-controlled and surface energy barrier controlled.