Synthesis, characterization, and photophysical properties of dicyanoarylamine‐based semi‐aromatic polymers

Abstract

AbstractIntroductionFluorescent high‐performance polymers have been extensively used in designing optoelectronic devices due to their low cost, excellent thermal stability, high mechanical strength, low flammability, good chemical and radiation resistance, and good electronic properties. While conventional organic luminophores fluoresce strongly in dilute solutions, they suffer from undesirable aggregation‐caused quenching in concentrated solutions and in the solid state due to extensive π‐π stacking interactions and formation of delocalized excitons or excimers. This phenomenon leads to non‐radiative decay thus, decreased fluorescence emission of the material in the solid film state, which significantly limits their real‐world application as solid light‐emitting materials.ObjectivesTo develop new high‐performance polymers with high photo luminescent efficiency, good processability, film‐forming properties, which could potentially be used in the fabrication of optoelectronic devices.MethodsThe preparation of the polyimide DiCN‐PI was carried out by a one‐step, high‐temperature solution imidization method. In this procedure, 1,2,4,5‐cyclohexanetetracarboxylic dianhydride and the diamine were polymerized in 1‐methyl‐2‐pyrrolidinone and γ‐butyrolactone co‐solvent at 180°C for 15 hours in the presence of isoquinoline as catalyst. On the other hand, polyamide DiCN‐PA was synthesized according to the direct phosphorylation polycondensation technique described by Yamazaki from diamine and trans‐1,4‐cyclohexanedicarboxylic acid using triphenyl phosphite and pyridine as condensing agents.Results and DiscussionBoth polymers were soluble in several polar aprotic solvents and exhibited useful levels of thermal stability. The polymers were emissive with PL emission bands around 555 (bluish‐green) and 498 (cyan) nm in dilute 1‐methyl‐2‐pyrrolidinone solutions for polyimide and polyamide, respectively. In the solid film state, the polymers emit light green and yellow colors, which simulate the PL behavior of their aggregated states, thereby demonstrating aggregation‐induced fluorescence changes.ConclusionsThese results indicate that the incorporation of bulky dicyanoarylamine moiety and alicyclic monomer units into the rigid polymer backbones effectively disrupted the planarity of the chain packing which resulted to the fluorescent high‐performance polymers with desired properties for potential optoelectronic applications.