Electric Field Assisted Photodegradation of Spatially Confined Poly(p-phenylenevinylene)

The effect of electric fields on the fluorescence decay of block-copolymers containing poly(p-phenylenevinylene) (PPV) and polynorbornene (polyNBE) was measured. Electric fields of up to 200 V/μm do not perturb the fluorescence decay profiles when the average size of the PPV block is small (i.e., PPV3-block-polyNBE200 or PPV3-block-polyNBE25). It appears that for short isolated PPV segments the electric field accessible for these studies does not allow dissociation of photogenerated excitons into electron-hole pairs. For larger PPV segments, as in PPV20-block-polyNBE200, the electric field reduces considerably the fluorescence lifetime and quantum yield. In addition, irradiating the sample under an electric field changes permanently its fluorescence characteristics. Control experiments show that neither irradiation nor the field alone can degrade the polymer.