Influence of Backbone Fluorination in Regioregular Poly(3-alkyl-4-fluoro)thiophenes

Zhuping Fei, Pierre Boufflet, Sebastian Wood, Jessica Wade, John Moriarty, Eliot Gann, Erin L. Ratcliff, Christopher R. McNeill, Henning Sirringhaus, Ji-Seon Kim, Martin Heeney

Research output: Contribution to journalArticlepeer-review

204 Scopus citations

Abstract

© 2015 American Chemical Society. 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.
Original languageEnglish (US)
Pages (from-to)6866-6879
Number of pages14
JournalJournal of the American Chemical Society
Volume137
Issue number21
DOIs
StatePublished - May 21 2015
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): CRG-1-2012-THO-015
Acknowledgements: This work was supported by EPSRC grants EP/G060738/1 and EP/K029843/1, a KAUST Competitive Research grant under agreement no. CRG-1-2012-THO-015, and the Australian Research Council (FT100100275, DP130102616). We thank Dr. Scott E. Watkins (CSIRO Melbourne) for the PESA measurements. Part of this research was undertaken on the SAXS/WAXS beamline at the Australian Synchrotron, Victoria, Australia.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

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