Cooperative interaction between DDA and Brij 35. In order to further interrogate the physical chemistry of the extended H-Bond formation, we investigated what happens when a nonionic surfatant is mixed with an anionic surfactant. The data summarized in Figure and) show that the dodecanoic acid exhibits a red shift in water when mixed with Brij 35 even when the latter is present at a rather low concentration (2 ppm), which is evident in two related but separate experiments. In the experiment, Bij-35 pre-existed in the aqueous phase at a concentration of 50 ppm, DDA was then added starting with a concentration of 2 ppm and ending to about 50 ppm.