Adsorption of cationic polyacrylamide at the cellulose-liquid interface: a neutron reflectometry study.
The layer thickness and density of high molecular weight cationic polyacrylamide (CPAM) adsorbed at the cellulose-water interface was quantified by neutron reflectometry. The thickness of a full monolayer of CPAM of constant molecular weight (13 MD) but different charge densities, adsorbed with or without NaCl (10(-3) M), was studied. Thin cellulose films (40±7 Å) of roughness <10 Å 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 wt%) and the hydrolysis time in sodium methoxide. The adsorption thickness of CPAM (40% charge 13 MD) at the solid-D2O interface was 43±4 Å on cellulose and 13±2 Å 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 Å at 5%). Addition of 10(-3) M NaCl 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 NaCl is much thicker (89±11 Å 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.
BioPRIA-Bioresource Processing Research Institute of Australia, Department of Chemical Engineering, Monash University, Australia.
Jielong
J
Su
Australian Nuclear Science and Technology Organisation (ANSTO), Australia.
Christopher J
CJ
Garvey
Australian Nuclear Science and Technology Organisation (ANSTO), Australia.
Stephen
S
Holt
School of Chemistry, Monash University, Australia.
Rico F
RF
Tabor
Department of Material Engineering, Monash University, Australia.
Bjorn
B
Winther-Jensen
BioPRIA-Bioresource Processing Research Institute of Australia, Department of Chemical Engineering, Monash University, Australia.
Warren
W
Batchelor
BioPRIA-Bioresource Processing Research Institute of Australia, Department of Chemical Engineering, Monash University, Australia. Electronic address: Gil.Garnier@Monash.edu.
Gil
G
Garnier
D000180:Acrylic Resins / Q000737:chemistry*; D000327:Adsorption; D002412:Cations / Q000737:chemistry; D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry* / Q000648:ultrastructure; D004573:Electrolytes / Q000737:chemistry; D006868:Hydrolysis; D009502:Neutrons; D053838:Scattering, Small Angle; D013499:Surface Properties; D014961:X-Ray Diffraction; D000099166:Polyacrylamides
D000180:Acrylic Resins; D002412:Cations; D002482:Cellulose; D004573:Electrolytes; D000099166:Polyacrylamides; C005062:acetylcellulose
Adsorption; CPAM; Cellulose; Polylelectrolyte; Polymer layer; Reflectometry; Solid–liquid interface