No abstract

Four different fluoride, chloride, bromide, and nitrate cationic polyelectrolytes were prepared. Their electrolytic conductivity in aqueous dilute solution was investigated. The results show a remarkable increase, with dilution being practically constant down to limiting concentration. The limiting equivalent conductivity Λ° follows the order $\[ {\rm F}^ - \gg {\rm Cl}^ - > {\rm Br}^ - \approx {\rm NO}_3^ - \]$ The distances between neighboring charges calculated from experimental data are in good agreement with those calculated geometrically according to Manning's definition. The results are mainly dependent on the assumption that Br− and NO3− interact in a similar manner with the cationic charges on the polyion. This phenomenon also has been observed in cationic micelles.

The Du Noüy method has been employed to study the interfacial properties of poly(4‐vinylpyridine) N‐n‐alkyl quaternized with hexyl, octyl and decyl bromide, at the chloroform/water interface. The interfacial tension is highly dependent on the hydrophilic–hydrophobic balance between the pyridinium group and the length of the polyelectrolyte side aliphatic chain. The excess interfacial concentration, Γ, is determined according to the Gibbs–Szyszkowski equation. The areas covered by monomer unit at the interface, σ, are smaller than those reported for low molecular weight amphipathic molecules. The linear dependence of $\Delta G_{\rm{ads}}^{\rm{o}}$ with the number of carbon atoms on the side‐chain allows the determination of a contribution of just 0.13 kJ for each methylene lateral group and −36 kJ for the vinylpyridinium bromide contributions to $\Delta G_{\rm{ads}}^{\rm{o}}$. The dependence of the interfacial tension on temperature suggests that the entropy is the main factor determining the adsorption process. Copyright © 2003 Society of Chemical Industry

Partition constants for several aliphatic alcohols between water and micellar phases were determined using ultrafiltration and dialysis. Results indicated that the micellized concentrations of the long-chain alcohol followed a Langmuir adsorption isotherm type of profile. Association of pentanol and hexanol with cylindrical micelles induces an increase in size and in dissociation degree (a), followed by a micellar breakdown. These changes can be explained in terms of the number of alcohol molecules per micelle.

The mean ion activity coefficient, (γ±)px/(γ±)salt for different high‐linear charge density cationic polyelectrolyte fluoride, bromide, chloride and nitrate has been determined. The order found is: F− > CI− ≧ Br− > NO −3. The results obtained with added nitrate were compared with those predicted by Iwasa, Guéron, and Weisbuch and Manning's models. The latter presents the best agreement for polyion chloride and bromide. It was possible to establish the most probable microconfiguration for the polyions studied here. Manning's theory gives a moderate agreement for polyion fluoride values compatible with a lower charge density than for polyelectrolyte chloride and bromide.