Study of kinetics and properties of polystyrene/silica nanocomposites prepared via in situ free radical and reversible addition-fragmentation chain transfer polymerizations

A number of batch polymerizations were performed to study the effect of pristine nanoparticleloading on the kinetics of free radical and raft polymerizations and properties of polystyrene/silicananocomposites. to study the kinetics of polymerization, conversion, molecular weight and polydispersityindex (pdi) were monitored during polymerization to investigate the reaction kinetics. according tothe results, adding nanoparticles causes no considerable change in the kinetic curves, while there isan optimum value for nanoparticles loading in which the monomer conversion and molecular weightreaches to its maximum level. however, increasing silica content resulted in an increase in pdi values.in comparison with free radical polymerization, monomer conversion and molecular weight were lowerfor raft polymerization. the prepared samples were characterized by thermogravimetric analysis (tga),dynamic mechanical thermal analysis (dmta), and differential scanning calorimetry (dsc). accordingto tga results, in free radical samples, one stage of degradation related to the random chain scission isobserved while degradation of raft nanocomposites has occurred in two steps due to decomposition ofraft moieties and random chain scission. also, the best improvement of mechanical and thermophysicalproperties is achieved for nanocomposites containing 5 wt% silica nanoparticles.