Synthesis of monodispersed polyisoprene–silica nanoparticles via differential microemulsion polymerization and mechanical properties of polyisoprene nanocomposite

Monodispersed polyisoprene–SiO2 nanoparticles were successfully synthesized by a differential microemulsion polymerization of isoprene on silane treated nanosilica. Core–shell morphology was formed consisting of silica as the nano-core encapsulated by polyisoprene (PIP) as the nano-shell, as confirmed by TEM. PIP–SiO2 nanoparticles were produced at 20–60 nm with a narrow size distribution resulting in a reduced nano-SiO2 aggregation in the PIP matrix. The influence of surfactant concentration, monomer/water ratio and SiO2 loading on particle size, monomer conversion as well as grafting efficiency was investigated. The monomer conversion was 87% and the polymer grafting efficiency was as high as 78% at an extremely low surfactant concentration (3 wt.% based on monomer). For rubber applications, the PIP–SiO2 nanocomposite has been used as an effective nano-filler in natural rubber (NR) latex and the NR filled with PIP–SiO2 prevulcanizate clearly showed an improvement in the storage modulus, tensile strength, tensile modulus, and anti-ageing properties.

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► Polyisoprene (PIP)–SiO2 was synthesized via differential microemulsion polymerization.
► PIP–SiO2 nanoparticles were produced at 20–60 nm with a narrow size distribution.
► Core–shell morphology of nano-SiO2 encapsulated with nanosized PIP was achieved.
► Synthetic PIP–SiO2 could be used as novel reinforcing nanofiller in natural rubber.
► PIP–SiO2 filled NR had high mechanical properties and excellent thermal stability.