In situ synthesis of poly(3,4-ethylenedioxythiophene) in the presence of toluene sulfonate ester thermal initiators

Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most studied conjugated polymers due to its unique electrical and optical properties. While many recent studies focus on device applications, some still explore new approaches to improve its processability. Herein, we present the first in-situ synthesis and characterization of PEDOT using a series of p-toluene sulfonate alkyl esters as non-salt, thermally latent initiators. The diversity of alkyl toluene sulfonates enabled an in-depth investigation of the polymerization mechanism and identification of key intermediates involved in initiation and propagation. Our findings suggest that, rather than undergoing heterolytic dissociation into ions, alkyl toluene sulfonates dissociate homolytically through single electron transfer (SET) with the EDOT monomer. By optimizing the EDOT/initiator ratio, solvent, and temperature, we successfully prepared PEDOT thin films. These films were characterized using FT-IR, NMR, AFM, GPC, MALDITOF, XRPD, and XPS, and the results were compared with commercial PEDOT:PSS. Additionally, electrical conductivity, carrier density, and carrier mobility of the films were evaluated through van der Pauw Hall-effect measurements, highlighting the potential of this approach as a processable alternative to conventional PEDOT: PSS.