Surface activity and association behavior of nonaoxyethylene n-dodecylether in aquo amino acid medium: Tensiometry, small-angle neutron scattering, dynamic light scattering and viscosity studies

Study on the Effects of Biologically Active Amino Acids on the Micellization of Anionic Surfactant Sodium Dodecyl Sulfate (SDS) at Different Temperatures

The micellar properties of the anionic surfactant, sodium dodecyl sulfate (SDS) are modified by the biologically active amino acids. Amino acids (AAs) have experienced a variety of interactions and are proposed to influence SDS micelles due to their nominated hydrophobic interactions. The present study determines the critical micellar concentration (CMC) of SDS in aqueous solutions as well as in amino aqueous solutions. Three amino acids (glutamic acid, histidine, and tryptophan) are considered here. The conductometric measurements were carried out using a wide range of SDS concentrations at different temperatures. Surface tension experiments have also been applied to estimate many surface parameters including surface excess concentration (Γmax), surface occupied area per surfactant molecule (Amin), surface tension at CMC (γcmc), surface pressure at CMC (Πcmc) and Gibbs free energy of adsorption (∆Gads°), enthalpy ∆Hm° and the critical packing parameter (CPP). Interestingly, CMC values of SDS in water and in aqueous amino acids estimated by the surface tension method are comparable with the corresponding values obtained by the conductance method. The thermodynamic parameters of SDS micellization were also evaluated in both presence and absence of AAs. The additives of AAs work to reduce the CMC values, as well as the SDS thermodynamic parameters. This reduction is highly dependent on the hydrophobicity of the AA side chain. Negative values of ∆Gm°, ∆Hm° elucidate that micellization of SDS in the presence of amino acids is thermodynamically spontaneous and exothermic. The outcomes here might be utilized for pharmaceutical applications to stabilize proteins and inhibit protein aggregation.

Interactions of Cationic, Anionic and Nonionic Surfactants with Cresol Red Dye in Aqueous Solutions: Conductometric, Tensiometric, and Spectroscopic Studies

The interaction of cresol red (CR) with cetylpyridinium bromide (CPB), sodium dodecyl sulphate (SDS), and Triton X-100 (TX-100) was studied in aqueous solutions employing conductometric, tensiometric, and spectroscopic methods. Various micellar and interfacial parameters were calculated in absence and in presence of CR. The interactions suggest the formation of a CR-CPB adduct, an association of CR with the micelle of TX-100 while no adduct is formed between CR and SDS. Appreciably low critical micelle concentration, CMC value of TX-100 compared with those of CPB and SDS in pure water and drastic reduction of CMC of CPB (about one-twelfth of its value in pure water) than SDS and TX-100 in the presence of CR were observed. Higher negative values of Gibbs free energy of micellization, ΔG m 0, for all the three surfactants indicate that micellization process is spontaneous. The values of maximum surface excess concentration, Γ max, and minimum area per molecule, A min, suggest that in the presence of CR, the air-solution interface is closely packed and the orientation of surfactant molecules is almost perpendicular to the surface. UV-visible spectra suggest the formation of ion-pair complex between the dye CR and the monomers of CPB in the pre-micellar region, while above the CMC a breaking up of the ion-pair complex takes place and the dye is solubilized in the micelles of CPB. In the case of SDS the absorption spectra indicate weak interaction between CR and SDS molecules formation of H-bonding, short range dispersive forces, and hydrophobic interactions between CR and TX-100 molecules in the solution.

Synergistic mechanism between laurel alkanolamide and hydrophobically associating polyacrylamide in solutions with high salinity

The hydrophobic interaction between laurel alkanolamide micelles and hydrophobically associating polyacrylamide enhances the formation of network structure and the viscosity of the mixed solution increases in a large electrolyte concentration range.

Monitoring the aggregation behaviour of self-assembling polymers through high-resolution ultrasonic spectroscopy

Poloxamer 407 is a well-known self-assembling polymer with a wide range of temperature- and concentration-dependent phase behaviour, such as micellization and gelation. This work was carried out to demonstrate the potential of high-resolution ultrasonic spectroscopy in evaluating aggregation-deaggregation behaviour of self-assembling polymers. In order to achieve this objective, six different concentrations of Poloxamer 407 water dispersion were prepared and analysed between 5 and 35 degrees C using ultrasonic spectroscopy. For comparison, the same samples were also analysed by the DSC technique. The results showed that polymer aggregation process can be successfully monitored using both ultrasonic parameters of sound speed and attenuation. Furthermore, good agreement with DSC data was observed in terms of characteristic transition temperatures and also in terms of micellization kinetics and related parameters.