J. Phys. II France
Volume 3, Numéro 4, April 1993
Page(s) 515 - 530
DOI: 10.1051/jp2:1993148
J. Phys. II France 3 (1993) 515-530

Transient behavior and relaxations of the L 3 (sponge) phase : T-jumb experiments

G. Waton1 and G. Porte2

1  Laboratoire d'Ultrasons et de Dynamique des Fluides Complexes associé au CNRS, Université Louis Pasteur, 4 rue Blaise Pascal, 67070 Strasbourg Cedex, France
2  Groupe de Dynamique des Phases Condensées associé au CNRS, Université Montpellier II, Case 026, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France

(Received 26 October 1992, accepted 29 December 1992)

We report here on a systematic time resolved investigation of the transient behavior of the sponge phase after an abrupt temperature jump. We obtain evidence for three distinct relaxation times $\tau_{1}, \tau_{2}$ and $\tau_{3}$ having very different magnitudes. We show that $\tau_{1}$ is related to a conserved internal variable while $\tau_{2}$ and $\tau_{3}$ both correspond to the relaxations of unconserved thermodynamic variables. We propose an interpretation of the transient behavior based on the idea that the temperature jump essentially puts the membrane in L 3 under transient tension. According to this interpretation, $\tau_{1}$ corresponds to the relaxation of concentration fluctuations, $\tau_{2}$ to that of the degree of symmetry of the structure and $\tau_{3}$ to that of its density of connectivity. This picture actually accounts at least qualitatively for the experimental observation. Moreover, the temperature dependences of $\tau_{2}$ and $\tau_{3}$ close to the sponge-to-lamellar transition temperature indicate that this transition is quite weakly first order.

42.20J - 82.70D - 66.10C - 61.25

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