Mixtures of ethyl(hydroxyethyl)cellulose (EHEC) and Sodium Dodecyl Sulfate (SDS) were investigated using surface tension, conductivity and viscosity measurements in aqueous solutions. The parameters of the surfactant to polymer association processes such as the critical aggregation concentration (cac) and saturation of the polymer by SDS (psp) were determined from the plots of surface tension and specific conductivity versus surfactant concentration. Through the final results we see that there was no specific link of polymer with the surfactant, implying therefore a phenomenon of only cooperative association.

Mixed-micelle formation between sodium chlolate (NaC) and the anionic surfactant sodium dodecanoate (SDoD) in Tris-HCl buffer solutions, pH 9.00, varying the molar fraction of the surfactants, was investigated by means of electrical conductivity and steady-state fluorescence of pyrene. The critical micelar concentration (cmc) was measured from the equivalent conductance versus the square root of the molar surfactant concentration plots and the regular solution theory (RST) was used to predict the mixing behavior. The I1/I3 pyrene ratio-surfactant concentration plots were used as an additional technique to follow the behavior and the changes in the micropolarity of the mixed micelles.

Neste trabalho foram construídos eletrodos seletivos para o surfactante dodecilsulfato de sódio (SDS) e para brometo, respectivamente, eletrodo indicador e de referência, para medidas potenciométricas. Os eletrodos foram utilizados em solução de SDS e em mistura de SDS e poli(oxietileno) (PEO). Os perfis de potencial da célula (E) versus a concentração de SDS, na ausência e em presença de 0,5% de PEO, são sensíveis ao processo de associação cooperativa entre SDS e PEO e indicativos de parâmetros como concentração crítica de agregação, cac, e concentração de saturação do polímero, psp. Os parâmetros obtidos por esta metodologia estão em concordância com os obtidos por técnicas clássicas como a de tensão superficial e a de condutividade elétrica.

Surfactant-selective electrodes to sodium dodecyl sulfate (SDS) monomer and bromide were constructed, respectively, electrode idicator and reference electrode. The electrodes were tested for solutions of SDS and in mixture of SDS and poly(ethylene oxide) (PEO). The profiles obtained measuring the potential (E) versus SDS concentration in the presence of 0.5% PEO are sensitive to polymer-surfactant parameters such as the onset of cooperative association of SDS to PEO, the critical aggregation concentration (cac), and the polymer saturation by SDS monomers (psp). The obtained parameters are in agreement with those values found by surface tension and electrical conductivity.

Molecular probe techniques have made important contributions to the determination of microstructure of surfactant assemblies such as size, stability, micropolarity and conformation. Conductivity and surface tension were used to determine the critical aggregation concentration (cac) of polymer-surfactant complexes and the critical micellar concentration (cmc) of aqueous micellar aggregates. The results are compared with those of fluorescent techniques. Several surfactant systems were examined, 1-butanol-sodium dodecylsulfate (SDS) mixtures, solutions containing poly(ethylene oxide)-SDS, poly(vinylpyrrolidone)-SDS and poly(acrylic acid)-alkyltrimethylammonium bromide complexes. We found differences between the cac and cmc values obtained by conductivity or surface tension and those obtained by techniques which use hydrophobic probe.