Fluorescence depolarization in poly(p-phenylphenylenevinylene) and related oligomers

The photophysical behavior of poly(p-phenylphenylenevinylene) (PPPV) and several oligomeric model compounds in isotropic and anisotropic samples is investigated. 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 position, 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