The swelling of PDMAEMA and PMETAI brushes was first investigated by ellipsometry. Brushes were generated on silicon substrates displaying a thin silicon oxide layer (native oxide, plus further oxidation via plasma for 10 min). For ellipsometry measurements, thin silicon wafers were used, whereas samples prepared for neutron reflectometry were generated on silicon blocks (15 mm thick) to enable the beam to propagate and reflect from the silicon side. In both cases, identical protocols were used to plasma treat the silicon surface, deposit ATRP initiator monolayers and polymer brushes were generated in comparable conditions (an in-house designed reaction chamber was used to generate brushes from the surface of silicon blocks, under inert atmosphere, as described in the methods). The ellipsometric thicknesses of dry brushes generated from silicon wafers and blocks were comparable, within 2 nm.