Influence Of Functional Group Of The Polymer
INFLUENCE OF FUNCTIONAL GROUP OF THE POLYMER
ON THE CHANGES OF THE STRUCTURE OF ITS MACROMOLECULE AT TiO2 /SOLUTION INTERFACE
S. Chibowski, M. Paszkiewicz
Department of Radiochemistry and Colloid Chemistry,
Faculty of Chemistry, Maria Curie-Skłodowska University,
Pl. M. Curie-Skłodowskiej 3, 20-031 Lublin, Poland
Stability and destabilization of dispersed systems obtain increasing meaning in practice. From this reason, mechanisms that rule these phenomena are widely studied. Polymer compounds are applied as stabilizers or flocculants. From numerous group of polymers, essential meaning have polyethylene glycols (PEG), polyvinyl alcohols (PVA), polyacrylic acids, polyacrylamides and similar compounds. That is why the model studies are often performed on their influence on the physicochemical and electrochemical parameters of solid suspensions in polyelectrolyte solutions.
In the performed examinations, an influence of the different number of acetate groups, present in the PVA macromolecule, on the adsorption and electrical properties of the interface metal oxide/polymer solution was determined. Also was an influence of the PEG molecular weight, on the adsorption and electrical properties of TiO2/solution interface. Main factors, responsible for the observed changes of zeta potential and surface charge of titania were determined, basing on the obtained data. It was proved that changes of the ion structure of Stern layer depend on the molecular weight of PEG whereas for PVA these changes are also connected with the number of acetate groups (degree of hydrolysis) present in macromolecule as well as its conformation. The possible mechanism, responsible for changes of zeta potential due to pH and molecular weight changes, was proposed on the base of determined values of surface charge difference (Δσ0) and of diffuse layer charge difference (Δσd) in the presence and absence of the polymer. Using potential zeta changes, in the presence and absence of the polymer, the thickness of the adsorption layer /δ/ of polyvinyl alcohol on the surface of
titania was calculated. Obtained data confirmed significant influence of acetate groups on /δ/ value, and thus conformation of the polymer chain at the interface of titania.The distinct influence of the PEG molecular weight was also noticed on the values of the determined adsorption layers /δ/.
The comparison of the structures of macromolecules in the solution and at the solid/solution interface was made. From the obtained dependencies some changes of shape and dimension of the polymer coils were proposed for bulk and interface.
Related articles::