title: Efficient Light-Induced Phase Transitions in Halogen-Bonded Liquid Crystals.
abstract: Here, we present a new family of light-responsive, fluorinated supramolecular liquid crystals (LCs) showing efficient and reversible light-induced LC-to-isotropic phase transitions. Our materials design is based on fluorinated azobenzenes, where the fluorination serves to strengthen the noncovalent interaction with bond-accepting stilbazole molecules, and increase the lifetime of thecis-form of the azobenzene units. The halogen-bonded LCs were characterized by means of X-ray diffraction, hot-stage polarized optical microscopy, and differential scanning calorimetry. Simultaneous analysis of light-induced changes in birefringence, absorption, and optical scattering allowed us to estimate that <4% of the mesogenic units in thecis-form suffices to trigger the full LC-to-isotropic phase transition. We also report a light-induced and reversible crystal-to-isotropic phase transition, which has not been previously observed in supramolecular complexes. In addition to fundamental understanding of light-responsive supramolecular complexes, we foresee this study to be important in the development of bistable photonic devices and supramolecular actuators.
authors.affiliation: Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials, and Chemical Engineering "Giulio Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy.
authors.forename: Francisco
authors.initials: F
authors.lastname: Fernandez-Palacio
authors.affiliation: HYBER Centre of Excellence, Department of Applied Physics, Aalto University , P.O. Box 15100, FI-02150, Espoo, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Poutanen
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Marco
authors.initials: M
authors.lastname: Saccone
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Siiskonen
authors.affiliation: Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials, and Chemical Engineering "Giulio Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Terraneo
authors.affiliation: Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials, and Chemical Engineering "Giulio Natta", Politecnico di Milano , Via L. Mancinelli 7, 20131 Milano, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Resnati
authors.affiliation: HYBER Centre of Excellence, Department of Applied Physics, Aalto University , P.O. Box 15100, FI-02150, Espoo, Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Ikkala
authors.affiliation: Laboratory of Nanostructured Fluorinated Materials (NFMLab), Department of Chemistry, Materials, and Chemical Engineering "Giulio Natta", Politecnico di Milano, Via L. Mancinelli 7, 20131 Milano, Italy; HYBER Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 15100, FI-02150, Espoo, Finland; VTT-Technical Research Centre of Finland, Biologinkuja 7, 02150 Espoo, Finland.
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Metrangolo
authors.affiliation: Department of Chemistry and Bioengineering, Tampere University of Technology , P.O. Box 541, FI-33101 Tampere, Finland.
authors.forename: Arri
authors.initials: A
authors.lastname: Priimagi