Effect of Uniaxial Stretching on Structural Properties of Poly(3-Alkylthiophenes)

The influence of uniaxial stretching on the molecular structure of poly(3-alkylthiophenes) was studied with the use of X-ray diffraction. Three poly(3-alkylthiophenes), namely these containing n-hexyl, n-octyl and n-decyl groups, were investigated. The samples were oriented by stretching and the diffraction patterns for two geometries of scattering were obtained for undoped samples. The comparison of experimental diffraction data for unoriented and oriented samples, gives information about the role of the side chains in the changes of molecular conformation induced by stretching of the polymer sample. The main conclusion of our work is that the process of orientation induces similar phenomena in all samples studied, but the structural and conformation changes depend on the side chain length: the shorter the alkyl substituent, the easier the straightening of the main polymer chain. The authors suggest that uniaxial stretching of poly(3-alkylthiophenes) changes the degree of main chain planarity. This effect can influence the π-conjugation in polymer system, which may have great importance for any future application of poly(3-alkylthiophenes).