Sol-gel transition in worm-like micelles |
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Authors: | F Aliotta M E Fontanella C Vasi M Sacchi G La Manna V Turco-Liveri |
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Institution: | (1) Istituto di Tecniche Spettroscopiche del CNR, Messina, Italy;(2) Dipartimento di Fisica dell’Università, Messina, Italy;(3) Dipartimento di Chimica Fisica dell’Università, Palermo, Italy |
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Abstract: | Summary The statical and dynamical properties of lecithin/H2O/cyclohexane cylindrical reverse micelles are investigated as a function of lecithin volume fraction, ϕ, and temperature
at fixed water/lecithin ratio,w
0. The viscosity data are well fitted by the Cates model when the breathing mode of micelles is taken into consideration, overlapping
with the breaking and reforming mechanisms. We present some results from Brillouin-scattering experiment, performed across
the sol-gel transition. In order to explain the experimentally observed ϕ-dependence of the hyperacoustic parameters, a mechanical
model was developed from which the ϕ-dependence of the micelle size distribution was obtained. From a comparison with the
viscosity data the entanglement length was estimated. Furthermore some new results from an incoherent quasi-elastic neutron
scattering experiment are presented. The whole body of the experimental results suggests for a sol-gel transition triggered
by topologic phenomena. When the lecithin volume fraction increases, the kinetic equilibrium between the breaking and reforming
mechanisms of the micelles shifts the mean micelle length towards higher values and the entanglement of the micelles becomes
highly favourable. The obtained results are discussed and compared with other findings in literature.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. |
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Keywords: | Neutron scattering techniques (including small-angle scattering) |
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