Investigation of thermal and fluorescent properties of benzoxazole-linked triphenylamine-based co-polyimides

A series of novel fluorescent co-polyimides are obtained by combining N¹-(4-aminophenyl)-N¹-(4-(benzo[d]oxazol-2-yl) phenyl) benzene-1,4-diamine and 4,4′-oxydianiline with four aromatic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 4,4′-oxydiphthalic anhydride, and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride following conventional polycondensation method. The resultant co-polyimides are characterized by elemental, Fourier transform infrared spectral analysis and gel permeation chromatography. All newly prepared polyimides (PIs) exhibit shallow highest occupied molecular orbital energy levels in the range of −4.47 to −4.98 eV and have reasonable optical bandgaps. The photoluminescence spectral analysis shows blue to green emission in solution form. Thermal and solubility properties reveal that the PIs with pendant 4-(benzo[d]oxazol-2-yl group linked to triphenylamine unit in polymer backbone impart not only good thermal stability but also appreciable solubility making these new co-polyimides versatile for multipurpose usage.