期刊
JOURNAL OF COLLOID AND INTERFACE SCIENCE
卷 251, 期 1, 页码 18-25出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1006/jcis.2002.8358
关键词
adsorption kinetics; mixed barrier-diffusion control; adsorption; from micellar surfactant solutions; demicellization; rate constant; dynamic surface tension; theoretical analysis; kinetics of adsorption; short- and long-time asymptotics; micelles; role in surface tension relaxation; nonionic surfactants; kinetics of adsorption
Relaxation processes of surfactant adsorption and surface tension, which are characterized by two specific relaxation times, are theoretically investigated. We are dealing with fluid interfaces and small initial deviations from equilibrium. For surfactant concentrations below the critical micellization concentration (CMC), we consider adsorption under mixed barrier-diffusion control. General analytical expressions are derived, which are convenient for both numerical computations and asymptotic analysis. Series expansions for the short- and long-time limit are derived. The results imply that the short-time asymptotics is controlled by the adsorption barrier, whereas the long-time asymptotics is always dominated by diffusion. Furthermore, for surfactant concentrations above the CMC, adsorption under mixed micellization-diffusion control is considered. Again, a general analytical expression is derived for the relaxation of surfactant adsorption and surface tension, whose long- and short-time asymptotics are deduced. The derived equations show that at the short times the relaxation is completely controlled by the diffusion, whereas the long-time asymptotics is affected by both demicellization and diffusion. The micellar effect is manifested as an exponential (rather than square-root) decay of the perturbation. The derived expressions are applied to process available experimental data for the nonionic surfactant Triton X-100 and to determine the respective demicellization rate constant. (C) 2002 Elsevier science (USA).
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