Abstract
Aqueous mixtures of cationic hexadecyltrimethylammonium chloride (CTAC) and nonionic pentaethyleneglycol monododecyl ether (C12E5) are investigated. Adsorption layer properties are systematically studied within a wide concentration range for a 1:1 molar ratio of the surfactants. Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry. The interfacial data are juxtaposed to drainage kinetics and stability results for microscopic foam films, investigated by microinterferometric thin liquid film instrumentation. The obtained results give experimental evidence of synergistic interactions in the studied solutions, as compared to the corresponding single surfactant systems. Specific runs of dynamic and equilibrium surface tension curves are registered against the total surfactant quantity; the surface dilatational elasticities for the mixtures are systematically higher. A clear correlation is established between adsorption layer performance and foam film characteristics. The maxima of the film lifetimes are well outlined, and the respective values are shifted towards lower overall concentrations. The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability. The well-expressed synergy observed in adsorption layer and foam film properties suggests the substantial benefits of using mixed surfactant systems in the design and fine-tuning of foam systems for innovative applications.
Highlights
The onset of synergistic stabilization phenomena in aqueous systems containing low molecular mass (LMM) surfactant mixtures is a familiar phenomenon [1,2,3,4]
Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry
The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability
Summary
The onset of synergistic stabilization phenomena in aqueous systems containing low molecular mass (LMM) surfactant mixtures is a familiar phenomenon [1,2,3,4] This synergy is closely related to the specific coupling of structure and properties’ performance as compared to the single surfactant cases. One important aspect that is seldom studied in detail is the impact of the of adsorption layer characteristics at the fluid interfaces on the drainage kinetics and stability of thin liquid films. The latter are essential structural components of foam systems, stabilized by LMM surfactants [5,6,7]. These observations become possible because of the considerable advancements in profile analysis tensiometry (PAT) using oscillating bubbles/droplets [12,13], and the development of microscopic thin liquid instrumentation (TLF) [6,14,15]
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