Electrical Memory Properties And Synthesis Of Hyperbranched Polyimide

In recent decades, polymer memory devices have received significant attention, since they exhibit high mechanical strength, good processability, flexibility, low-cost potential, and the three-dimensional (3D) multi-stack layer structures. These advantages of polymer memories can meet the requirements for the development of the next generation memory devices which need the high storage density, fast write or read speed, and multilevel designs. And completely different from that of the traditional silicon-based memory cells, which store data by encoding each device as "0" or "1", polyimide memory achieves information storage based on the bistability of the material, for instance the high and low electrical conductivity response to an applied voltage. This feature makes polyimide as one of the most promising candidates for the development of the next generation memory devices. By introducing various different electroactive moieties such as carbazole, triphenylamine, anthracene, tetracene, into the polyimide chain, different types of memory effects have been realized. However, previous research works were mainly focused on the linear polyimide. Few attentions have been paid to the three-dimensional spatial structure of the polyimide itself. Hyperbranched polymers with three-dimensional dentritic architectures exhibit unique chemical and physical properties and have attracted widespread interests in various fields including coatings, drug delivery, gas separation, magnetics and optoelectronics. However, the exploration of hyperbranched polymers as information storage materials such as electrical memory is rarely reported.In this study, we report the synthesis and characterization of novel hyerbranched polyimide containing TPA moieties based on a tetrafunctional monomer, N,N,N’,N’-tetrakis(4-aminophenyl)benzidine (TEAPBD). A hyperbranched polyimide (6F-TEAPBD PI) containing TPA moiety as the electron donating group and6FDA unit as the electron accepting group was synthesized in our present work. The polymer shows irreversible electrical switching behavior at a threshold voltage of about2V with an ON/OFF current ratio at around300. Sandwiched devices (Au//(6F-TEAPBD PI)//ITO) using the synthesized polyimide as the active layer fulfill the requirements of non-volatile and WORM memory. The electrical memory effect observed in the current system was interpreted by the electric-field-induced hole transporting from TPA moieties to phthalimide units and the subsequent formation of charge-transfer complex...