The impact of nucleic acid materials adsorption to polymer brushes on the architecture of the coating was investigated next. First, the thickness and swelling of PDMAEMA brushes were investigated using ellipsometry (Figure ). Brush swelling in different buffers was found to be comparable, although a slight increase in PBS and 150 mM sodium chloride was observed compared to deionised water (Figure ), in agreement with previous reports . Upon complexation of nucleic acid materials in PBS, negligible changes in thicknesses were observed, ranging from 2-7 % of the initial swollen thickness, with ssRNA oligos displaying slightly higher increases in thicknesses (Figure and). Considering the density of PDMAEMA and the dry thickness of the brushes presently studied, the surface density of the brushes was determined as 3.78 µg/cm 2 . This indicates that the oligonucleotides surface densities achieved on PDMAEMA brushes are comparable or modestly lower (50%, Figure ) to the surface density of the PDMAEMA brush achieved. Therefore, the weak increase in swollen thickness observed upon complexation strongly suggests the deep penetration of nucleic acid materials within the brush structure, although the poor z-resolution of ellipsometry does not enable resolving associated architectures. Similarly, the complexation of nucleic acid materials within PMETAC brushes had a negligible impact on the swollen ellipsometric thickness of these coatings (Supplementary Figure ; note that PMETAC brush swelling was found to be slightly lower than that of PDMAEMA brushes, presumably due to the partial hydration of these coatings in air ). a series of their dry profiles were collected. Dry brushes exhibited architectures comparable to those previous reported via neutron reflectometry (Supplementary Figure and S1), with thicknesses consistent with ellipsometric measurements. The brushes prepared for complexation were then characterised prior to binding first, using three PBS media displaying different contrasts (D2O, H2O, and PDMAEMA-contrast matched with and scattering length density, SLD, of 0.89 ×10 -6 Å -2 ; details of the SLDs used for fitting of neutron reflectivity data can be found in Supplementary Table ).