Surface Properties of Modified Poly(4-vinylpyridine)

Abstract

ABSTRACTPoly(4-vinyl-pyridine) was quaternized at 80% with octyl and dodecyl bromide. Surface properties of very dilute solutions in water were studied at various temperatures. Interfacial tension measurements were carried out according to the Wihelmy method. In all the studied systems, the interfacial tension decreased with the polyelectrolyte concentration as the side chain length decreased. According to the Gibbs–Szyszkowski equation, the excess interfacial concentrations, Γ, and areas covered by a monomer unit, σ, were determined. The standard free energy, , of the adsorption process was found to be more negative as the temperature increased. The data also revealed that the adsorption process was governed by two contrasting factors; the tendency of the polyelectrolyte to migrate to the surface and the opposing trend that stabilizes the polyelectrolyte in the bulk by minimizing the hydrophobic interactions of the side aliphatic chains. The surface tension behavior showed that the polyelectrolyte containing 8 carbon atoms in the side chain was more active at the surface than the polyelectrolyte with 12 carbon atoms, but the values suggested that the polyelectrolyte containing larger lateral chains were more stable at the surface. The dependence of the interfacial tension with temperature suggested that entropy was the driving force factor determining the adsorption process.