Influence of mesoporous diatomite on atom transfer radical random copolymerization of styrene and methyl methacrylate: Kinetics and thermal studies

In situ copolymerizations of styrene and methyl methacrylate (MMA) by atom transfer radical random copolymerization in the presence of mesoporous diatomite were performed to synthesize various poly (styrene-co-methyl methacrylate)/diatomite composites. Special characteristics of the mesoporous diatomite were evaluated by X-ray fluorescence, thermal gravimetric analysis (TGA), transmission electron microscope, and nitrogen adsorption/desorption isotherm. Conversion and molecular weight determinations were carried out using gas chromatography and size-exclusion chromatography, respectively. Due to the pendant hydroxyl groups on the surface of the diatomite platelets and polarity change of the reaction medium, addition of 3 wt% mesoporous kieselgur platelets leads to increase of conversion from 69% to 81%. In addition, polydispersity index values of the poly (styrene-co-methyl methacrylate) chains increases from 1.14 to 1.39 by addition of 3 wt% mesoporous diatomite platelets. Increasing the thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 66.4°C to 72.5°C by adding 3 wt% of mesoporous diatomite platelets.