Luminescence excitation spectroscopy of highly oriented poly (3-octylthiophene)-polyethylene blends

Polarized luminescence spectra of gel-processed blends of poly(3-octylthiophene) and ultra-high molecular weight polyethylene are reported for different excitation energies and for several concentrations of the conjugated polymer. The films are oriented by tensile drawing to a draw ratio of 62. The strong anisotropy of the emission spectra indicates that polyoctylthiophene is very well oriented along the stretching axis. At high concentration stretching induces the orientation of polythiophene aggregates. At low concentration the order and orientation of polyethylene are transferred to the conjugated guest. A mobility edge in the absorption tail is observed. The localized lower energy states show the strongest anisotropy and correspond to the longer conjugation length segments.