EFFECT OF ORGANIC ADDITIVES OR COUNTERIONS ON THE SUPRAMOLECULAR ASSEMBLY STRUCTURES CONSTRUCTED BY AMPHIPHILES - A SMALL-ANGLE NEUTRON-SCATTERING INVESTIGATION

Small-angle neutron scattering (SANS) was measured for aqueous solutio ns of amphiphiles with organic additives or counterions such as 2-inde necarboxylic acid, cinnamic acid, and salicylic acid or their ions. Th e effect of organic species on the supramolecular assembly structure w as investigated. Equimolar mixtures of dodecyldimethylamine oxides and aromatic carboxylic acids constructed vesicles. The vesicular bilayer thicknesses were 29-30 Angstrom, independent of organic species. On t he other hand, hexadecyltrimethylammoniums with aromatic carboxylate c ounterions always formed rodlike micelles with axial ratios 8-10. Aque ous solutions of tetradecyltrimethylammonium salicylate displayed a st rong interparticle interference effect on SANS profiles at concentrati ons above 0.8 x 10(-2) g cm(-3), although such an effect disappeared w ith addition of more than 5/mM sodium salicylate.