Structure of thin films of poly(3,4-ethylenedioxythiophene)

Thin films (50-400 nm) of tosylate-doped poly(3,4-ethylene-dioxy-thio phene) (PEDOT) on various substrates have been studied by grazing inc idence X-ray diffraction, using synchrotron radiation. The material w as found to be highly anisotropic. This is correlated with a strong a nisotropy observed in its optical and electronic properties. The crys talline order is limited, and evidence is found for a paracrystalline structure. A structural model is presented, which corroborates with the optical anisotropy. The effect of heating the material to 200oC was studied. Unlike the situation for other substituted polythiophene s, heating PEDOT increases the crystalline order.