title: Fast diffusion-limited lyotropic phase transitions studied in situ using continuous flow microfluidics/microfocus-SAXS.
abstract: Fast concentration-induced diffusion-limited lyotropic phase transitions can be studied in situ with millisecond time resolution using continuous flow microfluidics in combination with microfocus small-angle X-ray scattering. The method was applied to follow a classical self-assembly sequence where amphiphiles assemble into micelles, which subsequently assemble into an ordered lattice via a disorder/order transition. As a model system we selected the self-assembly of an amphiphilic block copolymer induced by the addition of a nonsolvent. Using microchannel hydrodynamic flow-focusing, large concentration gradients can be generated, leading to a deep quench from the miscible to the microphase-separated state. Within milliseconds the block copolymers assembly via a spinodal microphase separation into micelles, followed by a disorder/order transition into an FCC liquid-crystalline phase with late-stage domain growth and shear-induced domain orientation into a mesocrystal. A comparison with a slow macroscopic near-equilibrium kinetic experiment shows that the fast structural transitions follow a direct pathway to the equilibrium structure without the trapping of metastable states.
authors.affiliation: Physical Chemistry I and ‡Macromolecular Chemistry I, University of Bayreuth , Universitätsstr. 30, 95447 Bayreuth, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: With
authors.forename: Martin
authors.initials: M
authors.lastname: Trebbin
authors.forename: Christian B A
authors.initials: CB
authors.lastname: Bartz
authors.forename: Christian
authors.initials: C
authors.lastname: Neuber
authors.forename: Martin
authors.initials: M
authors.lastname: Dulle
authors.forename: Shun
authors.initials: S
authors.lastname: Yu
authors.forename: Stephan V
authors.initials: SV
authors.lastname: Roth
authors.forename: Hans-Werner
authors.initials: HW
authors.lastname: Schmidt
authors.forename: Stephan
authors.initials: S
authors.lastname: Förster