Surface activity and light scattering investigation for some novel aromatic polyester amine surfactants

The preparation of nine novel nonionic polymeric surfactants based on ethoxylated aniline, 2-amino benzene thiol and benzene sulphonamide was described. The number of ethylene oxide units was 2, 10 and 20. The prepared surfactants were characterized by determining their molecular weights and polydispersity by the GPC and also by nitrogen content. Surface tension as a function of concentration of the surfactants in the aqueous phase was measured at 25, 35, 45 and 55 °C using the drop volume tensiometer. From these measurements, the critical micelle concentration (CMC), the maximum surface excess concentration (Γmax), minimum area per molecule (Amin), the effectiveness of surface reduction and the efficiency (pc20) were calculated. The thermodynamic parameters of micellization (ΔGmic, ΔHmic, ΔSmic) and of adsorption (ΔGad, ΔHad, ΔSad) for those nonionic polyester surfactants were also calculated. The static light scattering was used to determine the aggregation number (N°), while the dynamic light scattering provides the hydrodynamic radius of the micelle (RH) and the diffusion coefficient at different surfactant concentrations. The values of RH at different concentrations were used to determine the critical micelle concentration (CMC) giving results that are comparable to those obtained by the surface tension measurements.