Colloidal dumbbells with compositional asymmetries can possess distinct physical properties between two lobes such as the refractive index, electrical polarizability, or photoactivity. They have great potentials in self assembly, autonomous micro-robots, targeted drug delivery, and colloidal emulsifiers. However, it is challenging to synthesize them with well-controlled size, morphology, and compositions. Previous efforts mainly focused on making particles that are made of two different types of polymers. Although they possess some degree of compositional asymmetry, the particles overall are still polymeric. In this talk, we describe a versatile approach to synthesize organic-inorganic hybrid dimers whose chemical compositions (hence the bulk physical properties) are different. We swell the polystyrene seeds with a liquid silicon alkoxide precursor - tetraethyl orthosilicate (TEOS). Because of their immiscibility, a second lobe primarily composed of TEOS can be grown on the seeds. Although it is a liquid, TEOS can undergo sol-gel type hydrolysis and condensation to form solid silica in the presence of a weak base catalyst such as dodecylamine. Analyses based on the scanning electron microscopy, the fluorescent microscopy, and the energy-dispersive X-ray spectroscopy (EDX) confirm both monodisperse morphology and distinctive compositional asymmetry on our particles. Intriguingly, the particle morphology can be conveniently tuned by the adjusting the concentration of base, the amount of TEOS, and the crosslinking density of the seeds. Because the surfaces of polystyrene and silica are very different, we can modify each lobe independently based on the well-established silane and polymer chemistries. Therefore, both interfacial and compositional asymmetries can be present simultaneously on these dimers, which further enable us to study the synergic effects of both asymmetries on particle propulsion and emulsifying properties of the hybrid dumbbells.

Synthesis of hybrid dumbbells with combined compositional and interfacial asymmetries

249th National Meeting (2015)

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