Bromophenoxy Substitution Effect on Thermal and Opto-Electronic Properties of Triphenylamine-Based Co-polyimides

Abstract

The present study reported the synthesis of a series of 4,4'diamino-(4''-p-bromophenoxy)triphenylamine diamine 2 based co-polyimides (Br-TPA co-PIs (A-D))obtained via polycondensation of 2 with a series of dianhydrides. The nucleophilic N-arylation of the 4-(4-bromophenoxy)benzenamine followed by catalytic reduction was used to obtain 2. The synthesized Br-TPA coPIs were characterized by CHN elemental, and FTIR spectral analysis. The optical and redox active properties were examined by the ultraviolet/visible (UV/vis) absorption, photoluminescence emission spectral analysis and cyclic voltammetry respectively. From which it is obvious that Br-TPA coPIs are optical transparent, and deep blue light emissive in the range 465-472 nm with a quantum efficiency of 4.6-7.3 %. The lifetime decay was calculated from the time correlation single photon counting (TCSPC) and found in the range 11.7-12.9 nS. The evaluation of thermal properties via thermogravimetric analysis (TGA) revealed excellent thermal stability of synthesized materials in the range 426-476 & DEG;C. The excellent thermal properties, appreciable processability, shallow HOMO levels (-4.70 eV), low onset oxidation (E onset=0.296 V) and long-lived excited states (12.94 nS decay time) evidently depicted their optoelectronic character, suggesting their use as efficient light emitting layer in light emitting diiodes.