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Interactions of cellulose and model surfaces
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
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: urn:nbn:se:kth:diva-619ISBN: 91-7178-260-5 (print)OAI: oai:DiVA.org:kth-619DiVA: diva2:14636
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
List of papers
1. Forces between silica surfaces with adsorbed cationic surfactants:  Influence of salt and added non-ionic surfactant
Open this publication in new window or tab >>Forces between silica surfaces with adsorbed cationic surfactants:  Influence of salt and added non-ionic surfactant
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.

Keyword
Adhesion, Adsorption, Atomic force microscopy, Ellipsometry, Hydration, Hydrogen bonds, Interfacial energy, pH effects, Silica
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-9074 (URN)10.1021/la047763a (DOI)000227193500034 ()2-s2.0-14844334915 (Scopus ID)
Note
QC 20100915Available from: 2006-02-10 Created: 2006-02-10 Last updated: 2017-12-14Bibliographically approved
2. Friction between cellulose surfaces and the effect of and xyloglucan adsorption
Open this publication in new window or tab >>Friction between cellulose surfaces and the effect of and xyloglucan adsorption
Show others...
2006 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, no 7, 2147-2153 p.Article in journal (Refereed) Published
Abstract [en]

The forces and friction between cellulose spheres have been measured in the absence and presence of xyloglucan using an atomic force microscope. The forces between cellulose are monotonically repulsive with negligible adhesion after contact is achieved. The friction coefficient is observed to be unusually high in comparison with other nanotribological systems. We have confirmed that xyloglucan adsorbs strongly to cellulose, which results in a much stronger adhesion, which is dependent on the time the surfaces are in contact. Xyloglucan also increases the repulsion on approach of the cellulose surfaces, and the friction is markedly reduced. The apparently incompatible observations of decreased friction in combination with increased adhesion fulfills many of the necessary criteria for a papermaking additive.

Keyword
ATOMIC-FORCE MICROSCOPY, COLLOIDAL PROBE MICROSCOPY, PLANT-CELL WALL, ADSORBED POLYELECTROLYTE LAYERS, TORSIONAL SPRING CONSTANT, SILICA SURFACES, ADHESION, FILMS, CONFORMATIONS, PAPERMAKING
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-9075 (URN)10.1021/bm060100i (DOI)000238848800010 ()2-s2.0-33746287565 (Scopus ID)
Note
QC 20100915. Uppdaterad från Submitted till Published (20100915)Available from: 2006-02-10 Created: 2006-02-10 Last updated: 2017-12-14Bibliographically approved
3. Effect of capillary condensation on friction force and adhesion
Open this publication in new window or tab >>Effect of capillary condensation on friction force and adhesion
Show others...
2007 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 2, 517-522 p.Article in journal (Refereed) Published
Abstract [en]

Friction force measurements have been conducted with a colloid probe on mica and silica (both hydrophilic and hydrophobized) after long (24 h) exposure to high-humidity air. Adhesion and friction measurements have also been performed on cellulose substrates. The long exposure to high humidity led to a large hysteresis between loading and unloading in the friction measurements with separation occurring at large negative applied loads. The large hysteresis in the friction - load relationship is attributed to a contact area hysteresis of the capillary condensate which built up during loading and did not evaporate during the unloading regime. The magnitude of the friction force varied dramatically between substrates and was lowest on the mica substrate and highest on the hydrophilic silica substrate, with the hydrophobized silica and cellulose being intermediate. The adhesion due to capillary forces on cellulose was small compared to that on the other substrates, due to the greater roughness of these surfaces.

Keyword
Adhesion, Atmospheric humidity, Condensation, Friction, Hysteresis, Mica, Silica, Surface roughness
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-9041 (URN)10.1021/la060456f (DOI)000243338500031 ()2-s2.0-33846881797 (Scopus ID)
Note
QC 20100909. Uppdaterad från Submitted till Published (20100909)Available from: 2006-01-27 Created: 2006-01-27 Last updated: 2017-12-14Bibliographically approved
4. Friction and forces between cellulose model surfaces: A comparison
Open this publication in new window or tab >>Friction and forces between cellulose model surfaces: A comparison
Show others...
2006 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 303, no 1, 117-123 p.Article in journal (Refereed) Published
Abstract [en]

Four different cellulose model surfaces, and one silica surface, have been studied by means of atomic force microscopy (AFM). The normal interactions 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 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. All studied cellulose surfaces show similar behavior in response to xyloglucan addition.

Keyword
AFM; cellulose; surface forces; colloid probe; xyloglucan; nanotrilology; friction
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-7721 (URN)10.1016/j.jcis.2006.06.070 (DOI)000241079500015 ()2-s2.0-33748919455 (Scopus ID)
Note
QC 20100804Available from: 2007-11-25 Created: 2007-11-25 Last updated: 2017-12-14Bibliographically approved
5. A novel technique for the in situ calibration and measurement of friction with the atomic force microscope
Open this publication in new window or tab >>A novel technique for the in situ calibration and measurement of friction with the atomic force microscope
2005 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 76, no 8, 083710- p.Article in journal (Refereed) Published
Abstract [en]

 Presented here is a novel technique for the in situ calibration and measurement of friction with the atomic force microscope that can be applied simultaneously with the normal force measurement. The method exploits the fact that the cantilever sits at an angle of about 10 degrees to the horizontal, which causes the tip (or probe) to slide horizontally over the substrate as a normal force run is performed. This sliding gives rise to an axial friction force (in the axial direction of the cantilever), which is measured through the difference in the constant compliance slopes of the inward and outward traces. Traditionally, friction is measured through lateral scanning of the substrate, which is time consuming, and requires an ex situ calibration of both the torsional spring constant and the lateral sensitivity of the photodiode detector. The present method requires no calibration other than the normal spring constant and the vertical sensitivity of the detector, which is routinely done in the force analysis. The present protocol can also be applied to preexisting force curves, and, in addition, it provides the means to correct force data for cantilevers with large probes.

Keyword
TORSIONAL SPRING CONSTANT; ADHESION MEASUREMENTS; CANTILEVERS; SURFACTANT; MONOLAYERS; TILT
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-9078 (URN)10.1063/1.2006407 (DOI)000231276600035 ()2-s2.0-26444462128 (Scopus ID)
Note
QC 20100824Available from: 2006-02-10 Created: 2006-02-10 Last updated: 2017-12-14Bibliographically approved

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