The scale factor does not increase drastically with increasing concentration, showing that the addition of more 2NapFF molecules to the system does not simply result in more cylinders in solution, but rather adds length to the existing cylinders and promotes micellar branching. As the concentration increases from the dilute to what might be considered the semi-dilute regime in both samples, a peak (Q*) appears at low Q. This peak represents the correlation length of the system, ξ, sometimes called the screening length, and is the scale at which for charged systems all charge repulsions are screened. De Gennes showed for polyelectrolytes that the concentration dependence of a correlation length in solution can be rationalized simply by a scaling argument, and that for a fully extended polyelectrolyte in the absence of salt, ξ ~c1/2 . Polyelectrolytes in the absence of salt will show a peak at Q = 2πξ -1 ; the peak is due to large osmotic pressures in polyelectrolyte solutions which do not allow correlation volumes to overlap as they might, for example, in a good solvent. A log-log plot of ξ against concentration for 2NapFF-Na has a gradient of c 0.46 , close to the value expected by the scaling law for a polyelectrolyte with no salt (Figure ). Therefore, each wormlike micelle can be considered as a polyelectrolyte chain. At pH 10.5, each wormlike micelle is negatively charged.