Novel dye-containing copolyimides: synthesis, characterization and effect of chain entanglements on developed electrospun nanofiber morphologies

A series of aromatic copolyimides (coPIs) derived from pyromellitic dianhydride (PMDA) with two diamines as comonomers 4.4′-oxydianiline (ODA) and 2,6-diaminoanthraquinone (2,6-DAAQ) incorporated in variable proportions were synthesized via a conventional two-step route. The obtained copolyimides were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), fluorescence spectroscopy (FL) and tensile tests, etc. The flexible thin films still possessed fairly good thermal stability and high glass transition temperature (T _g), and exhibited various fluorescence intensities. All PI films exhibited excellent thermal stability without significant decomposition up to 500 °C under nitrogen atmosphere. With the increased bulky anthraquinone substituents in coPI chain, the coPIs showed much higher tensile strength and modulus (improved by 23.3 and 38.4 % respectively), and enhanced fluorescence intensities. The chain entanglements of polymer solutions with different inherent viscosities have been used to elaborate the transition from electrospraying to electrospinning in regard to the developed morphologies of electrospun membranes.