Water content gradually increased, away from substrate towards the bulk aqueous phase, perhaps indicating an increased density close to the substrate (brushes, and more generally polymer chains grown by ATRP are typically associated with high polydispersities, proposed to result in short dead chains with high density close to the surface ), or potentially reflecting a higher pH within the brush core, or reduced ionisation level . Indeed, a reduced local pH would be associated with a neutral brush with an SLD close to 0.913 × 10 -6 Å -2 , whereas protonated brushes are expected to display an SLD of 1.67 × 10 -6 Å -2 in D2O. Low density brushes (s of 0.1 chains/nm 2 ) displayed more gradual increase in SLD and associated changes in hydration, reflecting the expected lack of structure and alignment in chains within these coatings. Denser brushes displayed clearer steps in SLD between different layers.