Enhancing Initiation Efficiency in Metal Free Surface Initiated Atom Transfer Radical Polymerization (SI ATRP)
Well defined polymer inorganic hybrid materials were prepared via metal free surface initiated atom transfer radical polymerization (SI ATRP) with 10 phenylphenothiazine (PhPTZ) as the photocatalyst and 2 bromo 2 phenylacetate initiator tethered to silica surfaces. Initiation efficiency and, hence, graft density were significantly enhanced by this very reactive initiator. The polymerization kinetics, effect of initiator structures, particle sizes, and catalyst concentrations were investigated. Well defined hybrid particles were prepared at a low catalyst concentration (0.02 mol or 0.1 mol to monomer) Poly(methyl methacrylate) (PMMA) with number average molecular weight of 3.65 x 104, dispersity of 1.43, and graft density of 0.60 chain/nm2 was grafted from the surface of silica nanoparticles. The hybrid materials were characterized with size exclusion chromatography (SEC) thermogravimetric analysis (TGA) dynamic light scattering (DLS) and transmission electron microscopy (TEM)