Surface tension studies of binary and ternary mixtures of tetradecyltrimethylammonium bromide, ditetradecyldimethylammonium bromide and synperonic PE/F68

Abstract

The binary mixtures of the nonionic copolymer Synperonic PE/F68 with the cationic surfactants tetradecyltrimethylammonium bromide (TTAB) and/or the double chain ditetradecyldimethylammonium bromide (di-TDAB) were studied. Mixtures of the three surfactants were also studied. Surface tension studies, using the Wilhelmy plate method, were made. Synergy as well as time dependent hindrance effects were found. The minimum equilibrium surface tension value found, was that obtained for single di-TDAB. At concentrations below cmc, clusters were formed (critical aggregation concentration). Synperonic PE/F68, a very hydrophilic compound, minimized the electrostatic repulsion between the positively charged headgroups of the cationic surfactants. The adsorption constants continuously decreased with time. The results were compared with previous ones, using binary mixtures of some double cationic surfactants with Pluronic F68 and/or hydroxypropylmethylcellulose (HPMC). The observed differences were attributed to the higher hydrophilicity of Synperonic PE/F68.