Structure of the polar head layer and water penetration in a cationic micelle

Contrast variation neutron small angle scattering experiments have been used to determine the configuration of the polar head groups in cationic micelles of tetradecyl trimethyl ammonium bromide in which either the paraffin chain or trimethyl ammonium polar head had been selectively deuterated. The polar heads form a compact shell at the exterior of the micelle having a mean thickness of 2·0±0·1 Å. There is almost no water penetration in this layer nor in the paraffin core. The surface of the micelle is relatively smooth there being few head groups more than one methylene group away from the surface.