PHASE-DIAGRAM OF TYLOXAPOL AND WATER .2.

The phase diagram of mixtures of tyloxapol, a nonionic liquid polymer of the alkyl aryl polyether alcohol type, and water and the correspond ing liquid crystalline phases have been investigated by X-ray scatteri ng. Below 35 wt% tyloxapol micellar solutions are formed. At 3 wt% the y contain spherical micelles with a diameter around 7 nm. Increasing c oncentrations give rise to interparticle interactions that are clearly observable above 10 wt%. Complementary viscosity measurements indicat e a pronounced hydration of the polyoxyethylene chains. From 37.5 to 6 5 wt% there is a lyotropic liquid crystalline hexagonal phase (middle phase, M(1) phase). Its lattice parameter increases nearly linearly wi th water concentration but is almost independent of temperature. There are no transitions of the hexagonal phases to thermotropic liquid cry stalline phases at temperatures between 20 and 65 degrees C. At 65 deg rees C all systems exhibit two broad diffuse reflections with a spacin g ratio of 1:1/2. At all concentrations, samples heated to 65 degrees C and cooled to room temperature return to the hexagonal phase. The X- ray data confirm the existence of a cubic phase in a narrow concentrat ion. range around 70 wt% below 30 degrees C. Its three-dimensional str ucture, however, could not be determined from the eight reflections in the scattering pattern. Retransformation of the cubic phase from the melt is highly retarded. On cooling, the cubic phase which is closest to the hexagonal phase at 20 degrees C forms a metastable hexagonal in termediate phase with a small lattice parameter. The melts of cubic ph ases which exist in the vicinity of the lamellar phase region form an intermediate lamellar phase. Between 74 and 80 wt% at room temperature there is a liquid crystalline lamellar phase. The reflections of the thermally unstressed samples are weak compared with the sharp reflecti ons observed after cooling of molten samples. The melts of all three l iquid crystalline phases are viscous liquids. Their scattering pattern s display two broad maxima with spacings progressively decreasing from 5.3 to 4.6 nm and from 2.7 to 2.4 nm as the concentration increases f rom 37.5 to 77.5 wt%. No liquid crystalline phases were observed for t he binary mixtures containing more than 80 wt% but these highly viscou s liquids display a broad maximum around 4.2 nm.