Controlling the morphology of polystyrene dumbbell particles

Controlling colloidal particles’ shape is one of the new frontiers in colloidal science. Methods that permit synthesizing polymer particles with a non-spherical shape are increasing and advancing. Of all the non-spherical particles, spheres with protrusions are one of the best investigated, and many recipes have been developed to prepare them. One of the best-developed methods, initially proposed by Park et al. (JACS, 2010), starts with linear polystyrene seed particles, which are swelled and subsequently polymerized with a mixture of styrene and 3-(trimethoxysilyl)propyl methacrylate (MPS). The latter monomer’s hybrid nature creates a hydrophilic and partially crosslinked coating. This prevents the formation of core-shell structure upon further swelling and polymerization with styrene and leads to one or more new lobes. In this work, we investigate many parameters affecting the outcome of this method, including the pH, the duration of the hydrolysis of MPS, its concentration, the presence of crosslinkers in the seed particles, and the use of a different monomer in the last step. The investigation shows the importance of pH control during MPS hydrolysis in the coating step. It also demonstrates that its concentration can effectively be used to control the morphology of the resulting particles, which range from simple one-lobed dumbbells with variable roughness to multilobed particles. Furthermore, a shorter version of the dumbbell synthesis protocol has been obtained. [Display omitted] •Polystyrene dumbbells have been prepared using a seeded polymerization with a hybrid-silane monomer•The effect of the composition of the swelling solution, pH, and hydrolysis conditions of the hybrid silane monomer have been investigated•The shape of the particles can be controlled from single to multiple-lobed particles•A two-step procedure to make dumbbell particles has been proposed