SMALL-ANGLE NEUTRON-SCATTERING (SANS) DETERMINATION OF THE VOLUME OCCUPIED BY A SINGLE WATER MOLECULE IN THE INVERTED MICELLAR SYSTEMS AOT+X(H,D)2O+C10D22 BY INTERNAL CONTRAST VARIATION TECHNIQUE

we performed the small-angle neutron scattering measurements on the AO T + X(H,D)2O + C10D22 reverse micellar solution over a wide range of w ater molar ratios X = 3 - 40. We determined the match - point b(c), th e aggregation numbers N, the radii of the spherical water nuclei rw , the area per head group of surfactant a0 and the volumes of single wat er molecules in micelles v(w). In detail we obtained v(w) = 143 angstr om3 for X = 3, v(w) = 53 angstrom3 for X = 7, v(w) = 45 angstrom3 for X = 14, v(w) = 31 angstrom3 for X = 20 and v(w) = 27 angstrom3 for X = 40. All these data show that with increasing water nucleus size the v olume per water molecule decreases and reaches the volume of the water molecule in bulk at X greater-than-or-equal-to 20.