Rapid confocal imaging of vesicle-to-sponge phase droplet transition in dilute dispersions of the C(10)E(3) surfactant

The lamellar-to-sponge phase transition of fluorescently labelled large unilamellar vesicles (LUVs) of the non-ionic surfactant triethylene glycol mono n-decyl ether (C(10)E(3)) was investigated in situ by confocal laser scanning microscopy (CLSM). Stable dispersions of micrometer-sized C(10)E(3) LUVs were prepared at 20 °C and quickly heated at different temperatures close to the lamellar-to-sponge phase transition temperature. Phase transition of the strongly fluctuating individual vesicles into micrometre-sized sponge phase droplets was observed to occur via manyfold multilamellar morphologies with increasing membrane confinement through inter- and intra- lamellar fusion. The very low bending rigidity and lateral tension of the C(10)E(3) bilayer were supported by quantitative image analysis of a stable fluctuating membrane using both flicker noise spectroscopy and spatial autocorrelation function.