In situ neutron reflectivity studies of electroactive films

Abstract

In situ neutron reflectivity measurements on potentiodynamically deposited polybithiophene (PBT) films on Pd electrodes supported on quartz are described. The contrast-variation method allows determination of polymer film structure with high resolution perpendicular to the electrode surface. Both undoped and p-doped PBT films comprised a dense inner region, containing virtually no solvent, and an extended diffuse outer region containing considerable solvent. The p-doped films are slightly more diffuse and thicker than the undoped films. Films held in the p-doped state for an extended period of time retain that structure upon undoping. Neutron reflectivity and coulometric data suggest that p-doped films (at +1.2 V) carry one positive charge for every three thiophene rings.