TRANSIENT-BEHAVIOR AND RELAXATIONS OF THE L3 (SPONGE) PHASE - T-JUMP EXPERIMENTS

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 tau1, tau2 and tau3 having very different magnitudes. We show that tau1 is related to a conserved internal variable while tau2 and tau3 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 L3 under transient tension. According to this interpretation, tau1 corresponds to the relaxation of concentration fluctuations, tau2 to that of the degree of symmetry of the structure and tau3 to that of its density of connectivity. This picture actually accounts at least qualitatively for the experimental observation. Moreover, the temperature dependences of tau2 and tau3 close to the sponge-to-lamellar transition temperature indicate that this transition is quite weakly first order.