A FOURIER-TRANSFORM IR STUDY OF THE PHASE-TRANSITIONS AND MOLECULAR ORDER IN THE HEXADECYLTRIMETHYLAMMONIUM SULFATE WATER SYSTEM/

Variable temperature Fourier transform infrared (FTIR) spectroscopy wa s used to study the transition between the micellar and the coagel pha ses, and between the cubic and the coagel phases, for the hexadecyltri methylammonium sulfate (CTAS)/water system. The phase transition takes place at 15 degrees C for the coagel to micelle transition and 17 deg rees C for the coagel to cubic phase transition. CTAS in the solid sta te at two temperatures was also studied by FTIR to provide comparison with the aqueous samples on the molecular motion and packing in these phases. The present FTIR data also suggest the formation of rod-like m icelles upon the addition of electrolyte, NaCl, to the CTAS/water syst em. (C) 1997 Academic Press.