Disjoining pressure measurements for foam films stabilized by a nonionic sugar-based surfactant

被引:91
作者
Bergeron, V
Waltermo, A
Claesson, PM
机构
[1] ROYAL INST TECHNOL,LAB CHEM SURFACE SCI,DEPT CHEM,S-10044 STOCKHOLM,SWEDEN
[2] INST SURFACE CHEM,S-11486 STOCKHOLM,SWEDEN
关键词
D O I
10.1021/la950594x
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Disjoining pressure isotherms for foam films made from a nonionic surfactant, octyl beta-glucoside, are measured at different surfactant concentrations, ionic strengths, and solution pH values. Below the cmc an electrostatic double-layer repulsion is present and dominates the long-range interaction. The decay length of the forces agrees with the expected Debye length and the measured long-range interactions are consistent with solutions to the nonlinear Poisson-Boltzmann equation using constant charge conditions. The deduced surface charge densities increase with pH and ionic strength but decrease with increasing surfactant concentration. At, or just above, the cmc, surfactant covers the interface and suppresses the charge sufficiently to induce a transition from a common black film to a Newton black film. Ultimately, the film stability is determined by both surface forces and elasticity. Combining both, via an overall film tension, leads to a general expression for the film elasticity.
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页码:1336 / 1342
页数:7
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