Poly(ethylene oxide)/Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonate) (PEDOT:PSS) Blends: An Efficient Route to Highly Conductive Thermoplastic Materials for Melt-State Extrusion Processing ?

Blends of poly(ethylene oxide) (PEO) with poly(3,4- ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) were investigated for the preparation of electrically conductive films using melt-state extrusion processing techniques. High molecular weight PEO is selected as a melting carrier to enable the extrusion processing of PEDOT:PSS. A drop-casting technique from aqueous solutions is first investigated to produce model PEO/PEDOT:PSS blends and identify the influence of relevant parameters on the final electronic conductivity. A low percolation threshold (approximately 9 wt % PEDOT:PSS into PEO) and high electronic conductivities (10-1000 S/cm) are detected. These performances are correlated to homogeneous blend morphologies and miscibility effects arising from strong PEO/PSS interactions detected by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). Storage time and water ionic content have negative impacts on the electronic conductivity. The procedure was then adapted to prepare PEO-rich blends using twin-screw extrusion at 120 degrees C. A strong negative impact of the thermomechanical treatment was attested for PEO/PEDOT:PSS blends due to phase segregation phenomena induced by extrusion. However, an acidic post-treatment on extruded and molded thin films efficiently restored high electronic conductivities up to 4 S/cm for PEO-rich blends with 40 wt % PEDOT:PSS due to the removal of insulating phases. Such thermoplastic materials were found to be competitive with traditional thermoplastic solutions and thus represent efficient candidates for the development of thermoplastic electrodes using conventional and advanced processing technologies of the plastic industry.