Abstract
Spectroscopic and photophysical properties of two p-phenylenevinylene (PV) trimers, 2,5-substituted diheptyl-( p-phenylenevinylene) and di-[(2-ethylhexyl)oxy]-( p-phenylenevinylene), were studied using absorption spectroscopy, fluorescence and laser flash photolysis. The change from alkyl to alkyloxy groups red-shifts the absorption and fluorescence bands. The rate of internal conversion is independent of the substitution, whereas alkyloxy substitution increases the S 1 ⇝ T 1 intersystem crossing rate by an order of magnitude. The relevance for the behaviour of conjugated PPV polymers is discussed. For diheptyl-PV, a sample having ca. 3% of the cis-configuration was also studied. Comparison between the all- trans and the cis-contaminated samples revealed no significant differences in their photophysical properties.
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