title: Mechanism of the transition between lamellar and gyroid phases formed by a diblock copolymer in aqueous solution.
abstract: The mechanism of the transition from a lamellar phase to a gyroid phase in an aqueous solution of a diblock copolymer has been studied by time-resolved synchrotron small-angle X-ray scattering. The transition occurs via a metastable perforated lamellar structure. The perforations initially have liquidlike ordering before developing hexagonal packing. The transient phase of irregularly perforated layers is revealed by the development of diffuse scattering peaks, just below the Bragg peaks of the lamellar structure. The diffuse scattering is modeled by Monte Carlo simulations of perforated layers. Following the formation of perforations, Bragg peaks characteristic of a hexagonal structure signal an ordering into a hexagonal lattice (with the concomitant loss of diffuse scattering). Computer simulations based on a dynamic density functional model reproduce these features. The hexagonal perforated lamellar phase is rapidly replaced by the gyroid phase. The domain spacing of the gyroid phase is larger than that of the perforated lamellar structure. The perforated lamellar and gyroid phases coexist for a defined period. The reverse transition from gyroid to lamellae occurs directly, with no transient or metastable intermediates.
authors.affiliation: Department of Chemistry, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Ian W
authors.initials: IW
authors.lastname: Hamley
authors.forename: Valeria
authors.initials: V
authors.lastname: Castelletto
authors.forename: Oleksandr O
authors.initials: OO
authors.lastname: Mykhaylyk
authors.forename: Zhuo
authors.initials: Z
authors.lastname: Yang
authors.forename: Roland P
authors.initials: RP
authors.lastname: May
authors.forename: Kateryna S
authors.initials: KS
authors.lastname: Lyakhova
authors.forename: G J Agur
authors.initials: GJ
authors.lastname: Sevink
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Zvelindovsky
mesh_terms: D003198:Computer Simulation; D000431:Ethanol / Q000031:analogs & derivatives / Q000737:chemistry; D005027:Ethylene Oxide / Q000737:chemistry; D008956:Models, Chemical; D009010:Monte Carlo Method; D044367:Phase Transition; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014965:X-Rays
chemical_list: C403469:2-(2-methoxyethoxy)ethanol; D011108:Polymers; D012996:Solutions; D014867:Water; D000431:Ethanol; D005027:Ethylene Oxide