title: Finger-like pattern formation in dilute surfactant pentaethylene glycol monododecyl ether solutions.
abstract: We report here peculiar finger-like patterns observed during the phase separation process of dilute micellar pentaethylene glycol monododecyl ether solutions. The patterns were composed of parallel and periodic threads of micelle-rich domains. Prior to this pattern formation, the phase separation always started with the appearance of water-rich domains rimmed by the micelle-rich domains. It was found that these rims played a significant role in the pattern formation. We explain this pattern formation using a simple simulation model with disconnectable springs. The simulation results suggested that the spatially inhomogeneous elasticity or connectivity of a transient gel of worm-like micelles was responsible for the rim formation. The rims thus formed lead rim-induced nucleation, growth, and elongation of the domains owing to their small mobility and the elastic frustration around them. These rim-induced processes eventually produce the observed finger-like patterns.
authors.affiliation: Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima 739-8521, Japan.
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Kubo
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yokoyama
authors.forename: Shinpei
authors.initials: S
authors.lastname: Tanaka