Reverse Atom Transfer Radical Polymerization of Styrene in the Presence of Functionalized Silica Aerogel Nanoparticles

Abstract

Abstract Pristine silica aerogel nanoparticles surface was functionalized with 3-(trimethoxysilyl)propyl methacrylate (MPS). Then, the resultant functionalized nanoparticles were used in grafting through polymerization of styrene by reverse initiation technique for atom transfer radical polymerization. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the synthesized nanoparticles. Evaluation of size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography respectively. Addition of MPS-functionalized nanoparticles by 3 wt % results in a decrease of conversion from 98 to 81%. Molecular weight (M n) of the free polystyrene chains decreases by adding 3 wt % modified silica aerogel nanoparticles; however, polydispersity index (PDI) values increases from 1.31 to 1.92. Although PDI values of attached polystyrene chains are increased, M n values reveal an increment by adding silica aerogel nanoparticles. A peak around 4.1 ppm which originates from hydrogen atom of terminal units of polystyrene chains in proton nuclear magnetic resonance spectra can demonstrate the living nature of the polymerization. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry also shows a decrease in glass transition temperature by increasing modified silica aerogel nanoparticles.