The photophysical behavior of poly(p-phenylphenylenevinylene) (PPPV) and several oligomeric
model compounds in isotropic and anisotropic samples is investigated by means of polarized fluorescence
spectroscopy. As long as excitation energy transfer and mutual alignment are considered, the behavior of
PPPV can be modeled by a chain consisting of a distribution of independent oligomeric segments. The
results of fluorescence polarization, e.g., the nonzero value of r in isotropic PPPV, cast doubt on the application
of the semiconductor band model but favor an interpretation of spectroscopic properties in terms of molecular
transitions. The orientation coefficients of the oligomers and of PPPV in stretched polyethylene are determined.
The change of fluorescence spectra of oriented PPPV in stretched polyethylene demonstrates directly that
conformational changes of the macromolecule influence the pathway of energy transfer.