Hydrotrope and hydrotrope-solubilization action ofof Vitamin C

Vitamin C (VC) is found to show the hydrotrope action when the aqueous solubility of surfactant is enhanced while it will show the hydrotrope-solubilization action when the solubility amount of oil in O/W microemulsion and that of water in W/O microemulsion are increased. Both the hydrotrope action and the hydrotrope-solubilization action of VC are selective so that they can only be found in cationic surfactant hexadecyltrimethylammonium bromide (CTAB) system. The addition of VC in CTAB system with n-C5H11OH as co-surfactant enlarges the O/W and W/O areas in the phase diagram and expands the bicontinuous region by reducing the lamellar liquid crystal area. The results show that the hydrotrope-solubilization action of VC is in fact a structural transition from the lamellar liquid crystal phase to the bicontinuous structure.