Enhanced polarization ratio of electrospun nanofibers with increased intrachain order by postsolvent treatments

Polarized emission that is beneficial to lighting and display applications can be demonstrated by aligning emissive chromophores, which can be achieved using an electrospinning technique. We investigate the photophysical properties of nanofibers based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]/poly(ethylene oxide) blends both with and without postsolvent treatments. Two different solvents were sequentially used in an attempt to extract the insulating electrospinnable polymer and increase the polarization ratio of the nanofiber meshes by molecular reorganization. The polarization ratio of emission from the nanofiber meshes treated with N,N-dimethylformamide (DMF) following treatment with acetonitrile solvents was found to be increased. An increase in the 0-0 emission vibronic intensity relative to that of the 0-1 peak and a reduction in the photoluminescence (PL) bandwidth were found. In addition, the PL decays faster and the parallel component along the nanofiber axis increases after the DMF treatment, indicating that the radiative recombination process becomes faster. Our results consistently show that postsolvent treatment promotes stronger J-aggregate character, with longer coherence lengths of the exciton along the long axis of the nanofibers, due to enhanced intrachain order.