Inducing planarity in redox-active conjugated polymers with solubilizing 3,6-dialkoxy-thieno[3,2-b]thiophenes (DOTTs) for redox and solid-state conductivity applications

Abstract

In this work, we evaluate a series of dioxythienothiophene (DOTT)-based polymers for their charge transport structure–property relationships for both solid-state and electrochemical applications. The family includes: (i) the homopolymer, (ii) two 3,4-ethylenedioxythiophene (EDOT) co-polymers, (iii) a dimethyl ProDOT (DMP) co-polymer, and (iv) a bulky neopentyl dioxythiophene (NeoDOT) co-polymer. We show that all of the soluble DOTT polymers can be oxidized through chemical or electrochemical processes, through the full depletion of their neutral π–π* absorbance. The DOTT homopolymer and DOTT-NeoDOT co-polymer show high degrees of intermolecular ordering according to GIWAXS measurements, however, this order inhibits both chemical and electrochemical oxidation. DOTT-NeoDOT has the highest onset of electrochemical oxidation at 0.3 V vs. Ag/Ag⁺. In comparison, DOTT-BiEDOT has lower degrees of intermolecular ordering and the lowest onset of oxidation at −0.5 V vs. Ag/Ag⁺. Furthermore, this polymer has the highest solid-state conductivity of the family, which approaches 20 S cm⁻¹ after chemical oxidation with the molecular dopant F4TCNQ. This study is the first to report the effects of chemical doping and charge transport on a family of soluble DOTT-based polymers.