Initiator deposition. ATRP initiators were deposited on silicon or gold substrates. For the deposition on silicon, substrates (freshly treated with air plasma) were immersed in a solution of toluene (30 mL), silane initiator (30 μL) and triethylamine (50 μL), overnight. Deposition on gold was carried out in the same way but in a thiol initiator solution (5 mM, in ethanol). For low density brushes, trimethoxypropylsilane or undecanethiol (for silicon and gold substrates, respectively) were used as unreactive silane/thiol at 20:1 with respect to initiator. Upon deposition, substrates were washed with ethanol and dried with a N2 stream.