The Influence of Boundary Roughness on Dense Colloidal Suspensions Open Access
Real, Daniel Jordan (2011)
Published
Abstract
Abstract
The Influence of Boundary Roughness on Dense Colloidal
Suspensions
By Daniel J. Real
We study the relationship between boundary conditions and particle motion in confined, concentrated colloidal suspensions. The study of glassy polymers in confinement has shown that changes in mobility are strongly dependent upon the polymer-surface interaction. We model this interaction by observing the effects of textured surfaces on colloidal particle mobility in confined dense suspensions (near the glass transition). We use confocal microscopy to directly image and track the colloidal particles in thin, wedge-shaped sample chambers made from textured glass. We texture the glass in a controlled, reproducible manner by spincoating and sintering colloidal suspensions onto glass slides. We found that our results were compromised by the presence of unintentional texture on the walls of our smooth slides. Both the mean squared displacement, and the particle distribution within the confining volume were found to be similar in both the textured and smooth walled chambers. Despite a measured volume fraction of φ = 0.42 we observed behavior indicative of a much lower φ in both samples. We did not observe layering within either sample, but we believe this is due to the effectively low φ rather than the textured boundary conditions. Although our results are inconclusive, we have developed a method to create controlled, reproducible textures. In the future, we hope to use these textures to study the dynamics of the glass transition and its dependence on interfacial dynamics versus finite size effects.
Table of Contents
Table of Contents
1 Introduction...1
2 Experimental Methods...5
2.1 Texture Creation...7
3 Results...8
4 Conclusion...12
5 Acknowledgements...13
References...13
List of Figures
1 The difference in Tg from
Tgbulk in
poly(2-vinylpyridine)(P2VP), poly(methyl-methacrylate)
(PMMA), and polystyrene (PS) as a function of film
thickness supported on silica.
Reproduced from Ref. [18]...2
2 Diagram of sample chamber...4
3 Examples of texture created using spincoating...6
4 Texture observed at the boundaries of the "smooth"
chamber...9
5 Value of (Δr2) at Δ t = 100 s, as a function
of thickness H.
Reproduced from Ref [15]...11
6 Mean square displacement for our samples over a range of
thicknesses...16
7 MSD at Δt = 21 s, as a function of thickness H, for samples
with measured φ = 0.42...17
8 Number density n as a function of the distance z between the
walls. Figure 8(a) reproduced from Ref. [7]...18
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