Pressure dependence of the chemical potential of tetradecyldimethylaminoxide micelles in D2O. A SANS study

By means of small-angle neutron scattering (SANS) experiments the dependenc e on pressure of the mean aggregation number [N] of rodlike tetradecyldimet hylaminoxide (TDMAO) micelles in D2O was determined for pressures up to 200 0 bar, at temperatures of 280.8, 294.9, and 308.1 K and at a TDMAO concentr ation c = 118 mM L-1. By an analysis via the so-called ladder model, the de pendence of the difference of the chemical potentials on pressure for a mon omer being located in the end cap and in the cylindrical part of the sphero cylindrical micelles, respectively, was extracted. This difference depends on concentration c, pressure P, and strongly on temperature T. For the two lower temperatures, pressure-induced phase transition was observed.