title: Light-controlled supramolecular helicity of a liquid crystalline phase using a helical polymer functionalized with a single chiroptical molecular switch.
abstract: Control over the preferred helical sense of a poly(n-hexyl isocyanate) (PHIC) by using a single light-driven molecular motor, covalently attached at the polymer's terminus, has been accomplished in solution via a combination of photochemical and thermal isomerizations. Here, we report that after redesigning the photochromic unit to a chiroptical molecular switch, of which the two states are thermally stable but photochemically bistable, the chiral induction to the polymer's backbone is significantly improved and the handedness of the helical polymer is addressable by irradiation with two different wavelengths of light. Moreover, we show that the chiral information is transmitted, via the macromolecular level of the polyisocyanate, to the supramolecular level of a lyotropic cholesteric liquid crystalline phase consisting of these stiff, rodlike polymers. This allows the magnitude and sign of the supramolecular helical pitch of the liquid crystal film to be fully controlled by light.
authors.affiliation: Department of Organic and Molecular Inorganic Chemistry, Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
authors.forename: Dirk
authors.initials: D
authors.lastname: Pijper
authors.forename: Mahthild G M
authors.initials: MG
authors.lastname: Jongejan
authors.forename: Auke
authors.initials: A
authors.lastname: Meetsma
authors.forename: Ben L
authors.initials: BL
authors.lastname: Feringa
mesh_terms: D003460:Crystallization; D046911:Macromolecular Substances / Q000737:chemistry / Q000528:radiation effects*; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry / Q000528:radiation effects*; D010777:Photochemistry; D012996:Solutions / Q000737:chemistry / Q000528:radiation effects; D013237:Stereoisomerism; D013696:Temperature; D014050:Toluene / Q000737:chemistry / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D046911:Macromolecular Substances; D009570:Nitriles; D012996:Solutions; C514553:poly(n-hexyl isocyanate); D014050:Toluene