Ambient Direct Arylation Synthesis of Thienothiophene Based Copolymers with Mixed Alkoxy and Oligoether Side Chains

Licentiate thesis, 2025

Side-chain engineering is a powerful tool for tuning physical properties of conjugated polymers. Here, the synthesis of thienothiophene-based copolymers with mixed oligoether and alkoxy side chains, p[(g₃TT-T2)-ran-(a₁₀TT-T2)], by ambient direct arylation polymerization is described. The composition and molecular weight of the copolymers were 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 which is nearly twice that of p(g₃TT-T2). Organic electrochemical transistors with a NaCl aqueous electrolyte feature a high figure of merit of 1195 F cm⁻¹ V⁻¹ s⁻¹ thanks to a high volumetric capacitance of 414 F cm^-3. Evidently, the introduction of a minor fraction of alkoxy side chains is a viable route for improving the electrical properties of mixed ionic-electronic conducting polymers. Additionally, the challenge of film delamination during the in-situ electrochemical nanoindentation is overcome by surface modification of the indium tin oxide (ITO) substrate.