Temperature and concentration effects on decyltrimethylammonium micelles in water

Wide-angle neutron scattering experiments combined with Empirical Potential Structural Refinement modelling have been used to study the detailed structure of decyltrimethylammonium bromide (C ₁₀TAB) micelles at two different temperatures; 25°C and 50°C and two concentrations; 0.4 and 0.8 M in water. At higher temperature, the micelles become smaller, and fewer counterions bind to the micelle surfaces, however, the headgroup positions are more ordered, possibly due to crowding in the smaller micelles. At higher concentration, the models suggest the micelles become elongated, although the aggregations numbers are smaller than those at the lower concentration. The smaller micelles found in 0.8 M solutions have more hydrated headgroups and lower counterion binding than the ellipsoidal micelles found in 0.4 M C ₁₀TAB solutions.