Ambient direct arylation synthesis of thienothiophene based copolymers with mixed alkoxy and oligoether side chains

Conjugated polymers with both oligoether and alkoxy side chains are an emerging type of organic mixed ionic-electronic conductor. Here, direct arylation polymerization is introduced as a viable synthetic route for such materials. The composition and molecular weight of the synthesized thienothiophene-based random copolymers are determined with high-temperature ¹H NMR spectroscopy. Chemical and electrochemical doping of the copolymers reveal that the introduction of a minor fraction of alkoxy side chains results in materials with a highly promising set of electrical and mechanical properties. A copolymer with an alkoxy side-chain fraction of 12% features an electrical conductivity of 390 S cm^-1 and a charge-carrier mobility of more than 3 cm² V^-1 s^-1. Organic electrochemical transistors with a NaCl aqueous electrolyte feature a high figure of merit of 1313 F cm^-1 V^-1 s^-1 thanks to a high volumetric capacitance of 417 F cm^-3. Evidently, the introduction of a minor fraction of alkoxy side chains is a viable route for improving the electrical properties of organic mixed ionic-electronic conductors.