The role of dimension and shape in colloidal liquids and glasses Público
Vivek, Skanda (2016)
Abstract
In two-dimensions, the laws of physics give rise to intriguing phenomena such as long-range correlations that do not decay at infinity. However, reality can only be quasi-2D at best. This thesis is an effort to bridge the gap between 2D theory and reality, by doing experiments. Here we consider two different model systems - soap films as 2D fluids, and 2D colloidal glass formers. We look at diffusion of tracer particles in soap films and test the validity of 2D theory. We find that for thin films, both 2D surface viscosity and 3D viscosity are important. To a good approximation, soap films are thin films and can be considered 2D for flow. Next, we look at glassy dynamics in 2D and 3D colloidal glass formers. We demonstrate that the differences between 2D and 3D are long-wavelength fluctuations, precisely those that distinguish 2D and 3D phase transitions. Through a novel analysis method that removes the influence of these fluctuations, we show that 2D and 3D glass transitions are otherwise similar. Finally, we look at the effect of shape anisotropy of dimers in 2D glasses, and find that glass dynamics are highly dependent on shape, both in experiments and simulations. These colloidal and simulation results are a prediction of aspect ratio dependent diffusion in real glasses.
Table of Contents
Chapter 1 Introduction. 1
1.1 Dimensionality and physics. 1
1.2 Liquids and dimensionality. 3
1.3 2D viscosity. 5
1.4 Solids and dimensionality. 7
1.5 The glass transition and the colloidal glass transition. 9
1.6 The shape dependent glass transition. 11
Chapter 2 Soap Films as model 2D fluids. 14
2.1 Introduction. 14
2.2 Hydrodynamic theory. 17
2.3 Materials and methods. 22
2.4 Results and Discussion. 32
2.5 Conclusions. 41
Chapter 3 The 2D vs 3D glass transition in colloids. 43
3.1 Introduction. 43
3.2 Materials and Methods. 45
3.3 Results. 49
3.4 Simulations. 60
3.5 Discussion. 62
Chapter 4 Shape dependence approaching the 2D colloidal glass transition. 66
4.1 Introduction. 66
4.2 Imaging and tracking dimers. 72
4.3 Hydrodynamic theory. 72
4.4 Results. 74
4.5 Simulations. 82
4.6 Conclusions. 85
Chapter 5 Summary and outlook. 87
5.1 2D liquids and modeling them through soap films. 87
5.2 2D glass transition. 88
5.3 Shape dependent glass transition. 89
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