A DOUBLY BRANCHED NONIONIC OLIGOOXYETHYLENE V-AMPHIPHILE - EFFECT OF MOLECULAR-GEOMETRY ON LIQUID-CRYSTALLINE PHASE-BEHAVIOR .3.

The synthesis of a double-chain nonionic surfactant, 1,3-bis-(2-ethylhexyloxy)-2-propoxy-octaoxyethylene monomethyl ether, with a doubly branched lipophilic moiety is described. The lyotropic phase behavior of this surfactant with water is investigated by polarizing microscopy, and X-ray diffraction and deuterium NMR spectroscopy on D2O-enriched surfactant/water mixtures. A broad liquid-crystalline regime is found, which consists of two regions of different lamellar structure. Compared to other aqueous oligooxyethylene surfactants of the same hydrophilic-lipophilic balance but different molecular architecture, the phase diagram of the doubly branched amphiphile/water system shows a stabilization of the lamellar phase, confirming the strong influence of molecular geometry on lyotropic phase behavior. © 1994 by Academic Press, Inc.