The central theme of this thesis is the wetting behaviour of phase-separated mixtures of non-adsorbing polymer and spherical solid colloids dispersed in a liquid. The phase behavior of this kind of colloid-polymer mixtures is regulated by depletion interactions. These depletion interactions exist between particles, but also between a particle and a flat substrate. Therefore, wetting behaviour is also regulated by these depletion interactions. Because both phase behaviour and wetting behaviour of colloid-polymer mixtures are regulated by depletion interactions it is important to quantify the depletion interaction. Therefore we also investigated this depletion interaction itself. In this first chapter of this thesis, depletion interactions and phase behaviour of colloid-polymer mixtures will be reviewed. Furthermore, some concepts concerning wetting will be introduced. In the second chapter we present measurements of the depletion interaction between surfaces in the presence of a non-adsorbing polymer solution. The instrument used for these measurements is the colloidal probe atomic force microscope. In the third chapter, investigations on the wetting behaviour of phase separated colliod polymer mixtures near a hard wall are reported. In chapter four the latter theme is discussed in more detail and extended to wetting phenomena near a 'soft' (polymer-covered) wall.
Wijting, Willem Karel