Thermal Behavior of Polystyrene-Silica NanocompositesPublic Deposited
The formation of covalently grafted polymer brushes on silica (SiO2) nanoparticles was achieved by surface-initiated reversible additionfragmentation chain transfer (si-RAFT) polymerization. RAFT initiator was first attached onto the surface of silica nanoparticles and then examined by ultraviolet-visible spectroscopy (UV-vis) analysis. From the resulting RAFT initiator-modified SiO2 nanoparticles, polymer chains can be reliably grown from styrene derivatives having various halide groups (e.g., F, Cl, Br). These polymer chains were found to be narrowly dispersed by gel permeation chromatography (GPC). Differential scanning calorimetry (DSC) analysis of the polymer-SiO2 nanocomposites showed a much higher glass transition temperature (Tg) than those of bulk polystyrene derivatives, consistent with previously observed data for polystyrene-SiO2 nanocomposites. Within a reasonable range of molecular weight, it appears that polymer chains will gain thermal stabilities when being confined in nanoscale environments, such as being tethered to the surface of the SiO2 nanoparticles.