Are Hydrotropes Distinct from Surfactants?

详细信息    查看全文

• 作者：Marios Hopkins Hatzopoulos ; Julian Eastoe ; Peter J. Dowding ; Sarah E. Rogers ; Richard Heenan ; Robert Dyer
• 刊名：Langmuir
• 出版年：2011
• 出版时间：October 18, 2011
• 年：2011
• 卷：27
• 期：20
• 页码：12346-12353
• 全文大小：892K
• 年卷期：v.27,no.20(October 18, 2011)
• ISSN：1520-5827

文摘

The physicochemical properties of a homologous series of sodium p-n-alkylbenzoates have been investigated. The objective was to determine whether there is a clear transition point from hydrotropic to surfactant-like behavior with increasing alkyl chain length n, so as to shed clear light on the aggregation mechanism of so-called 鈥渉ydrotropes鈥? Electrical conductivity measurements were used for a first estimation of the critical aggregation concentrations (cac). As for classical surfactants, log(cac) depends on alkyl chain length n, but two branches of behavior were observed: one having a gradient typical of long chain fatty acid salts and the other with a more shallow dependence. Surface tension (纬) measurements of high purity aqueous solutions were used to generate limiting headgroup areas A_cac, which were in the range (40鈥?0 脜²) being consistent with monolayer formation. Small-angle neutron scattering conclusively shows that the lower chain length homologues (classed as hydrotropes) exhibit sharp transitions in aggregation as a function of bulk concentration, typical of regular surfactants. As such, there is little to suggest from this study that hydrotropes differ in association behavior from regular surfactants.