Molecular interactions in mixtures containing surfactants with two hydrophilic and two or three hydrophobic groups.
Item
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Title
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Molecular interactions in mixtures containing surfactants with two hydrophilic and two or three hydrophobic groups.
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Identifier
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AAI9807960
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identifier
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9807960
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Creator
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Liu, Letian.
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Contributor
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Adviser: Milton J. Rosen
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Date
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1997
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical
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Abstract
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A series of novel cationic gemini surfactants, butane 2,3-diol-{dollar}\alpha{dollar}, {dollar}\omega{dollar}-bis(dimethylalkylammonium) bromide (alkyl chain length = 8,10,12,14,16,18), and two series of novel anionic gemini surfactants, 2,5-di(sodium 3-oxypropanesulfonate)-2,5-dialkyl hexane (alkyl chain length = 6, 8, 10, 12) and 2,2{dollar}\sp\prime{dollar}-di(sodium 3-oxypropanesulfonate)-5,5{dollar}\sp\prime{dollar}-dialkyldiphenyl methane (alkyl chain length = 9, 12), were synthesized. Surface properties of these gemini surfactants were investigated by means of surface tension measurements in H{dollar}\sb2{dollar}O and in 0.1 M salt solution at 25{dollar}\sp\circ{dollar}C. The interactions of these geminis with conventional surfactants of different charge type were extensively studied.;It was found that these gemini surfactants had unusually higher surface activities, such as much lower C{dollar}\sb{lcub}20{rcub}{dollar}, cmc values and more closely packed surfactant molecules at the interface, compared to comparable conventional surfactants. However, in contrast to conventional surfactants, the gemini surfactants all showed decreased surface activity at a certain critical chain length. It was proposed that formation of a small, soluble non-surface-active aggregates below the cmc accounts for the above observation. Quantitative calculation of the equilibrium constants for forming these small aggregates below the cmc for longer chain gemini surfactants above the critical chain length then demonstrated that the non-surface active small aggregates are primarily small oligomers of the gemini surfactant.;In a study of the interaction of the gemini surfactants with conventional surfactants of different charge type, it was found that for the geminis having the shorter alkyl chains, strong synergistic interaction occurred in the mixed binary surfactant solutions. However, no synergistic interactions were observed for gemini surfactants having alkyl chain lengths exceeding the critical chain length. The critical chain length for no synergistic interaction depends on the structure of the both gemini and conventional surfactants. The abnormal interaction is attributed to the formation of small, soluble, non-surface active, non-miceller aggregates. Calculations of equilibrium constants for the formation of these aggregates indicated that the two surfactants are present in a 1:1 molar ratio in the aggregate in most of cases.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
