The Effect of Salt on a Binary Lyotropic Liquid Crystal System

This study is conducted with the purpose of understanding the effect of inorganic salt (sodium bromide, NaBr) on the phase states, phase behaviour and physical properties of a binary lyotropic liquid crystal system (tetradecyl trimethyl ammonium bromide, TTAB + water). For this purpose, first the phase behaviour, lyotropic and thermotropic phase transitions, of the binary system was investigated and the phase diagram of the binary system was constructed. The refractive index and electrical conductivity values of all the mesophases defined in the binary system were determined in large temperature intervals. The refractive index – temperature, refractive index – concentration, electroconductivity – temperature and electroconductivity – concentration dependences were graphed analysed and presented. Later, we prepared a solution of ultrapure water and sodium bromide, with 95𝑤�����𝑡�����% water and 5𝑤�����𝑡�����% NaBr, and used it as solvent, instead of ultrapure water used in binary system, to prepare the samples. We repeated the procedure for the binary system, constructed a phase diagram and investigated the behaviour of physical parameters for this new system. To understand the effect of salt on the phase behaviour, lyotropic and thermotropic phase transitions and the polymorphism of the binary system the two-phase diagrams were compared, and the results were discussed. Likewise, to understand the effect on physical parameters all the dependences obtained and represented were compared and discussed.