Fluorescence of poly[2-methoxy-5-(2 '-ethylhexoxy)-p-phenylene vinylene]. Effect of pressure in a variety of solid polymeric media

The effect of pressure to 65 kbar has been measured on the steady-state and time-dependent emission of MEH-PPV in seven polymers. Both the shape and i ntensity of the emission spectra vary strongly with pressure. In all blends there is a drop in intensity over the first 20-25 kbar probably in part as sociated with long-range intramolecular electron transfer increased by comp ression. Above 30 kbar some blends show a considerable increase in intensit y in the higher energy region of the spectrum. The time-dependent emission can, in general, be fit using single or multiple exponentials. However, in all but one blend the emission at high energy can be equally well fit using the Forster energy-transfer theory. Those blends that show a significant i ncrease in intensity associated with the higher energy emission at high pre ssure also show an increase in the efficiency of energy transfer. Those ble nds that do not show an increase in energy transfer efficiency show no incr ease in intensity.