Spherical mesoporous silica nanoparticles/tailor-made polystyrene nanocomposites by in situ reverse atom transfer radical polymerization

Abstract

Spherical mesoporous silica nanoparticles (MCM-41)/tailor-made polystyrene nanocomposites were synthesized by in situ reverse atom transfer radical polymerization. Characteristics of spherical MCM-41 nanoparticles were evaluated by nitrogen adsorption/desorption isotherm and X-ray diffraction. Morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. Addition 3 wt% of MCM-41 nanoparticles results in a decrease in conversion from 89 to 53%. Similar reduction behavior is also observed for molecular weight of the nanocomposites. However, polydispersity indices (PDI) values increase from 1.42 to 2.07 by the only 3 wt% addition of MCM-41 nanoparticles. A peak around 4.1 ppm which originates from hydrogen atom of terminal units of polymer chains in 1H NMR spectra in combination with low PDI values can appropriately demonstrate the living nature of the polymerization. Thermogravimetric analysis shows that thermal stability of the nanocomposites is higher than the neat polystyrene and increases by increasing MCM-41 nanoparticles content. Glass transition temperature decreases by the addition of MCM-41 nanoparticles loading as revealed by differential scanning calorimetry results.