Adsorption Kinetics of cationic Polyelectrolytes studied with Stagnation Point Adsorption Reflectometry and Quartz Crystal Microgravimetry
2008 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 14, 7329-7337 p.Article in journal (Refereed) Published
The effects of charge density, pH, and salt concentration on polyelectrolyte adsorption onto the oxidized surface of silicon wafers were studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry. Five different polyelectrolytes-cationic polyacrylamides of four charge densities and one cationic dextran-were examined. The adsorption kinetics was characterized using each technique, and the adsorption kinetics observed was in line with the impinging jet theory and the theory for one-dimensional diffusion, respectively. The polyelectrolyte adsorption increased with pH as an effect of the increased silica surface charge. A maximum in the saturation adsorption for both types of polyelectrolytes was found at 10 mM NaCl concentration. A significant adsorption also occurred at I M NaCl, which indicated a significant nonionic contribution to the adsorption mechanism. The fraction of solvent in the adsorbed layer was determined to be 70-80% by combining the two analysis techniques. This indicated a loose structure of the adsorbed layer and an extended conformation at the surface, favoring loops and tails. However, considering the solution structure with a hydrodynamic diameter larger than 100 nm for the CPAM and a thickness of the adsorbed layer on the order of 10 nm, the results showed that the adsorption is accompanied by a drastic change in polymer conformation. Furthermore, this conformation change takes place on a time scale far shorter than seconds.
Place, publisher, year, edition, pages
2008. Vol. 24, no 14, 7329-7337 p.
Charge density; Concentration (process); Curve fitting; Electrolytes; Fluid dynamics; Fluid mechanics; Glucose; Nonmetals; Oxide minerals; pH effects; Polyelectrolytes; Polymers; Powders; Quartz; Reflection; Reflectometers; Silica; Silicate minerals; Silicon; Silicon compounds; Silicon wafers; Sodium alloys; Surface charge
Engineering and Technology
IdentifiersURN: urn:nbn:se:kth:diva-6014DOI: 10.1021/la800198eISI: 000257468300042ScopusID: 2-s2.0-47949120059OAI: oai:DiVA.org:kth-6014DiVA: diva2:10585
QC 20100719. Uppdaterad från manuskript till artikel (20100719).2006-06-212006-06-212010-07-20Bibliographically approved