Tuning Electrical Memory Behavior from Nonvolatile to Volatile by Varying Tethering Positions of the Anthracene Moiety in Functional Polyimides

In this work, three functional polyimides, in which the diaminophenylaminoanthracene (DAPAA) group served as the electron donor and 4,4'-hexafluoroisopropylidene dianhydride (6FDA) served as the electron acceptor, were synthesized and denoted as 1-DAPAA-6FDA, 2-DAPAA-6FDA, and 9-DAPAA-6FDA. The only difference between the three polyimides was that the anthracene group in DAPAA was attached to the nitrogen atom through different tethering positions (1-, 2-, and 9-). Characterization results indicate that the 1-DAPAA-6FDA and 9-DAPAA-6FDA based memory devices exhibit nonvolatile write once read many times memory (WORM) behavior; while the 2-DAPAA-6FDA based memory device exhibits volatile static random access memory (SRAM) behavior. Quantum chemical calculation results indicate that a lower dihedral angle between the anthracene group and the molecular backbone of 2-DAPAA-6FDA caused better coplanar structure for charge transfer (CT) and back CT processes, which accounts for the observed volatile SRAM memory performance. All of the polyimides possess excellent long-term operational stability. This work reveals the possibility of tuning memory behavior by elaborately adjusting the spatial conformation of the electron donor, providing feasible guidance for the design of polymer memory materials.