Colloidal suspensions encompass an enormous class of systems consisting of a continuous and disperse phase which can exists in thermodynamic equilibrium. Their rheological behavior is complex, and in some cases, still poorly understood due to phenomena such as thixotropy, aging, yielding, hysteresis and shear localization. To elucidate the underlying mechanisms related to these complex rheological phenomena model systems are studied. A sticky sphere is an example of a model colloidal particle composed of a polymer brush graphed onto a spherical core.

In this research we explore the mechanisms and structure of gel formation using a model system composed of nano-sized silicon dioxide spheres with 1-octadecanol grafted to the surface and suspended in various aliphatic hydrocarbons. This combination results in a colloidal suspension that crosses the fluid-gel state transition near room temperature and is completely reversible. We exploit scattering techniques (light, and neutrons) to probe the structure of the material at the mesoscopic scale in combination with rheological measurements to study the relationship between stress and deformation of the bulk fluid. Ideally, the information acquired from experimentally studying this model system will lead to a fundamental understanding of gelation and the development of predictive tools that can be applied to more complex systems.