title: Thermo-cross-linked elastomeric opal films.
abstract: An efficient and convenient thermal cross-linking protocol in elastomeric opal films leading to fully reversible and stretch-tunable optical materials is reported. In this study, functional monodisperse core-shell particles were arranged in a face-centered cubic (fcc) lattice structure by a melt flow process. A problem up to now was that un-cross-linked films could not be drawn fully reversibly and hence lost their optical and mechanical performance. After thermal cross-linking reaction, the obtained films can be drawn like rubbers and the color of their Bragg reflection changes because of controlled lattice deformation, which makes the cross-linked films mechanochromic sensors. Different techniques were developed for the cross-linking of the films a posteriori, after their preparation in the melt flow process. A photo-cross-linking approach was reported earlier. This study now deals with a very efficient thermo-cross-linking approach based on the chemistry of hydroxyl- and isocyanate-functionalities that form urethane bridges. The focus of the present work is the mechanism and efficiency of this cross-linking process for elastomeric opal films with excellent mechanical and optical properties.
authors.affiliation: Ernst-Berl Institut für Technische und Makromolekulare Chemie, Technische Universität Darmstadt , Alarich-Weiss-Straße 4, D-64287 Darmstadt, Germany.
authors.forename: Christian G
authors.initials: CG
authors.lastname: Schäfer
authors.forename: Benjamin
authors.initials: B
authors.lastname: Viel
authors.forename: Goetz P
authors.initials: GP
authors.lastname: Hellmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Rehahn
authors.forename: Markus
authors.initials: M
authors.lastname: Gallei