Influence of synthetic pathway, molecular weight and side chains on properties of indacenodithiophene-benzothiadiazole copolymers made by direct arylation polycondensation

Desiree Adamczak, Andrea Perinot, Hartmut Komber, Anna Illy, Sandra Hultmark, Bianca Passarella, Wen Liang Tan, Sebastian Hutsch, David Becker-Koch, Charlotte Rapley, Alberto D. Scaccabarozzi, Martin Heeney, Yana Vaynzof, Frank Ortmann, Christopher R. McNeill, Christian Müller, Mario Caironi, Michael Sommer

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5 Scopus citations

Abstract

Atom-economic protocols for the synthesis of poly(indacenodithiophene-alt-benzothiadiazole) (PIDTBT) are presented in which all C-C coupling steps are achieved by direct arylation. Using two different synthetic pathways, PIDTBT copolymers with different side chains (hexylphenyl, octylphenyl, dodecyl, methyl/2-octyldodecylphenyl, 2-octyldodecylphenyl/2-octyldodecylphenyl) and molecular weight (MW) are prepared. Route A makes use of direct arylation polycondensation (DAP) of indacenodithiophene (IDT) and 4,7-dibromo-2,1,3-benzothiadiazole (BTBr2) leading to PIDTBT in high yields, with adjustable MW and without indications for structural defects. Route B starts from a polyketone precursor also prepared by DAP following cyclization. While route B allows introduction of asymmetric side chains at the IDT unit, polymer analogous cyclization gives rise to defect formation. The absorption coefficient of PIDTBT with alkylphenyl side chains made by route A increases with MW. Field-effect hole mobilities around ∼10-2 cm2 V-1 s-1 are molecular weight-independent, which is ascribed to a largely amorphous thin film morphology. PIDTBT with linear dodecyl side (C12) chains exhibits a bathochromic shift (20 nm), in agreement with theory, and more pronounced vibronic contributions to absorption spectra. In comparison to alkylphenyl side chains, C12 side chains allow for increased order in thin films, a weak melting endotherm and lower energetic disorder, which altogether explain substantially higher field-effect hole mobilities of ∼ 10-1 cm2 V-1 s-1.
Original languageEnglish (US)
Pages (from-to)4597-4606
Number of pages10
JournalJournal of Materials Chemistry C
Volume9
Issue number13
DOIs
StatePublished - Apr 7 2021
Externally publishedYes

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Generated from Scopus record by KAUST IRTS on 2023-02-14

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