Investigating the effect of pristine and modified silica nanoparticles on the kinetics of methyl methacrylate polymerization

To study the effect of silica nanoparticles on the kinetics of methyl methacrylate free radical polymerization, a number of batch polymerizations were performed using pristine and methacrylate-modified silica nanoparticles at 75 degrees C. In addition, effect of temperature was investigated on the kinetics of polymerization with 1 wt% loading of pristine nanoparticles. Monomer conversion, reaction rate, molecular weight and polydispersity index (PDI) of each polymerization were monitored during polymerization. According to results, no considerable change was obtained on the polymerization kinetics by introduction of any type of nanoparticles, while there is an optimum loading value in which the polymerization rate reaches its maximum level. A similar trend is observed for molecular weight of free chains; however, increasing silica content results in increased PDI values. Also, polymerizations rate is slower for batches containing modified nanoparticles. For chains which are grafted on the surface of modified nanoparticles, molecular weight and PDI values increase by increasing nanoparticle content. (C) 2011 Elsevier B.V. All rights reserved.