Effects of Structure Variation on Solution Properties of Hydrotropes: Phenyl versus Cyclohexyl Chain Tips

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• 作者：Marios Hopkins Hatzopoulos ; Julian Eastoe ; Peter J. Dowding ; Isabelle Grillo ; Bruno Dem茅 ; Sarah E. Rogers ; Richard Heenan ; Robert Dyer
• 刊名：Langmuir
• 出版年：2012
• 出版时间：June 26, 2012
• 年：2012
• 卷：28
• 期：25
• 页码：9332-9340
• 全文大小：397K
• 年卷期：v.28,no.25(June 26, 2012)
• ISSN：1520-5827

文摘

The physicochemical behavior of the phenyl-n-alkanoate (PhenCx) and cyclohexyl-n-alkanoate (CyclohexCx) series has been investigated, supporting previous work on the understanding of hydrotropes (Hopkins Hatzopoulos, M.; Eastoe, J.; Dowding, P.J.; Rogers, S. E.; Heenan, R.; Dyer, R. Langmuir2011, 27, 12346鈥?2353). Electrical conductivity, surface tension, ¹H NMR, and small-angle neutron scattering (SANS) were used to study adsorption and aggregation in terms of critical aggregation concentration (cac). The PhenCx series exhibited very similar d log(cac)/dn to n-alkylbenzoates (CnBenz), exhibiting two branches of behavior, with a common inflection point at four linear carbons, whereas the CyclohexCx series showed no break point. Electrical conductivity and ¹H NMR concentration scans indicate a difference in physicochemical behavior between higher and lower homologues in both the PhenCx and CyclohexCx series. Surface tension measurements with compounds belonging to either group gave typical Gibbs adsorption profiles, having d log(cac)/dn curves consistent with limiting headgroup areas in the region of (35鈥?5 脜²) indicating monolayer formation. SANS profiles showed no evidence for aggregates below the electrical conductivity determined cac values, inferring an 鈥渙n鈥搊ff鈥?mode of aggregation. Analyses of SANS profiles was consistent with charged ellipsoidal aggregates, persisting from lower through to higher homologues in both the PhenCx and CyclohexCx series.