EFFECT OF CARBON NANOTUBES ON THE KINETICS OF IN SITU POLYMERIZATION OF METHYL METHACRYLATE

Abstract

The effect of carbon nanotubes on the kinetics of free radical polymerization of methyl methacrylate (MMA) was investigated. To do this, pristine, acid treated, alcoholic and methacrylate-modified carbon nanotubes with different loadings were used and Conversion, molecular weight and polydispersity index (PDI) of all samples were monitored during polymerization. The results show that carbon nanotubes induce an induction time to polymerization system which is independent of modification system while decrease in monomer conversion can be improved by developing organic moieties on surface. Molecular weight and polydispersity index for free and attached-on-surface chains were studied separately and different kinetics behaviors were observed for them. Molecular weight of free chains was increased by adding carbon nanotubes while more modified nanotubes resulted in much increased molecular weight. On the other hand, more system stability of more modified nanotubes, which was tested using UV-Visible spectra, resulted in higher molecular weights. Adding more nanotubes in the case of MMA-modified nanotubes caused to determine an optimum loading value to reach maximum molecular weight of free chains which was ascribed to system stability according to UV-Visible results. In this optimum loading value, free chains had minimum PDI value. However, increasing carbon nanotubes content led to decreased molecular weight of attached chains while PDI values increased because of shielding effect as physical phenomenon.