Influence of steric configurations in the conjugated polymers using acridine-triazine derivates as green chromophores

Abstract

High-quality polymers with the advantages of chemical modifiability, good morphological stability, and excellent solubility have a wide application in the field of solution-processed organic light-emitting devices. However, the influence of steric configurations in the conjugated polymers has not been explored in detail. Herein, we designed and synthesized two kinds of green conjugated polymers with hyperbranched structure (HGx, x = 1, 5, 8, 10) and linear structure (LG10), respectively, using 10-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)−9,9-dimethyl-9,10-dihydroacridine (Ac-TRZ) as the chromophores, poly(fluorene-carbazole) as the backbone. Particularly, triphenylamine groups were used as the hyperbranched cores. Owing to the large steric hindrance and multi-arm structure, hyperbranched polymers exhibited higher thermal stability (Tg＞110 ℃) and an effective energy transfer process. Regrettably, both kinds of conjugated polymers had low PLQYs and nanosecond-scale excitons lifetime because the 3LE energy levels induced by the backbone were lower than the 3CT energy levels induced by the green units. By calculation, it is found that fluorescent segments connected to the green units had directly changed the electronic structure. Moreover, the films of linear polymers possessed considerable surface roughness. From the above results, it is confirmed that the rational design of steric conformations in the conjugated polymers is very important for perfecting the thermal stability, photophysical properties, and film morphologies.