UNEXPECTED ORIENTATIONAL EFFECTS IN SPIN-CAST, SUBMICRON LAYERS OF POLY(ALKYLTHIOPHENE)S - A DIFFRACTION STUDY WITH SYNCHROTRON-RADIATION

Sub-micron layers of poly(3-octylthiophene) and poly(3-hexylthiophene) deposited by spin-casting on glass substrates were for the first time investigated by X-ray diffraction using synchrotron radiation. The po lymers have a partial crystalline structure and are, in contrast to bu lk materials, oriented with their side chains parallel to the substrat e surface. Optical absorption spectra obtained from the same samples s how that the conjugation length is related to the crystalline order.