Thermal and Physical Ageing Properties of Poly(methyl methacrylate) Silica Nanocomposites

Poly(methyl methacrylate) (PMMA) nanoparticles were prepared by grafting methyl methacrylate from both aggregated silica and colloidally dispersed silica nanoparticles using atom-transfer radical polymerisation (ATRP). Cross-linking and macroscopic gelation were avoided using a miniemulsion system. The thermal and physical ageing behavior of the nanocomposites have been examined by differential scanning calorimetry (DSC). The addition of silica nanoparticles to PMMA can influence its thermal and aging properties. Grafting PMMA-aggregated silica revealed considerable increase in the glass transition temperature, whereas colloidally silica nanoparticles showed only a marginal improvement. Additionally, while dispersing PMMA in colloidal and aggregated silica accelerated physical ageing, grafting to aggregated silica significantly reduced ageing rates.