Poly(styrene)/silica hybrid nanoparticles prepared via ATRP as high-quality fillers in elastomeric composites

Organic-inorganic hybrid nanoparticles of poly(styrene) (PSt) and fumed silica have been successfully synthesized via atom transfer radical polymerization (ATRP) and investigated as fillers for styrene-butadiene rubber (SBR). On the one hand, they were prepared by using the grafting from methodology, in which an ATRP initiator was covalently attached onto the silica and subsequently, PSt chains were grown directly from the surface. On the other hand, the grafting to methodology was used to attach onto the silica, a carboxylic acid end-functionalized PSt, previously synthesized by ATRP. Then, these hybrid nanoparticles could be easily incorporated as fillers into SBR elastomeric matrices by conventional methods employed in rubber technology. The properties of these composites, analyzed by strain sweep tests, scanning electron microscopy, dynamic mechanical measurements, H-1 low field double quantum NMR and tensile strength tests, were compared with those obtained using unmodified silica as the filler. The presence of silica particles coated with PSt brushes deeply affects the dynamic and physical response of the elastomer composites prepared, due to the high dispersion and excellent compatibility between the SBR matrix and PSt coated silica. Moreover, the experimental results also indicated that hybrid nanoparticles synthesized by the grafting from methodology are much better for filler applications in the SBR matrix than those obtained by using the grafting to methodology.