Adsorption Isotherms of Aqueous C12E6 and Cetyltrimethylammonium Bromide Surfactants on Solid Surfaces in the Presence of Low Molecular Weight Coadsorbents

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• 作者：Liu Shi ; Manuel Ghezzi ; Gabriella Caminati ; Pierandrea Lo Nostro ; Brian P. Grady ; Alberto Striolo
• 刊名：Langmuir
• 出版年：2009
• 出版时间：May 19, 2009
• 年：2009
• 卷：25
• 期：10
• 页码：5536-5544
• 全文大小：830K
• 年卷期：v.25,no.10(May 19, 2009)
• ISSN：1520-5827

文摘

In this work, we evaluate the effects of the low molecular weight compounds toluene, phenol, and 1-hexanol on the adsorption of two surfactants on one solid surface. The surfactants are cetyltrimethylammonium bromide (CTAB, cationic) and hexaethylene glycol monododecyl ether (C₁₂E₆, nonionic). The surface is gold, although X-ray photoelectron spectroscopic analysis reveals the presence of a large number of oxygenated sites that render the surface hydrophilic (contact angle 10°). Adsorption isotherms are measured using a quartz crystal microbalance with dissipation monitoring (QCM-D). Although our measurements do not allow the determination of the morphology of the aggregates directly, we rationalize our results by referring to AFM images from the literature. On the basis of primarily the dissipative signal and on AFM studies done by others, our results are consistent with CTAB forming a patchy cylindrical structure and C₁₂E₆ likely yielding a monolayer structure. The presence of cosolutes almost doubles the mass of surface aggregates and increases the rigidness of the aggregates for CTAB, consistent with a morphological change from cylinders to flat bilayers. Part of the increase in adsorbed mass is likely due to increased surface area covered by admicelles. For C₁₂E₆, cosolutes cause small changes in the mass adsorption and essentially no change in the flexibility of surface aggregates.