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Synthesis and resistive switching characteristics of polyimides derived from 2,7-aryl substituents tetraphenyl fluorene diamines

Yanhua Yang,Jingcheng Xia,Zijun Ding,Youxuan Zheng,Shijin Ding,Yingzhong Shen

Four new symmetric diamines (4,4′-(2,7-diphenyl-9H-fluorene-9,9-diyl)dianiline (TPF-Ph), 4,4′-(2,7-bis(4-(naphthalen-1-yl)phenyl)-9H-fluorene-9,9-diyl)dianiline (TPF-Ph-Na), 4,4′-(2,7-di([1,1′-binaphthalen]-4-yl)-9H-fluorene-9,9-diyl)dianiline (TPF-2Na), and 4,4′-(2,7-bis(3,5-dimethoxyphenyl)-9H-fluorene-9,9-diyl)dianiline (TPF-Ph-OMe)) containing tetraphenyl fluorene (TPF) core were synthesized through Suzuki coupling reaction, the corresponding four polyimides (PI(TPF-Ph), PI(TPF-Ph-Na), PI(TPF-2Na), and PI(TPF-Ph-OMe)) were prepared through polymerization reaction. The electrical memory measurement displayed that PI(TPF-Ph) and PI(TPF-Ph-Na) exhibited volatile dynamic random access memory (DRAM) behaviors, PI(TPF-2Na) possessed volatile static random access memory (SRAM) behavior due to the more distorted structure of 1,1′-binaphthalenyl moiety, and PI(TPF-Ph-OMe) showed non-volatile write-once read-many (WORM) behavior due to the presence of deeper charge traps and higher dipole moment of 3,5-dimethoxyphenyl substituent. They possessed low turn-on switching voltages and the ON/OFF current ratios were between 10 3 and 10 5 with the retention times up 4 × 10 3  s. Quantum simulations about energy levels, electrostatic potential (ESP) surfaces, and dipole moment were used to demonstrate the switching mechanism. The experimental results indicated that the electrical memory behaviors of the synthesized polyimides could be tuned through rational structural modification of the electron donor moiety.