SYNTHESIS AND PHYSICAL-PROPERTIES OF REGIOCHEMICALLY WELL-DEFINED, HEAD-TO-TAIL COUPLED POLY(3-ALKYLTHIOPHENES)

We have recently developed a regiospecific synthetic method that produces poly(3-alkylthiophenes) (PAT's) that, for the first time, contain almost exclusively head-to-tail (HT) couplings [1]. Details on the synthesis, NMR characterization of structural regularity, UV-VIS data on solutions and thin films, and preliminary X-ray, electrical conductivity, and thermal data are presented herein. NMR spectral characterization reveals >93% head-to-tail-head-to-tail (HT-HT) couplings in poly(3-butylthiophene) (PBT), poly(3-hexylthiophene) (PHT), poly(3-octylthiophene) (POT), and poly(3-dodecylthiophene) (PDDT). In the UV-VIS, these PAT's show lower energy absorption maximum shifts of up to 14 nm in solution, 46 nm in the solid state, and other intense lower energy peaks with shifts of up to 129 nm (609 nm) from PAT's prepared by the usual methods. X-ray analysis of unoriented (as cast) thin films of PHT on glass indicate a much more ordered structure than PHT made from FeCl3. It also appears that our unoriented PHT is at least as ordered as stretch oriented PHT. Preliminary maximum room temperature electrical conductivity values for PAT's (doped with I2) are 1000 S cm-1 for PDDT, 200 S cm-1 for POT, and 60 S cm-1 for PHT. Thermal analysis of POT prepared by this method is also presented and these samples are found to be highly crystalline.