Rheofluorescence studies of poly(p-phenylenevinylene) derivatives in simple shear flow

A novel spectroscopic approach that employs an optically accessible Couette cell has been developed to investigate the effects of a uniform shear field on LEP luminescence. Orientation and deformation in polymer solutions are observed as shear-dependent changes in fluorescence emission. We report the influence of simple shear flow on steady state fluorescence emission from MEH-PPV and two other poly(p-phenylenevinylene) derivatives, in dilute solution and a polystyrene matrix. Rheochromism, a shear-induced red shift of 4-6 nm in spectra recorded at shear rates of 100-1000 s−1, indicates a small extension of conjugated polymer coils. Changes in fluorescence emission intensity as a function of shear rate and observation geometry are attributed to alignment of prolate polymer coils in the flow field.