The effect of temperature on the adsorption and conformation of polyacrylic acid macromolecules at the ZrO2-polymer solution interface

The effect of temperature on the size of adsorption as well as the structure and thickness of the adsorption layer of polyacrylic acid (PAA) on the surface of zirconium (IV) oxide was analysed. Adsorption, electrokinetic and viscosity measurements indicated that the conformation of polymer chains undergoes significant changes as the temperature rises, Within the range of temperatures studied (15-40 degreesC), the structure of adsorbed macromolecules changes from polymer coils at 15 degreesC to conformation with significant loops and tails stretching perpendicular to the surface of the solid at 40 degreesC. The interaction between PAA chains and ZrO2 surface at 15 degreesC is likely of a predominant dispersion character, and when the temperature rises, the contribution of a hydrogen bridge type of interaction becomes more noticeable. In order to confirm the above adsorption mechanism of polyacrylic acid on the surface of zirconium oxide, the expansion coefficients for its macromolecules in an aqueous solution were calculated. Some parameters that describe the PAA chain in the bulk of the liquid phase and on the surface of the solid were also determined. This constituted the basis for determining the characteristics of the conformation of macromolecules passing from the solution onto the metal oxide surface. (C) 2004 Elsevier B.V. All rights reserved.