title: Dialkoxybithiazole: a new building block for head-to-head polymer semiconductors.
abstract: Polymer semiconductors have received great attention for organic electronics due to the low fabrication cost offered by solution-based printing techniques. To enable the desired solubility/processability and carrier mobility, polymers are functionalized with hydrocarbon chains by strategically manipulating the alkylation patterns. Note that head-to-head (HH) linkages have traditionally been avoided because the induced backbone torsion leads to poor π-π overlap and amorphous film microstructures, and hence to low carrier mobilities. We report here the synthesis of a new building block for HH linkages, 4,4'-dialkoxy-5,5'-bithiazole (BTzOR), and its incorporation into polymers for high performance organic thin-film transistors. The small oxygen van der Waals radius and intramolecular S(thiazolyl)···O(alkoxy) attraction promote HH macromolecular architectures with extensive π-conjugation, low bandgaps (1.40-1.63 eV), and high crystallinity. In comparison to previously reported 3,3'-dialkoxy-2,2'-bithiophene (BTOR), BTzOR is a promising building block in view of thiazole geometric and electronic properties: (a) replacing (thiophene)C-H with (thiazole)N reduces steric encumbrance in -BTzOR-Ar- dyads by eliminating repulsive C-H···H-C interactions with neighboring arene units, thereby enhancing π-π overlap and film crystallinity; and (b) thiazole electron-deficiency compensates alkoxy electron-donating characteristics, thereby lowering the BTzOR polymer HOMO versus that of the BTOR analogues. Thus, the new BTzOR polymers show substantial hole mobilities (0.06-0.25 cm(2)/(V s)) in organic thin-film transistors, as well as enhanced I(on):I(off) ratios and greater ambient stability than the BTOR analogues. These geometric and electronic properties make BTzOR a promising building block for new classes of polymer semiconductors, and the synthetic route to BTzOR reported here should be adaptable to many other bithiazole-based building blocks.
authors: Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors: Xugang
authors: X
authors: Guo
authors: Jordan
authors: J
authors: Quinn
authors: Zhihua
authors: Z
authors: Chen
authors: Hakan
authors: H
authors: Usta
authors: Yan
authors: Y
authors: Zheng
authors: Yu
authors: Y
authors: Xia
authors: Jonathan W
authors: JW
authors: Hennek
authors: Rocío Ponce
authors: RP
authors: Ortiz
authors: Tobin J
authors: TJ
authors: Marks
authors: Antonio
authors: A
authors: Facchetti
mesh_terms: D000478:Alkylation; D015394:Molecular Structure; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D012666:Semiconductors; D012995:Solubility; D013844:Thiazoles / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D011108:Polymers; D013844:Thiazoles