Home List of Titles Adsorption of bilayers and multilayers of cationic and anionic co-polymers of acrylamide on silicon oxide
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/231521
- Adsorption of bilayers and multilayers of cationic and anionic co-polymers of acrylamide on silicon oxide
- Wagberg, Lars; Pettersson, Gunilla; Notley, Shannon
- Silica surfaces were consecutively treated with copolymers of cationic and anionic polyacrylamides (C-PAM and A-PAM, respectively) and the layer-by-layer build-up was continuously monitored with the aid of stagnation point adsorption reflectometry (SPAR). Four different charge densities of the cationic polymer and one charge density of the anionic polymer were studied. The solid substrate used in the investigation was an oxidized Si wafer, the charge of which was varied by performing the measurements at different pH. Adsorption measurements were performed both in deionized water and with a background electrolyte concentration of 0.01 M NaCl. The results show that the adsorption of C-PAM at pH 6 was dominated by electrostatic interactions. However, a significant nonionic contribution to the adsorption of C-PAM on SiO₂ was detected-when the results of adsorption measurements conducted in deionized water and in 0.01 M NaCl were compared. At pH 9, the adsorption of C-PAM onto SiO₂ was found to be geometrically restricted since the adsorption stoichiometry between the polymer charges and the charges on the surface was less than 1 irrespective of the charge of the C-PAM. Adsorption of the A-PAM onto the C-PAM covered surface increases as a function of the adsorbed charges in the first layer. Experiments showed that it was possible to form multilayers of polyelectrolytes on the SiO₂ surface provided the charge of the C-PAM was high enough. The critical charge of the polyelectrolyte for the formation of multilayers was also dependent on the charge of the substrate; that is, the lower the surface charge the higher the critical charge of the C-PAM. The substrate affected the amount of polyelectrolyte adsorbed up to the fifth layer. For further layers there was almost a stoichiometric relationship between the charges of the polyelectrolytes in consecutive layers. Results from studies of the formed multilayers with a quartz crystal microbalance (QCM-D) indicated that there was a close correlation between energy dissipation into the multilayers and a decrease in the adsorption as detected with SPAR. This in turn indicates that a decrease in the reflectometer signal does not necessarily indicate a decrease in adsorption.
- Publication type
- Journal article
- Journal of Colloid and Interface Science, Vol. 274, no. 2 (Jun 2004), pp. 480-488
- Publication year
- FOR Code(s)
- 02 Physical Sciences; 03 Chemical Sciences; 09 Engineering
- Acidity; Acrylic monomers; Adsorption; Anion; Cation; Concentration process; Copolymer; Correlation analysis; Crystal; Deionised water; Density specific gravity; Electricity; Electrolytes; Electrostatic interactions; Energy dissipation; Geometry; Ionization; Oxidation; pH effects; Polyacrylamide; Polyelectrolyte; Positive ions; QCM; Quartz crystal microbalance; Reflectometers; Reflectometry; Silicon dioxide; Sodium chloride; SPAR; Stagnation point adsorption reflectometry; Stoichiometry; Surface charge; Water
- Academic Press
- Publisher URL
- Copyright © 2003 Elsevier Inc. All rights reserved.
- Peer reviewed