Compatibility and phase-structure dependence on the conductivity in blends of poly(3-octylthiophene)

We have investigated blends of poly(3-octylthiophene) (POT) with polycarbonate (PC), poly(phenylene oxide) (PPO), polyethylene (PE) and poly(ethylene-co-butyl acrylate) (EBA). Polyethyleneglycol (PEG) has been added to POT/PE- and POT/EBA-blends. Miscibility has been examined with DSC, DMTA and FTIR. Morphology has been investigated with SEM-microscopy. Comparisons with conductivity data from doped samples show that the conductivity is highly dependent on the phase structure. However, the examined blends show no molecular miscibility as observed with DSC or DMTA. Promising results have been obtained in the case of the PPO/POT blends. These blends show conductivities up to approximately 3 S/cm when doped. Shifts of the POT absorbances in FTIR indicate interactions between POT and PPO or changes in the conformational structure of POT. The addition of PEG to PE/POT or EBA/POT decreases the size of the POT-grains and causes the conductivity to increase several orders of magnitude indicating that PEG has a compatibilizing effect.