Preparation of Nonspherical Elastic Silicone Particles by Liquid–Liquid Phase Separation

Abstract Nonspherical polymer particles offer unique and controllable properties owing to their anisotropy, but have primarily been based on hard and brittle vinyl polymers with low durability. Silicone particles have high elasticity, but few studies have examined the preparation of nonspherical silicone particles. In this study, nonspherical silicone particles were prepared by utilizing liquid–liquid phase separation within monodisperse composite droplets. Monodisperse composite droplets were prepared by the sol–gel process from 3-methacryloxypropylmethyldimethoxysilane and a toluene/heptane mixed solvent. This mixed solvent was selected as the second component owing to its miscibility with silicone oil at high temperatures but immiscibility upon cooling, which enabled phase separation within the droplets. Radical polymerization and removal of the second component resulted in nonspherical vase-shaped silicone particles whose morphology could be controlled by changing the ratio of silicone oil to the second component. Moreover, the exposure of the second component to the medium could be controlled by adjusting the amount of sodium dodecyl sulfate. Siloxane bonds were extended by anionic ring-opening polymerization to improve elasticity. The particle orientation in the dry state could be controlled by utilizing the density difference between silicone and the toluene/heptane mixed solvent.