PROPERTIES OF A DICHAINED SUGAR SURFACTANT

We have studied the properties of a novel nonionic surfactant possessing two Cg hydrophobic chains and two nonionic glucamide head groups (C6H13)(2)C(CH2NHCO(CHOH)(4)CH2OH)(2), i.e. 7,7-bis[(1,2,3,4,5-pentahydroxyhexanamido)methyl]-n-tridecane or di-(C6-Glu). The changes in air-water surface tension gamma with concentration show a critical micelle concentration (cmc) at 1.9 x 10(-3) mol dm(-3). A value for a(s), the mean area per molecule in the pre-cmc monolayer, of 75 +/- 3 Angstrom(2) was obtained using the Gibbs adsorption isotherm. The binary di-(C6-Glu)-water phase diagram has been determined using polarizing optical microscopy and H-2 NMR. At 27 degrees C the phase progression hydrated crystals S --> lamellar L(alpha) --> cubic V-1 --> hexagonal H-1 --> micellar solution L(1) occurs with decreasing surfactant concentration. In contrast to many polyether nonionics (C(i)E(j)) this surfactant does not exhibit cloud-point phase separation between 0 and 100 degrees C. Analysis of small-angle neutron scattering data at concentrations 43, 20, and 8 x cmc indicates the presence of cylindrical micelles, 140-200 Angstrom long and radius similar to 12 Angstrom. The micelle shape and size are not significantly affected by temperature up to 70 degrees C.