Formation of micellar nematic phases from surfactants and aqueous orthophosphoric acid

Abstract

Abstract It is shown that aqueous orthophosphoric acid can be used as a solvent for cationic surfactants to form micellar nematics which align spontaneously in magnetic fields. The cationic surfactants investigated were decylammonium chloride (DAC1) and decylammonium dihydrogen phosphate (DAPH2). The percentage of pure H3PO4 in the nematic phases of DAC1 could be varied from 10 to 70 per cent while DAPH2 gave a nematic phase in a narrow range with 60 per cent H3PO4. As the percentage of pure H3PO4 in the DAC1 nematic phase increased, the 23Na quadrupolar splitting decreased; this was attributed to an alteration in the binding sites of these systems. 31P N.M.R. of H3PO4 in DAC1 and DAPH2 nematic phases gave a symmetric singlet indicating that the chemical shift of H3PO4 in these systems is isotropic. A mixture of the anionic surfactants, sodium decylsulphate (SDS) with 10 per cent H3PO4 gave a micellar nematic phase as a result of a replacement reaction in which orthophosphoric acid monodecylester (PDE) wa...