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Forces between silica surfaces with adsorbed cationic surfactants:  Influence of salt and added non-ionic surfactant
KTH, School of Chemical Science and Engineering (CHE), Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.ORCID iD: 0000-0002-8935-8070
2005 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 5, 1875-1883 p.Article in journal (Refereed) Published
Abstract [en]

Forces have been measured between silica surfaces with adsorbed surfactants by means of a bimorph surface force apparatus. The surfactants used are the cationic surfactant tetradecyltrimethylammonium bromide (TTAB) and the nonionic surfactant hexakis(ethylene glycol) mono-n-tetradecyl ether (C14E6) as well as mixtures of these two surfactants. The measurements were made at elevated pH, and the effect of salt was studied. At high pH the glass surface is highly charged, which increases the adsorption of TTAB. Despite the low adsorption generally seen for nonionic surfactants on silica at high pH, addition Of C14E6 has a considerable effect on the surface forces between two glass surfaces in a TTAB solution. The barrier force is hardly affected, but the adhesion is reduced remarkably. Also, addition of salt decreases the adhesion, but increases the barrier force. In the presence of salt, addition Of C14E6 also increases the thickness of the adsorbed layer. The force barrier height is also shown to be related to literature values for surface pressure data in these systems.

Place, publisher, year, edition, pages
2005. Vol. 21, no 5, 1875-1883 p.
Keyword [en]
Adhesion, Adsorption, Atomic force microscopy, Ellipsometry, Hydration, Hydrogen bonds, Interfacial energy, pH effects, Silica
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-9074DOI: 10.1021/la047763aISI: 000227193500034Scopus ID: 2-s2.0-14844334915OAI: oai:DiVA.org:kth-9074DiVA: diva2:14631
Note
QC 20100915Available from: 2006-02-10 Created: 2006-02-10 Last updated: 2010-09-15Bibliographically approved
In thesis
1. Interactions of cellulose and model surfaces
Open this publication in new window or tab >>Interactions of cellulose and model surfaces
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The focus of this thesis is fundamental surface force and friction studies of silica and cellulose surfaces, performed mainly with the atomic force microscope (AFM). The normal interactions between model cellulose surfaces have been found to consist of a longer range double layer force with a short range steric interaction, the nature of which is extensively discussed. Both the surface charge and range of the steric force depend on the type of cellulose substrate used, as does the magnitude of the adhesion. Studies of friction on the same surfaces reveal that surface roughness is the determining factor for the friction coefficient, with which it increases monotonically. The absolute value, however, is determined by the surface chemistry.

The above is illustrated by studies of the effect of adsorbed xyloglucan, a prospective paper additive, which is found in the cell wall of all plants. Xyloglucan is like cellulose a poly- saccharide but the effect of its adsorption was to reduce the friction significantly, while following the identical trend with surface roughness. Xyloglucan also increases the adhesion between cellulose surfaces in a time dependent manner, interpreted in terms of a diffusive bridging interaction. These facts combined provide a mechanistic explanation to contemporaneous findings about xyloglucans benefit in paper strength and formation.

In air, the adhesion between e.g. particles or fibres, must be at least partially determined by the formation of capillary condensates. The dependence of capillary condensation on relative humidity is however not yet fully understood so studies have been performed to cast light on this phenomenon. Above about 60 % relative humidity the adhesion and friction increase dramatically due to the formation of large capillary condensates. The extent of the condensates depends both on the time the surfaces equilibrate, but also on the surface roughness. Harvesting of the condensate during shearing is also observed through hysteresis of the friction-load relationship.

Measurements of surface forces and friction in surfactant systems show a clear relation between the adsorbed surfactant layer and the barrier force and adhesion, which in turn determine the friction. All of these interactions are critically dependent on the composition of the surfactant solution. A mixed surfactant system has been studied consisting of a trimethylammonium cationic surfactant and a polyoxyethylene nonionic surfactant. The results are interpreted in terms of current theories of adsorption and synergistic interactions. Finally, a novel technique for the in situ calibration and measurement of friction with the AFM is proposed. Comparison with lateral measurements show that the approach is successful.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 58 p.
Series
Trita-YTK, ISSN 1650-0490 ; 0603
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-619 (URN)91-7178-260-5 (ISBN)
Public defence
2006-02-24, sal F3, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100920Available from: 2006-02-10 Created: 2006-02-10 Last updated: 2011-12-19Bibliographically approved

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