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Critical wetting concentrations of trisiloxane surfactants

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journal contribution
posted on 2010-01-22, 12:47 authored by Natalia A. Ivanova, Victor Starov, Ramon Rubio, Hernan Ritacco, Nidal Hilal, Daniel Johnson
Trisiloxane surfactants also known as “superspreaders” are characterized by a critical wetting concentration (CWC) which has been determined by Svitova et al (Langmuir. 1998. 14, 5023- 5031). CWC is a concentration above which a transition from partial wetting to complete wetting occurs at spreading over moderately hydrophobic surfaces, hence, the CWC is associated with the beginning of the superspreading. The latter shows that the knowledge of the CWCs is important for many wetting/spreading applications. We suggest a new method, which allows determining CWCs for a range of trisiloxanes using wetting behaviour of aqueous trisiloxane solutions on highly hydrophobic smooth Teflon AF coated silicon wafers. Using the new method the CWCs for trisiloxane surfactants, Tn with a wide range in the number (n = 4 − 9) of ethylene oxide units have been measured. The critical aggregation concentration (CAC) for trisiloxane surfactants has been measured using the surface tension methods. Additionally, spreading kinetics of all trisiloxane surfactants studied over moderately hydrophobic substrates has been investigated. It has been found that for all trisiloxanes studied the CWCs are several times higher than their corresponding CAC values. The CWCs for T6 and T8 trisiloxanes obtained according to our approach are in agreement with those measured by Svitova et al. (Langmuir. 1998. 14, 5023-5031) for the case of complete wetting. It has been verified that indeed at CWCs estimated according to our approach trisiloxane surfactant solutions demonstrate superspreading behaviour on moderately hydrophobic surfaces with the exception of trisiloxane T4, which still shows only partial wetting. Thus, the CWC does not depend on the degree of hydrophobicity of substrates and could be considered as a distinct property of surfactants that characterize the highest limit of their spreading capability.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Chemical Engineering

Citation

IVANOVA, N.A. ... et al, 2010. Critical wetting concentrations of trisiloxane surfactants. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 354 (1-3), pp.143-148.

Publisher

© Elsevier

Version

  • AM (Accepted Manuscript)

Publication date

2010

Notes

This article was published in the journal, Colloids and Surfaces A: Physicochemical and Engineering Aspects [© Elsevier]. The definitive version is available from: www.elsevier.com/locate/colsurfa

ISSN

0927-7757

Language

  • en

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