In this study, the architecture of polycationic brushes and their complexes with RNA oligos is investigated via combined ellipsometry and neutron reflectometry. Subsequently, 120 mL of DMAEMA solution was transferred to reaction vessels under inert atmosphere, via a syringe. The polymerization was stopped after 39 and 10 min of reaction, for 30 and 10 nm brushes generated from undiluted initiator monolayers, respectively. For low density brushes, the polymerisation time was 39 min, to achieve comparable chain lengths to those achieved for high density brushes. In each case, the polymerisation was ended by immersing the coated substrates in deionized water followed by washing with copious amounts of ethanol and drying under a nitrogen stream. The dry thickness of the PDMAEMA brush was subsequently determined via ellipsometry. The swelling of brushes in deionised water was studied via in-situ ellipsometry.