DYNAMIC LIGHT-SCATTERING FROM A HIGHLY SWOLLEN NONIONIC LAMELLAR LIQUID-CRYSTAL

We have conducted a dynamic light-scattering study of the homeotropica lly aligned highly swollen lamellar phase (layer separation d approxim ately 180 nm) of a nonionic binary system, dodecylpentaglycol (C12E5) and water, where the steric and entropic repulsion is the dominant int ermembrane force stabilizing the lamellar order. We have identified a hydrodynamic mode in the two momentum-transfer limits available to lig ht scattering. Based on previous models, we have found an explicit exp ression for the dispersion relation of this ''baroclinic'' or ''slip'' mode for systems with large layer spacing, which successfully explain s our experimental results. Where d is large, the bilayer curvature el asticity and the viscous coupling between water and the bilayers becom e more important to the understanding of the baroclinic mode. We found the curvature elastic constant k(c) congruent-to k(B)T, consistent wi th generally accepted values for flexible membranes.