Hydrogen dihexadecylphosphate

Rotational dynamics of a fluorescent dye adsorbed at the interface provides useful information concerning the rigidity of the microenvironment of liquid-liquid interface in terms of the interfacial viscosity. The rotational relaxation time of the rhodamine B dye was studied by the time-resolved total internal reflection fluorescent anisotropy. In-plane rotational relaxation time of octadecylrhodamine B cation was evaluated under the presence or absence of a surfactant [26]. Table 2.8 shows that by adding a surfactant, the relaxation time and the interfadal viscosity increased. Anionic surfactants SDS and HDHP (hydrogen dihexadecylphosphate) were more effective in reducing the rotational motion, because of the electrostatic interaction. HDHP with double long chains hindered the interfacial rotation more [40]. 

Tricot, Y.-M. and Fendler, J.H., Colloidal catalyst-coated semiconductors in surfactant vesicles In situ generation of Rh-coated CdS particles in dihexadecylphosphate vesicles and their utilization for photosensitized charge separation and hydrogen generation, /. Am. Chem. Soc., 106, 7359,1984. 

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