title: Current-induced formation of gradient crystals in block copolymer electrolytes.
abstract: Conventional ordered phases such as crystals and liquid crystals have constant domain spacings. In this Letter, we report on the formation of coherently ordered morphologies wherein the domain spacing changes continuously along a specified direction. We have coined the term "gradient crystal" to refer to this structure, a signature of which is a small-angle X-ray scattering pattern that resembles a sundial. Gradient crystals composed of a gyroid morphology form spontaneously when ionic current is driven through a block copolymer electrolyte. We propose that this structure forms because it allows for a continuous change in domain spacing without requiring the introduction of defects. Previous studies have shown that applied electric fields ranging from 1000 to 40,000 V/mm can induce long-range structural order, alignment, and morphological transitions in block copolymers. Gradient crystals form under applied electric fields as low as 2.5 V/mm due to the presence of direct ionic currents that are absent in the aforementioned studies.
authors.affiliation: Department of Chemical Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Mullin
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Stone
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Teran
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Hallinan
authors.forename: A
authors.initials: A
authors.lastname: Hexemer
authors.forename: Nitash P
authors.initials: NP
authors.lastname: Balsara
mesh_terms: D003460:Crystallization / Q000379:methods*; D004563:Electrochemistry / Q000379:methods; D004573:Electrolytes / Q000737:chemistry* / Q000528:radiation effects*; D004574:Electromagnetic Fields; D046911:Macromolecular Substances / Q000737:chemistry / Q000528:radiation effects; D008422:Materials Testing; D008968:Molecular Conformation / Q000528:radiation effects; D049329:Nanostructures / Q000737:chemistry* / Q000528:radiation effects*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects*; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D004573:Electrolytes; D046911:Macromolecular Substances; D011108:Polymers