Hydration State of Non-ionic Surfactant Monolayers at the Liquid/Vapor Interface: Structure Determination by Vibrational Sum Frequency Spectroscopy
2005 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, no 48, 16848-16859 p.Article in journal (Refereed) Published
The OH stretching region of water molecules in the vicinity of nonionic surfactant monolayers has been investigated using vibrational sum frequency spectroscopy (VSFS) under the polarization combinations ssp, ppp, and sps. The surface sensitivity of the VSFS technique has allowed targeting the few water molecules present at the surface with a net orientation and, in particular, the hydration shell around alcohol, sugar, and poly(ethylene oxide) headgroups. Dramatic differences in the hydration shell of the uncharged headgroups were observed, both in comparison to each another and in comparison to the pure water surface. The water molecules around the rigid glucoside and maltoside sugar rings were found to form strong hydrogen bonds, similar to those observed in tetrahedrally coordinated water in ice. In the case of the poly(ethylene oxide) surfactant monolayer a significant ordering of both strongly and weakly hydrogen bonded water was observed. Moreover, a band common to all the surfactants studied, clearly detected at relatively high frequencies in the polarization combinations ppp and sps, was assigned to water species located in proximity to the surfactant hydrocarbon tail phase, with both hydrogen atoms free from hydrogen bonds. An orientational analysis provided additional information on the water species responsible for this band.
Place, publisher, year, edition, pages
2005. Vol. 127, no 48, 16848-16859 p.
Alcohols, Hydration, Hydrogen bonds, Interfaces (materials), Surface active agents
IdentifiersURN: urn:nbn:se:kth:diva-7204DOI: 10.1021/ja053289zISI: 000233759200035ScopusID: 2-s2.0-28844477069OAI: oai:DiVA.org:kth-7204DiVA: diva2:12142
QC 20100916. Uppdaterad från Accepted till Published (20100916)2005-09-292005-09-292010-09-16Bibliographically approved