Effect of mixing on the morphology of cylindrical micelles.
Increasing the spontaneous curvature of an amphiphile can lead to a first-order morphology transition from threadlike micelles to a branched network. The two morphologies were linked to entropy-driven topological defects; networks are dominated by Y-junctions, while linear threadlike structures are dominated by spherical end-caps. In this paper we investigate the effect of mixing on the morphological transitions in nonionic amphiphilic systems. We find that mixed equilibrium structures are obtained within seconds; these mixed cylindrical structures display comparable numbers of end-caps and branch points, resulting in a novel 'short armed' branched (SAB) morphology. Quite surprisingly, the probability of either defect (end-caps or branch points) is independent of composition, so that neither a first-order nor a second-order morphological transition is observed. A possible explanation may be local demixing of the two amphiphilic components, which adds a degree of freedom and thus enables the formation of a unique morphology that cannot be obtained in single-component systems. We further find that within a relatively large composition range phase equilibrium exists between vesicles, SAB micelles, and spherical micelles.
Dan
Nily
N
Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, USA. dan@coe.drexel.edu
Shimoni
Karin
K
Pata
Veena
V
Danino
Dganit
D
D002070:Butadienes / Q000737:chemistry; D020285:Cryoelectron Microscopy; D019277:Entropy; D007700:Kinetics; D008027:Light; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D020959:Polyethylene / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D012542:Scattering, Radiation; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature
D002070:Butadienes; D008823:Micelles; D011108:Polymers; D013501:Surface-Active Agents; C473741:poly(1,2-butadiene-b-ethylene oxide); D020959:Polyethylene