Kinetic control in the synthesis of highly conductive solution-processable PEDOTs

Abstract

Solution-processable poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymers (CPs) are typically synthesized by oxidatively polymerizing 3,4-ethylenedioxythiophene (EDOT) in the presence of soluble polyanions. However, there is still a lack of comprehensive understanding regarding the reaction kinetics and strategies for controlling them, which hampers the attainment of optimal architectures and functionalities of CPs. Herein, we present experimental evidence showcasing the ultra-rapid kinetics of both the polymerization and doping processes of PEDOT, accompanied by time-independent quality characteristics of PEDOT (molecular weight and doping degree). We further demonstrate that both the chemical reactions and subsequent physical assembly behavior are significantly influenced by the local oxidant concentration on the surface of EDOT droplets. The quality of the PEDOT chain is observed to improve consistently with an increased local oxidant concentration, while also noting an initial decrease and subsequent enlargement in the size of the PEDOT assembly. As a result, the film conductivity of the synthesized PEDOT CP increases steadily by approximately 50-fold from 1.44 × 10⁻² to 6.79 × 10⁻¹ S cm⁻¹. Additionally, the H₂SO₄-driven high conductivity also follows a similar trend to the pristine conductivity, but with a significantly larger disparity of approximately 1700-fold (from 6.76 × 10⁻¹ to 1.15 × 10³ S cm⁻¹).