X-RAY-DIFFRACTION AND OPTICAL STUDIES OF FRACTIONALIZED REGIOREGULAR POLY(3-HEXYLTHIOPHENE)

We report results of structural and photoabsorption studies of regiore gular polyhexylthiophene fractions of different backbone length. Polym er of longer chains have better planarity and higher degree of crystal linity. The vibrational structure in the optical spectrum is more clea rly visible, Increase of conjugation length and decrease of the optica l gap with increasing polymerization degree have been observed. Moreov er, the evolution of the photoabsorption spectra as a function of exte rnal pressure is presented. The spectra red shift with increasing pres sure. The largest shifts have been observed for sample of the longest chains. The results are interpreted in terms of the large interchain c oupling induced by pressure. (C) 1998 Elsevier Science S.A.