Synthesis of Ultra-high Molecular Weight SiO2-g-PMMA Particle Brushes

A simple route to synthesize ultra-high molecular weight particle brushes by surface-initiated atom transfer radical polymerization (SI-ATRP) from silica nanoparticles was developed. SiO2-g-PMMA and SiO2-g-PS particle brushes were prepared with different [SiO2–Br]0 concentration of initiating sites on the surface of the nanoparticles. Ultra-high MW (> 106) SiO2-g-PMMA particle brushes with narrow molecular weight distribution (< 1.3) and different grafting densities were synthesized. The grafting density of SiO2-g-PMMA particle brushes decreased with increasing target degree of polymerization. The same conditions were applied to the synthesis of SiO2-g-PS particle brushes. However, due to the lower propagation rate constant of styrene, coupling between SiO2-g-PS particle brushes occurred and also some fraction of unattached homopolystyrene was generated by the thermal self-initiation of styrene, preventing successful synthesis of ultra-high MW SiO2-g-PS particle brushes.