ELECTRIC-FIELD ASSISTED PHOTODEGRADATION OF SPATIALLY CONFINED POLY(P-PHENYLENEVINYLENE)

The effect of electric fields on the fluorescence decay of block-copol ymers containing poly(p-phenylenevinylene) (PPV) and polynorbornene (p olyNBE) was measured. Electric fields of up to 200 V/mu m do not pertu rb the fluorescence decay profiles when the average size of the PPV bl ock is small (i.e., PPV3-block-polyNBE(200) or PPV3-block-polyNBE(25)) . It appears that for shea isolated PPV segments the electric field ac cessible for these studies does not allow dissociation of photogenerat ed excitons into electron-hole pairs. For larger PPV segments, as in P PV20-block-polyNBE(200), the electric field reduces considerably the f luorescence lifetime and quantum yield. In addition, irradiating the s ample under an electric field changes permanently its fluorescence cha racteristics. Control experiments show that neither irradiation nor th e field alone can degrade the polymer.