1,3-Butanediol as a co-solvent for the surfactant solutions

A biphasic solution containing water and precipitated phosphocholine (PC) is presented in order to investigate the consequences of 1,3-butanediol addition on the phase behavior of PC at different 1,3-butanediol concentrations and temperature values. With increasing the concentration of 1,3-butanediol in the mixed solvent at room temperature, the biphasic solution converts into turbid phase, two phase, and finally to a clear phase that is birefringent when viewed between two crossed polarizers. The birefringent phase moves to lower 1,3-butanediol contents at higher temperature values. The birefringent phase was observed via polarizing microscopy, and its rheological parameters were measured with cone plate method. In high 1,3-butanediol contents, solutions with 2.5% of PC behave as a gel with high yield stress value. The micellization of cetyltrimethyammonium bromide (CTAB) in a series of 1,3-butanediol/water mixed solvent at room temperature was also investigated. From the conductivity measurements, the critical micelle concentration and the degree of counterion dissociation of CTAB were obtained as a function of 1,3-butanediol. Standard free energy of micellization, as a function of 1,3-butanediol contents, was also estimated and discussed. Gibbs energies of micellization were found to have a good correlation with dielectric constant and Gordon parameters.