PHASE-SEPARATION IN POLYANILINE WITH NEAR-FIELD SCANNING OPTICAL MICROSCOPY

We report the studies of conjugated polymers, polyaniline thin films, with a near-field scanning optical microscope. Because of the absorpti on variation in different oxidation states, transmission-mode nearfiel d scanning optical microscope images were employed to map out the dist ribution of the oxidation states on a submicrometer scale. When the ne ar-field wavelength is varied (between 632.8 and 543.5 nm), the phase separation between the oxidized and the reduced repeated units, with d omain sizes on a nanometer-length scale, is observed. (C) 1997 Optical Society of America.