Raman scattering and water structure in nonionic amphiphile solutions.
The structure of water in aqueous solutions of polyoxyethylene nonionic amphiphiles ${\mathrm{C}}_{10}$${\mathrm{E}}_{5}$, where ${\mathrm{E}}_{5}$ denotes ${\mathrm{H}}_{21}$(${\mathrm{OCH}}_{2}$${\mathrm{CH}}_{2}$${)}_{5}$OH, is studied by Raman scattering along an isothermal path crossing the isotropic one-phase region from 0 to 1 amphiphile volume fraction \ensuremath{\varphi}. The isotropic OH stretching-vibration spectrum points out a water behavior that depends on the amphiphile concentration. The data analysis is performed using the bond-percolation model developed for water. The interpretation of scattering data leads to the following structural picture for the water in the systems: for \ensuremath{\varphi} lower than 0.75, water is partially bound to the oxyethylene groups of the amphiphile; above \ensuremath{\varphi}=0.75 all water present in the system is bound. Analogously to the behavior of water in confined geometries, the structure of bound water presents a local fourfold-coordinated environment.
Small-angle neutron-scattering study of concentrated nonionic-amphiphile solutions
The structure of aqueous solutions of two polyoxyethylene non-ionic amphiphiles, C10E5 and C8E4, is studied by small-angle neutron-scattering along isothermal paths crossing the isotropic single-phase region from 0% to 100% amphiphile volume fractions. The scattered intensityI(k) shows a peak at a valuekm, which grows monotonically as the amphiphile volume fraction ϕ increases. The interpretation of the scattering data lead to the following conclusion: as Φ increases the micellar structure becomes less and less sharp, but some orientational correlations between neighboring amphiphile molecules are preserved even in the pure amphiphile phase.
Water self-diffusion in nonionic surfactant solutions. Hydration and obstruction effects
Determination par spectrometrie RMN, a echo de spin et a grandient de champ pulse, du coefficient d'autodiffusion de l'eau (D 2 O) dans des solutions aqueuses d'agents de surface non ioniques (ether de lauryle de pentaethyleneglycol ou d'octaethyleneglycol), de differentes concentrations et temperatures. On note que l'hydratation est de l'ordre de 4 a 6 molecules d'eau par groupe ethylene oxyde pour des solutions a 10% d'agent de surface