Spherical, Dimpled, and Crumpled Hybrid Colloids with Tunable Surface Morphology.

Surface morphology is a tool to tune physical properties of colloidal suspensions such as the wettability, viscoelasticity, and depletion attractions. Existing synthesis methods to obtain colloids with a rough surface morphology often result in colloids with nontunable surface properties. Here, we developed a synthetic approach to obtain both spherical and shape-anisotropic hybrid colloids with tunable surface morphology. With our approach, monodisperse linear polystyrene colloids, obtained in large quantities using a dispersion polymerization method, are swollen and cross-linked with styrene and 3-(trimethoxysilyl)propyl methacrylate (TPM) in the presence of the polymerization inhibitor hydroquinone. We show that, by varying only two experimental parameters, the concentration of the inhibitor and of TPM during swelling linear polystyrene colloids, three different types of particles can be synthesized. At low TPM concentrations, spherical colloids are obtained where the surface roughness can be tuned by varying the hydroquinone concentration. At intermediate TPM concentrations, single-dimpled colloids are formed with tunable dimple size. High TPM concentrations yield crumpled colloids of various shapes. Additionally, we demonstrate that all particles can be used as templates for silica coating, resulting in electrostatically stabilized silica-coated hybrid colloids or silica shells with rough, smooth, dimpled, or crumbled surface morphology.