Effect of the solid pore size on the structure of polymer film at the metal oxide/polyacrylic acid solution interface – Temperature impact

• Temperature effect on PAA adsorption on various metal oxides was determined.
• The following adsorbents: ZrO2, Al2O3, SiO2, CPG were used.
• The temperature increase leads to the increase of macromolecule size.
• Polymer adsorption increases with temperature rise for Al2O3, SiO2, CPG systems.
• Adsorption minimum at 25–30 °C was observed for zirconia.

The goal of the study was to determine the effects of adsorbent type and its pore size on the polyacrylic acid (PAA) adsorption mechanism on the solid surface in the temperature range 15–40 °C. The following metal oxides were applied: aluminum (III) oxide, silicon (IV) oxide, zirconium (IV) oxide and controlled porosity glass (CPG). PAA adsorption characteristics at the metal oxide-aqueous solution interface was proposed based on the data obtained from the techniques: spectrophotometry, viscometry and potentiometric titration. They allowed the determination of the following parameters: the amount of adsorbed polymer, the linear dimensions of polymer chains in the solution, the thickness of the polymer adsorption layer, as well as the surface charge density of the adsorbent in the absence and presence of PAA. It was shown, that the adsorption of polyacrylic acid on the metal oxide surface proceeds through both electrostatic and hydrogen bridge interactions. Moreover, the temperature increase leads to the increase of macromolecule size, which influences the polymer adsorbed amount and the structure of its adsorption layer. It results in the increase of polymer adsorption with the temperature rise in the case of alumina, silica and CPG. For zirconia the adsorption minimum in the temperature range 25–30 °C was obtained. Such behaviour of the investigated systems is caused by various pore size of the applied metal oxides.

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