Thermodynamic Properties of Bridging Clusters in Thin Films of Water between Hydrophobic Surfaces Assessed from Surface Force Isotherms
2013 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 15, 4789-4795 p.Article in journal (Refereed) Published
In the course of a long-term effort to cope with surface force data for thin films of water between hydrophobic surfaces, we have applied the bridging-cluster model (Eriksson, J. C.; Henriksson, U. Bridging-cluster model for hydrophobic attraction. Langmuir 2007, 23, 10026-10033) to the recently published surface force isotherms for water films between hexadecylthiolated gold surfaces in the thickness range of 20-100 nm and temperature range of 10-40 degrees C (Wang, J.; Yoon, R.-H.; Eriksson, J. C. Excess thermodynamic properties of thin water films confined between hydrophobized gold surfaces. J. Colloid Interface Sci. 2011, 364, 257-263). We show that these isotherms can be faithfully reproduced on the basis of the bridging-cluster model. The thermodynamic excess properties (Delta G(c), Delta H-c, and T Delta S-c) of linear clusters that are assumed to bridge the core of the films were calculated from the experimental surface force isotherms. A crucial step taken was to infer two-dimensional ideal mixing of the clusters with the surrounding film water. We find that Delta H-c and T Delta S-c are both negative quantities, with the latter being larger than the former, which implies a positive excess Gibbs energy of a cluster, Delta G(c) = Delta H-c - T Delta S-c. Typically, for temperatures between 10 and 40 degrees C, these cluster properties are of the order of some k(B)T units, corresponding to 10(-4)-10(-3)k(B)T per water molecule entailed. Our analysis yields support of the notion that elongated aggregates can arise in thin films of water between hydrophobic surfaces driven by entropy of mixing.
Place, publisher, year, edition, pages
2013. Vol. 29, no 15, 4789-4795 p.
Aqueous-Electrolyte Solutions, Long-Range, Attraction, Nanobubbles
IdentifiersURN: urn:nbn:se:kth:diva-122514DOI: 10.1021/la400446pISI: 000317813300017ScopusID: 2-s2.0-84876258908OAI: oai:DiVA.org:kth-122514DiVA: diva2:622908
QC 201305232013-05-232013-05-232013-05-23Bibliographically approved