Polarized blue photoluminescence of mesoscopically ordered electrospun non-conjugated polyacrylonitrile nanofibers

Conjugated polymers and oligomers that emit polarized light are used as active materials in various optoelectronic device applications, notably organic light-emitting diodes (OLED). Here, we demonstrate the fabrication of electrospun polarized light-emitting fibers from the non-conjugated polymer that can be aligned by a simple heat-streching process. Upon excitation at 340 nm ribbons made from the nanofibres show polarized deep blue luminescence with an anisotropy of 0.37 and a quantum yield of about 31%. Furthermore, they exhibit room temperature green phosphorescences with a lifetime of about 200 ms as well as a delayed deep blue fluorescence resulting from triplet-triplet annihilation (non-coherent photon upconversion) (TTA). Wide and small angle X-ray scattering experiments show that the stretched electrospun fibers are highly aligned with nearly perfect uniaxial orientation within the fabricated ribbons. This results in mechanically robust and flexible, with a high specific tensile strength (534±28) MPa*cm3/g and toughness (79±7) J/g. The combination of efficient polarized deep blue luminescence, room temperature phosphorescence, TTA, mechanically robustness and flexibility of these fibers opens up new avenues for applications of non-conjugated polymers.