Mixed micelles of triton X-100 and cetyl trimethylammonium bromide in aqueous solution studied by H-1 NMR

NMR chemical shift, spin-lattice relaxation time, spin-spin relaxation time , and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurement s show that Triton X-100 (TX-100) molecules coaggregate with cetyl trimethy lammonium bromide (CTAB) molecules in aqueous solutions. The concentration of TX-100 in the mixed solutions of this study is 3 mM, with varying molar ratios of CTAB/TX-100 (C/T) ranging from 0.5 to 2.9. The results give infor mation about the structure of the mixed micelles. The cr-methylene group of CTAB is in the near vicinity of the phenoxy ring of TX-100; The trimethyl group attached to the polar head of CTAB locates between the first oxyethyl ene group next to the phenoxy ring of TX-100, and the end methyl group of C TAB is close to those of TX-100. The closely packed (coiled) hydrophilic po lyoxyethylene chains in the exterior part of the mixed micelles gradually e xtend with an increase in CIT in the mixed solution. CTAB and TX-100 molecu les are uniformly mixed in the micelles in each mixed solution.