Asymmetric isomerization: an efficient strategy to tune the electrical resistive memory behaviors of functional polyimides containing N-phenylcarbazole moieties

Abstract

To elucidate the influence of spatial structure on memory behavior, three isomeric polyimides (PIs), PI-3,6-DAPCz-6FDA, PI-3,4 0 -DAPCz-6FDA, and PI-2 0 ,4 0 -DAPCz-6FDA, for electrical memory applications are designed and synthesized. Current-voltage characteristics indicate that the three isomeric PIs display vastly deviating memory effects. PI-3,6-DAPCz-6FDA and PI-3,4 0 -DAPCz-6FDA both show volatile static random access memory (SRAM) behavior, while PI-2 0 ,4 0 -DAPCz-6FDA exhibits a non-volatile write once read many times (WORM) memory characteristic. The mechanisms associated with the memory effect were analyzed based on molecular simulation results. PI-3,6-DAPCz-6FDA possesses the best structural coplanarity, which greatly facilitates its charge transfer (CT) and back CT process, leading to the volatile SRAM feature. However, PI-2 0 ,4 0 -DAPCz-6FDA exhibits more torsional structures, which consequently prohibits the back CT process, explaining its non-volatile behavior. Additionally, the three isomeric PIs show fast transient responses. The results show the importance of the spatial structure on polymer memory and the viability of adjusting memory types by isomerization.

Synthesis of a Novel Rigid Semi-Alicyclic Dianhydride and Its Copolymerized Transparent Polyimide Films’ Properties

“…Some researchers have revealed that it is possible to increase the free volume of the molecular chain and increase the distance between the molecular chains by introducing solubilizing groups (such as a –CF 3 group, carbonyl group, and benzene ring side group) in the main chain. These features of the structures facilitate the easier entrance of small solvent molecules into the molecules and improve their solubility [ 36 , 37 , 38 , 39 ]. Therefore, the copolymerized CPIs also have an excellent solubility.…”

“…On the other hand, the –CF 3 and phenyl side group could further enhance the thermal properties [ 36 , 37 , 38 ]. Moreover, the –CF 3 and phenyl side groups can increase the distance between molecular chains to reduce the chain packing to hinder the formation of the CTC effect [ 39 ]. These features could remarkably improve the optical and solubility properties of CPI films.…”

Regulating the electrical resistive switching behaviors of polyimides through different steric hindrance substituents on 2,7-position of tetraphenyl fluorene diamines moieties

“…Up to now, through the polycondensation reactions of different electron-donating (D) moieties containing triphenylamine, [10][11][12] , carbazole, [11][12][13][14] ferrocene, 15 pyrrole, 16 oxadiazole, 17 triazole, 18 porphyrin, 19,20 and thiophene, 21 with the electron-accepting (A) moieties, functional PIs with multifarious memory deeds, involving dynamic random access memory (DRAM), 20 static random access memory (SRAM), 17 flash, 15,22 and write-once read-many-times memory (WORM), 16,23 have been wide researched. Meanwhile, molecular structure could be regulated through the introduction of flexible linkages, 24,25 fluorine atoms, 26 bulky pendant groups, 27 and unsymmetrical units.…”

Novel carbazole-based donor-isoindolo[2,1-a]benzimidazol-11-one acceptor polymers for ternary flash memory and light-emission

“…The latter utilizes the tendency of neighbouring carbazole groups to form a face-to-face conformation that could facilitate charge carriers hopping through under an applied voltage, leading to a high-conductivity state, 14,26,29,30 while the former fully utilizes the property of hole transporting, the advantage of rigid planar structure, and the ease of controlling the photoelectron performance at molecule level by introducing various acceptor directly to the backbone of the carbazole group. 24,31 PIs have been widely used as acceptor because of the excellent thermal, chemical and electro properties and the feasible functionalization of molecule to tune these properties. The phthalimide segment of PI possesses strong ability of electron withdrawing and would achieve a conductive charge transfer (CT) state under applied electric eld by linking with an electron donor to form a donor-acceptor (DA) system of a polymer, which could lead to a non-volatile behaviour of a memristor.…”