The effect of stereoregularity on the structure of poly(octyl-thiophene) - an x-ray diffraction study

Summary form only given. The structural properties of soluble Poly(3,3´-dioetyl-2,2´bithiophene) (PDOT/sub 2/), a stereoregular analogous of Poly(3-octylthiophene) (POT), have been studied by X-ray diffraction and UV-VIS absorption spectroscopy. The absorption spectra have been acquired in the temperature range 20-190/spl deg/C. The results show that PDOT/sub 2/ is partial crystalline with the polymer chains packing in a parallel manner. The well defined head-to-head, tail-to-tail arrangement of the monomeric units along the polymer chain leads to a crystalline structure differing considerably from the one of POT, Adjacent tail-to-tail coupled thiophene rings are twisted out of plane leading to a short conjugation length as manifest by the absorption maximum, which is blueshifted relative to POT. PDOT/sub 2/ does not show any thermochromic transition. A detailed X-ray analysis involving intensity calculations is under preparation.