Synthesis of Poly(3-substituted thiophene)s of Remarkably High Solubility in Hydrocarbon via Nickel-Catalyzed Deprotonative Cross-Coupling Polycondensation

Abstract

Polythiophenes bearing a siloxane moiety in a substituent at the 3-position are prepared by deprotonative polycondensation of 2-bromo-3-substituted-thiophene with a bulky magnesium amide chloromagnesium 2,2,6,6-tetramethylpiperidine-1-yl lithium chloride salt (TMPMgCl•LiCl) catalyzed by a nickel complex. Deprotonation takes place at 60 °C for 1 h to form the corresponding thiophene magnesium species, which is subjected to the polymerization by addition of 0.1−5 mol % NiCl 2 (PPh 3 )IPr (IPr: 1,3-bis(2,6-diisopropylphenyl)imidazole-2-yl). Polymerization proceeds in a highly regioregular manner, and the molecular weight of the thus-obtained polymer is controllable by the ratio of monomer feed/ catalyst loading to indicate M n of up to 280 000 with narrow molecular weight distribution. Chlorothiophenes are also found to induce polymerization in a deprotonative manner with TMPMgCl•LiCl or nBuLi (the Murahashi coupling polymerization). The obtained polymers bearing a siloxane moiety in the substituent is revealed to be dissolved in a hydrocarbon allowing formation of thin film from hexane.

Synthesis of block copolymers comprised of poly(3‐hexylthiophene) segment with trisiloxane side chains and their application to organic thin film transistor

“…Mori and coworkers reported the synthesis of regioregular polythiophene derivatives having soft siloxane units in the side chains . Indeed, the films of siloxane‐containing polythiophenes showed 2 orders of magnitude smaller Young's modulus and 20 times higher elongation at break than P3HT.…”

Mechanical, Thermal, and Electrical Properties of Flexible Polythiophene with Disiloxane Side Chains

“…High molecular weight and highly regioregular poly(3‐substituted thiophene) with disiloxane moieties (P3SiT) was polymerized by Kumada coupling based on a nickel(II) catalyst (see the Supporting Information for details of the polymerization process) . Synthesized P3SiT had a weight‐average molecular weight ( M w ) of 300k estimated by gel permeation chromatography, and a head‐to‐tail structure of over 99% was confirmed by 1 H NMR (see Figure S2 in the Supporting Information).…”

Rational and practical exfoliation of graphite using well-defined poly(3-hexylthiophene) for the preparation of conductive polymer/graphene composite

“…Figure 3a reveals that low-molecular-weight P3HT ( M n  = 6,000) was the most effective in dispersing graphene. P3HT with molecular weights of more than 40,000 resulted in low graphene concentrations in the dispersion, which might be related to the low solubility of the high-molecular-weight P3HT in toluene1829.…”