Abstract: The Raman and FT-IR spectra of a 30% aqueous solution of cetyltrimethylammonium bromide have been investigated. A transition from coagel to micelle phase was observed at 300K. In the coagel phase, the hydrocarbon molecules exist in the bent end-methyl TG conformation with a few kink GTG′ forms. In the micellar phase, the number of GTG′ conformers increases, and the gauchetrans-ganche(GTG) and the doublegauche (GG) conformers exist in considerable concentrations.

Key words: cetyltrimethylammonium bromide, thermotropic.phase transition, molecular conformation, vibrational spectra