CHARACTERIZATION OF THE NANOSTRUCTURES IN LIQUID-CRYSTALLINE MESOPHASES PRESENT IN THE TERNARY-SYSTEM BRIJ-35 DIBUTYL ETHER H2O BY SMALL-ANGLE AND WIDE-ANGLE X-RAY-SCATTERING

We investigated the liquid crystalline phase structures and their temp erature-dependent dynamics in the ternary system composed of Brij-35 [ poly(oxyethylene(similar to 23))lauryl ether, C12OEsimilar to 23], dib utyl ether (DBE) and 10 mM Na/K buffer. A sequence of schematic ternar y phase diagrams at 10, 20, 30, 40, and 60 degrees C, derived from tem perature-scanning small- and wide-angle X-ray scattering (SWAX), has b een established. In the binary Brij-35/H2O system, the amphiphilic com ponent Brij-35, being totally miscible with water, self-assembles as a function of its concentration into a normal micellar solution L-1, a normal packed micellar cubic I-1-phase region, and an extended region of various lamellar structures. The cubic I-1 phases show diffraction patterns with Im3m (unit cell parameter a(Im3m) = 85-94 Angstrom) and Ia3d (a(Ia3d) = 162-167 Angstrom) symmetry. Increasing temperature des tabilizes the cubic phases between 15 and 55 degrees C, depending on t he weight ratio of the used components. The lamellar phases show unit cell dimensions of a = 179-181 Angstrom. A phase transition from L-c ( crystalline lamellar phase), L-beta (gel lamellar phase), to a isotrop ic micellar phase, here denoted as L-2, occurs at temperatures from 15 to 35 degrees C, as a function of the water content. The DBE uptake o f these structures is limited to 20-50%(w/w), which generates biphasic regions at higher DBE amounts, where a DBE excess phase containing ap proximately 2% (w/w) H2O and 0.02% (w/w) Brij-35 is formed. Increasing amounts of DBE lead-with exception of the L-c phase-to enhanced phase temperature stabilities in the water-lean region and induce normal he xagonal H-1 (a = 68-135 Pi) and various cubic structures. We found the cubic space groups Im3m and Ia3d with unit cell dimensions a(Im3m) = 83-112 Angstrom and a(Ia3d) = 162-195 Angstrom in the cubic Il region and Pn3m (a(pn3m) = 164 Angstrom) and Ia3d (a(Ia3d) = 187-214 Angstrom ) as well as Fd3m (a(Fd3m) = 218-275 Angstrom) in the cubic region wit h low water contents.