Synthesis of PDMAEMA brushes from silica particles

Silica particles (microparticles with average size of 3 μm, and nanoparticles with average size of 300 nm) were functionalised with PDMAEMA brushes. Briefly, 200 mg of silica particles were washed/suspended with anhydrous toluene (4 mL) three times, under inert atmosphere. The particles were then redispersed in anhydrous toluene. Anhydrous triethylamine (200 μL, Et₃N, distilled over potassium hydroxide) and the silane initiator ((3-trimethoxysilyl)propyl 2-bromo-2-methylpropionate, 40 μL) were added to the resulting suspension and the mixture was allowed to react overnight with continuous agitation. Silane initiator-coated particles were washed three times with ethanol and stored in 10 mL water/ethanol (4/1 v/v), at 4 °C, until used for polymerisation. DMAEMA (6.6 g, 42 mmol), bpy (320 mg, 2.05 mmol) and CuBr₂ (80 mmol) were dissolved in water/ethanol 4/1 (v/v; 20 mL). The resulting mixture was degassed for 30 min with argon bubbling whilst stirring prior to the addition of and CuCl (0.082 g, 828 µmol) and further degassing. Polymerisation was allowed to proceed under argon at RT for 20 min to achieve a PDMAEMA brush thickness of 30 nm. To stop the polymerization, the reaction mixture was diluted with deionised water and air was bubble through, until the colour changed from dark brown to blue. PDMAEMA-grafted silica particles were separated via centrifugation, at 3100 × g for 10 min, successively washed with water and ethanol (each time with centrifugation), to remove the catalyst and residual monomer. Resulting particles were stored in after drying, in a fridge.