6533b830fe1ef96bd1296fa0

RESEARCH PRODUCT

Latent Heat of Spontaneous-Curvature-Induced Lamellar-to-Microemulsion Transitions

subject

description

Using differential scanning microcalorimetry we examine the latent heat of the temperature-induced structural transition from a lamellar to a microemulsion phase in a H2O/n-octane/C12E5 (n-dodecyl pentanethyleneglycol ether) system. The associated latent heat increases strongly with surfactant concentration yielding heat changes up to 1kB T per surfactant molecule. These large values are quantitatively described by an interfacial model which takes into account the temperature dependence of the spontaneous curvature. The model explains our data points without considering contributions to the free energy by thermal fluctuations, entropy of mixing, undulations of the lamellae and renormalization of the bending constants. Apparently they are of minor importance to describe this transition.