Structure-directed growth of high conductivity PEDOT from liquid-like oxidant layers during vacuum vapor phase polymerizationElectronic supplementary information (ESI) available: Calculated vapor pressures of pyridine, water and n-butanol as a function of temperature in Fig. S1. See DOI: 10.1039/c2jm32281a

Vapor phase polymerization (VPP) is at the forefront for synthesizing high conductivity poly(3,4-ethylenedioxythiophene) (PEDOT) as an alternative to indium tin oxide (ITO). Little attention, however, has been directed to the oxidant layer used in the polymerization process. In this study the observation of an oxidant layer (oxidant + PEG-PPG-PEG) possessing liquid-like properties during the vacuum synthesis of PEDOT is reported. This is in contrast to the other oxidant layer variants studied which are observed as solid (pristine oxidant) or gel-like (oxidant + pyridine). Tailoring of the liquid-like properties leads to confluent PEDOT films with a conductivity of 2500 S cm −1 , placing this PEDOT within the conductivity range of commercially available ITO. Building on the liquid-like observation, XPS and ToF-SIMS experiments reveal that PEDOT growth is via a bottom-up mechanism with transportation of new oxidant up to the forming PEDOT layer. Highly conductive PEDOT is produced by the capillary flow of liquid oxidant around the PEDOT particles which allows the monomer to access fresh oxidant during the V-VPP process. This oxidant movement provides the mechanism by which PEDOT achieves conductivities comparable to ITO, namely > 2500 S cm −1 .