Pickering emulsion polymerization of poly(ionic liquid)s encapsulated nano-SiO₂ composite particles with enhanced electro-responsive characteristic

Poly(ionic liquid)s (PILs) encapsulated nano-SiO₂ composite particles were synthesized by a Pickering emulsion polymerization and used as stimuli-responsive electorheological (ER) particles, which showed enhanced electro-responsive effectiveness and temperature stability. Methacryloxypropyltrimethoxysilane modified nano-SiO₂ particles with size of 15 nm were used as solid surfactant, which could not only help to form emulsion droplets of IL monomer but also immerse into droplets to form nanocomposite particles after polymerization. The morphology of the nanocomposite particles was characterized by scanning electron microscopy and transmission electron microscopy, while the chemical structure was analyzed by thermogravimetric analysis and Fourier transform infrared spectroscopy. Under electric field, ER property of the nanocomposite particles when dispersed in insulating oil was characterized by temperature-modulated rheology. Through comparing with pure PILs particles, we found that introducing nano-SiO₂ into PILs particles could significantly suppress the excessive growth of leaking current density with increasing temperature and improve the electro-responsive ER effectiveness and temperature stability of ER property. Dielectric spectra analysis indicated that nano-SiO₂ could act as cross-linking points to suppress the thermally promoted segment relaxation and improve the activation energy of the ion transport in PILs matrix, and this should be responsible for the enhanced electro-responsive ER effectiveness and temperature stability of PILs encapsulated nano-SiO₂ composite particles.