Effects of particle deformability on interaction between surfaces in solutions

Interactions between a deformable polymer particle and a solid surface of a mica plate in solutions were investigated using atomic force microscopy (AFM), where the particles have the same surface property but different bulk elasticity. Measurements were done in a solution of cetyltrimethylammonium bromide (CTAB), above its critical micelle concentration (cmc). Under these conditions positively charged layers were formed on both mica and particle surfaces, which induce a high repulsive potential between the approaching surfaces. However, above a critical pressure, the surfaces come in adhesive contact by destroying the adsorbed layers. It was found that the total repulsive force between the surfaces and the force required to adhere the particle to the surface increased significantly if the glass transition temperature of the particle was below the ambient temperature. This indicates that the elastic deformation of the particle as the surfaces are brought together greatly increases the total repulsion within the system. A quantitative interpretation of the data was carried out, using a simple model, which was derived from the theory for elastic body deformation developed by Hughes and White. Results of this study provide significant information on the stability of suspensions of low elastic modulus particles.