Mixed Micelles of Triton X-100 and Cetyl Trimethylammonium Bromide in Aqueous Solution Studied by 1H NMR

Abstract

1H NMR chemical shift, spin−lattice relaxation time, spin−spin relaxation time, and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurements show that Triton X-100 (TX-100) molecules coaggregate with cetyl trimethylammonium 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 information about the structure of the mixed micelles. The α-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 oxyethylene group next to the phenoxy ring of TX-100, and the end methyl group of CTAB is close to those of TX-100. The closely packed (coiled) hydrophilic polyoxyethylene chains in the exterior part of the mixed micelles gradually extend with an increase in C/T in the mixed solution. CTAB and TX-100 molecules are uniformly mixed in the micelles in ...