Abstract
This paper reports the synthesis of D-A polymers containing 1,2-dithienylethene (DTE) units via palladium-catalyzed direct arylation polymerization (DArP). The reaction of dibromoisoindigo (1-Br) and DTE (2-H), in the presence of Pd2(dba)3·CHCl3 (0.5 mol%), P(2-MeOC6H4)3 (L1) (2 mol%), pivalic acid (1 equiv) as catalyst precursors, and Cs2CO3 (3 equiv) as a base affords poly(1-alt-2) with a high molecular weight (Mn up to 44,900). Although, it has been known that monomers, with plural C–H bonds, tend to form insoluble materials via direct arylation at undesirable C–H positions; the reaction of 1-Br and 2-H cleanly proceeds without insolubilization. The resulting polymer has a well-controlled structure and exhibits good charge transfer characteristics in an organic field-effect transistor (OFET), compared to the polymer produced by Migita–Kosugi–Stille cross-coupling polymerization. The DArP product displays an ideal linear relationship in the current–voltage curve, whereas the Migita–Kosugi–Stille product shows a VG-dependent change in the charge mobility.
Highlights
Introduction πConjugated polymers with donor–acceptor combinations of repeated units (D-A polymers) often exhibit a high device performance in organic field-effect transistors (OFETs) and thin-film solar cells [1,2,3,4]
To understand the reasons behind the large variation in device performance depending on molecular weight, polymer thin films formed on an OTS-treated substrate were investigated by grazing incidence wide-angle X-ray scattering (GIWAXS) and atomic force microscopy (AFM)
We have described the synthesis of D-A polymers containing 1,2-dithienylethene (DTE) units via palladium-catalyzed direct arylation polymerization (DArP)
Summary
The reaction was conducted with of solvents (Scheme 1). When the reaction was carried out in toluene at 100 C, the reaction mixture into a dark mass. THF was less effective as a solvent, giving a low-molecular weight polymer (Mn = 7400) The molecular weight increased in 2-MeTHF (Mn = 22,700) (run 3), and when. Unlike the reaction in toluene, the reaction n = 44,900 was obtained in a recovery rate of 63% (run 3a). Unlike the reaction in toluene, the reaction system liquidity in in 2-MeTHF. ◦ C using 1-Br (0.20 mmol) and 2-H (0.20 mmol), Pd (dba) ·CHCl (0.5 mol%), Reactions at 100. L1 (2 mol%), Cs2 CO3 (0.60 mmol), and pivalic acid (0.20 mmol) in toluene (0.40 mL) unless otherwise stated
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