The layer thickness and density of high molecular weight cationic polyacrylamide (CPAM) adsorbed at the cellulose-water interface was quantified by neutron retlectometry. The thickness of a full monolayer of CPAM of constant molecular weight (13 MD) but different charge densities, adsorbed with or without NaCI (10(-3) M), was studied. Thin cellulose films (40 +/- 7 A) of roughness <10 angstrom were produced by spin -coating a cellulose acetate-acetone solution and regenerating by alkaline hydrolysis. Film smoothness was greatly improved by controlling the concentration of cellulose acetate (0,13 wff) and the hydrolysis time in sodium methoxide. The adsorption thickness of CPAM (40% charge 13 MD) at the solid-D20 interface was 43 4 A on cellulose and 13 +/- 2 A on silicon, an order of magnitude smaller than the CPAM radius of gyration. At constant molecular weight, the thickness of the CPAM layer adsorbed on cellulose increases with polymer charge density (10 1 A at 5%). Addition of 10-3 M NaCI decreased the thickness of CPAM layer already adsorbed on cellulose. However, the adsorption layer on cellulose of a CPAM solution equilibrated in 10-3 M NaCI is much thicker (89 +/- 11 A for 40% CPAM). For high molecular weight CPAMs adsorbed from solution under constant conditions, the adsorption layer can be varied by 1 order of magnitude via control of the variables affecting electrostatic intra- and inter-polymer chain interactions. Crown Copyright (C) 2015 Published by Elsevier Inc. All rights reserved.