title: Influence of Backbone Fluorination in Regioregular Poly(3-alkyl-4-fluoro)thiophenes.
abstract: We report two strategies toward the synthesis of 3-alkyl-4-fluorothiophenes containing straight (hexyl and octyl) and branched (2-ethylhexyl) alkyl groups. We demonstrate that treatment of the dibrominated monomer with 1 equiv of alkyl Grignard reagent leads to the formation of a single regioisomer as a result of the pronounced directing effect of the fluorine group. Polymerization of the resulting species affords highly regioregular poly(3-alkyl-4-fluoro)thiophenes. Comparison of their properties to those of the analogous non-fluorinated polymers shows that backbone fluorination leads to an increase in the polymer ionization potential without a significant change in optical band gap. Fluorination also results in an enhanced tendency to aggregate in solution, which is ascribed to a more co-planar backbone on the basis of Raman and DFT calculations. Average charge carrier mobilities in field-effect transistors are found to increase by up to a factor of 5 for the fluorinated polymers.
authors.affiliation: †Department of Chemistry and Centre for Plastic Electronics, Imperial College London, Exhibition Rd, London SW7 2AZ, U.K.
authors.forename: Zhuping
authors.initials: Z
authors.lastname: Fei
authors.affiliation: †Department of Chemistry and Centre for Plastic Electronics, Imperial College London, Exhibition Rd, London SW7 2AZ, U.K.
authors.forename: Pierre
authors.initials: P
authors.lastname: Boufflet
authors.affiliation: ‡Department of Physics and Centre for Plastic Electronics, Imperial College London, Exhibition Rd, London SW7 2AZ, U.K.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Wood
authors.affiliation: ‡Department of Physics and Centre for Plastic Electronics, Imperial College London, Exhibition Rd, London SW7 2AZ, U.K.
authors.forename: Jessica
authors.initials: J
authors.lastname: Wade
authors.affiliation: §Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, U.K.
authors.forename: John
authors.initials: J
authors.lastname: Moriarty
authors.affiliation: ∥Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia.|⊥Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168, Australia.
authors.forename: Eliot
authors.initials: E
authors.lastname: Gann
authors.affiliation: #Department of Materials Science and Engineering, University of Arizona, Tucson, Arizona 85721, United States.
authors.forename: Erin L
authors.initials: EL
authors.lastname: Ratcliff
authors.affiliation: ∥Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: McNeill
authors.affiliation: §Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, U.K.
authors.forename: Henning
authors.initials: H
authors.lastname: Sirringhaus
authors.affiliation: ‡Department of Physics and Centre for Plastic Electronics, Imperial College London, Exhibition Rd, London SW7 2AZ, U.K.
authors.forename: Ji-Seon
authors.initials: JS
authors.lastname: Kim
authors.affiliation: †Department of Chemistry and Centre for Plastic Electronics, Imperial College London, Exhibition Rd, London SW7 2AZ, U.K.
authors.forename: Martin
authors.initials: M
authors.lastname: Heeney