title: Self-assembled polymeric solid films with temperature-induced large and reversible photonic-bandgap switching.
abstract: In aqueous solutions the response of polymers and biological matter to external conditions, such as temperature and pH, is typically based on the hydrophobic/hydrophilic balance and its effects on the polymer conformation. In the solid state, related concepts using competing interactions could allow novel functions. In this work we demonstrate that polymeric self-assembly, reversibility of hydrogen bonding, and polymer-additive phase behaviour allow temperature response in the solid state with large and reversible switching of an optical bandgap. A complex of polystyrene-block-poly(4-vinylpyridinium methanesulphonate) and 3-n-pentadecylphenol leads to the supramolecular comb-shaped architecture with a particularly long lamellar period. The sample is green at room temperature, as an incomplete photonic bandgap due to a dielectric reflector is formed. On heating, hydrogen bonds are broken and 3-n-pentadecylphenol additionally becomes soluble in polystyrene, leading to a sharp and reversible transition at approximately 125 degrees C to uncoloured material due to collapse of the long period. This encourages further developments, for example, for functional coatings or sensors in the solid state.
authors.affiliation: Department of Engineering Physics and Mathematics and Center for New Materials, Helsinki University of Technology, PO Box 2200, FIN-02015 HUT, Espoo, Finland.
authors.forename: Sami
authors.initials: S
authors.lastname: Valkama
authors.forename: Harri
authors.initials: H
authors.lastname: Kosonen
authors.forename: Janne
authors.initials: J
authors.lastname: Ruokolainen
authors.forename: Tomi
authors.initials: T
authors.lastname: Haatainen
authors.forename: Mika
authors.initials: M
authors.lastname: Torkkeli
authors.forename: Ritva
authors.initials: R
authors.lastname: Serimaa
authors.forename: Gerrit
authors.initials: G
authors.lastname: Ten Brinke
authors.forename: Olli
authors.initials: O
authors.lastname: Ikkala
mesh_terms: D003460:Crystallization / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008027:Light; D008420:Manufactured Materials; D008422:Materials Testing; D008567:Membranes, Artificial; D055095:Optics and Photonics / Q000295:instrumentation*; D010777:Photochemistry / Q000295:instrumentation* / Q000379:methods; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects; D013696:Temperature
chemical_list: D008567:Membranes, Artificial; D011108:Polymers