Abstract
A series of styrene–acrylonitrile (SAN) copolymer nanoparticles were prepared by grafting styrene–acrylonitrile from both aggregated silica and colloidally dispersed silica nanoparticles using atom-transfer radical polymerisation (ATRP). Cross-linking and macroscopic gelation were minimised by using a miniemulsion system. The thermal and mechanical behavior of composites were made from PSAN aggregated silica nanoparticles or colloidally dispersed silica has been examined by Differential scanning calorimetry (DSC) and Dynamic mechanical thermal analysis (DMTA). The filler particles increased the rubbery modulus above the Tg of PSAN considerably and led to a temperature-independent plateau of the modulus between 130 and 240 °C similar to that normally observed for crosslinked amorphous polymers. Covalent attachment of PSAN to the silica nanoparticles, by grafting the polymer from the surface of the silica using atom transfer radical polymerization (ATRP), gave rise to hybrid materials with a comparable elastic plateau. While neat PSAN started to flow and deform irreversibly above 120 °C, the new silica nanoparticle–polymer hybrid materials proved stable up to 240 °C, which was more than 120 °C above the Tg of the polymer. Aggregated silica nanoparticles displayed more affect compared to colloidally dispersed silica.