☆ 4.7 Article

Hydrophilicity and flexibility of the spacer as critical parameters on the aggregation behavior of long alkyl chain cationic gemini surfactants in aqueous solution

JOURNAL OF MOLECULAR LIQUIDS (2017)

期刊

JOURNAL OF MOLECULAR LIQUIDS

卷 230, 期 -, 页码 453-460

出版社

ELSEVIER SCIENCE BV

DOI: 10.1016/j.molliq.2017.01.053

关键词

Gemini surfactant; Trimeric surfactant; Spacer; Aggregation behavior; Critical micelle concentration; Aggregation number

类别

Chemistry, Physical Physics, Atomic, Molecular & Chemical

资金

Spanish Ministerio de Economia y Competitividad [CTQ2013-41514-P]
National Center for Research and Development [TANG01/266340/NCBR/2015]
European Commission

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摘要

Series of quaternary ammonium-based gemini surfactants with long alkyl chains (C12 and C18) containing different spacers and substituents attached to the polar head group have been synthesized and their aggregation properties in aqueous solution examined. The effect of the hydrophobic chain, the nature and structure of the spacer group and the polarity of the head group on the aggregation behavior of such dimeric surfactants has been investigated. The critical micelle concentration (cmc) values of gemini surfactants in aqueous solution were determined by conductivity, steady state fluorescence and potentiometric measurements. The size of aggregates formed by investigated amphiphiles above the cmc in aqueous solution was examined by dynamic light scattering. Gemini surfactants show cmc values significantly lower than those of comparable single chain surfactants. The tendency of trimeric surfactants with a rigid spacer to form aggregates is higher than that of the corresponding dimeric surfactants. As occurs for monomeric ionic surfactants, the cmc of gemini surfactants decreases with the elongation of the hydrophobic chain. However, the effect of lengthening the alkyl chain on the cmc depends on the structure of the spacer. C12 gemini surfactants with a rigid hydrophobic spacer exhibit cmc higher than those containing a flexible hydrophobic spacer. For gemini surfactants with C18 alkyl chains this effect is even more pronounced and leads to differences in cmc values greater than one order of magnitude. The structure of the spacer, flexible or rigid chain, has been found to be a critical parameter on the self-assembly of long chain gemini surfactants. Spherical micelles are spontaneously formed above the cmc for C12 gemini surfactants, whereas trimeric and C18 gemini surfactants seems to form vesicle-like aggregates when self-aggregation occurs. (C) 2017 Elsevier B.V. All rights reserved.

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Self-aggregation of cationic gemini surfactants with amide groups in the spacer and variable alkyl chain length

Martin Pisarcik, Martin Bajcura, Milos Lukac, Ferdinand Devinsky, Andrea Bilkova, Frantisek Bilka, Branislav Horvath

Summary: Novel cationic gemini surfactants with two amide groups and variable alkyl chain lengths were synthesized and characterized. The critical micelle concentration of the surfactants was determined and correlated with interfacial area, micelle ionisation degree, and thermodynamics properties. The formation of small spherical micelles was confirmed by particle size analysis, and the zeta potential of the surfactants increased with longer alkyl chain lengths. The antimicrobial activity of the surfactants showed a dependence on alkyl tail length, with the short-chain surfactant exhibiting the highest efficiency.

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