Phase behavior of tyloxapol/Triton X100/water mixtures

The influence of admixture of Triton X100 to the polymer tyloxapol and the phase behavior of the mixtures in contact with water was investigated by viscometry, polarization microscopy, and X-ray scattering. The viscosity of tyloxapol/Triton X100 mixtures is lower than that of pure tyloxapol. With increasing Triton X100 content, the phase behavior of the surfactant mixtures in contact with water evolves from the complex behavior of tyloxapol to the simpler one of Triton X100. In contact with water, mixtures rich in tyloxapol form hexagonal, cubic, and lamellar lyotropic liquid crystalline phases over a wide range of concentration and temperature, whereas Triton X100/water mixtures form only a hexagonal phase in a limited concentration and temperature range. The polymeric nature of tyloxapol stabilizes the liquid crystalline structures, and the size of the supramolecular structures in the water-containing surfactant systems is independent of the tyloxapol/Triton X100 mixing ratio but depends highly on water content. The ability of tyloxapol to form stable lyotropic liquid crystalline phases at body temperature, which has been proposed as a basis for the development of novel peroral sustained-release systems, is not significantly impaired by the addition of appropriate amounts of Triton X100. Admixture of Triton X100 to tyloxapol may thus provide a way to circumvent processing problems during the preparation of pharmaceutical formulations based on the highly viscous tyloxapol.