New Donor−Acceptor Random Copolymers with Pendent Triphenylamine and 1,3,4-Oxadiazole for High-Performance Memory Device Applications

Terpolymerization of Ethylene with Hexene and Styrene Derivatives by Half-Sandwich Scandium Catalyst

The terpolymerization of ethylene with hexene and styrene derivatives was achieved with a rare earth metal catalyst (C5Me4SiMe3)Sc(CH2C6H4NMe2-o)2 to prepare functional polyethylene. The catalyst system exhibited high activity in the terpolymerization of ethylene with hexene and amine-substituted styrene, affording terpolymers a moderate molecular weight and a unimodal molecular weight distribution. In addition, the comonomer content of the terpolymers can be controlled by changing the feeding ratio of monomers. The aliphatic region of the 13C NMR spectra reveals that the structural units of the comonomers are separately incorporated into the polyethylene backbone. Terpolymers containing styrene derivatives exhibit enhanced tensile strength and significantly improve hydrophilic properties.

Zn(ii) detection and biological activity of a macrocycle containing a bis(oxadiazole)pyridine derivative as fluorophore

The synthesis, photochemical properties, biological effects and the X-ray crystal structure of a fluorescent polyamine macrocycle L are reported. L is a polyamine cyclophane macrocycle in which 2,6-bis(5-(2-methylphenyl)-1,3,4-oxadiazol-2-yl)pyridine (POXAPy) acts as a fluorescent sensor and the polyamine as a metal ion binding unit. L performs as a PET-mediated chemosensor, with a maximum emission wavelength close to 360 nm. This gives rise to a signal that is visible to the naked eye in the blue visible range. L is able to detect the Zn(ii) and Cd(ii) metal ions in an aqueous solution at pH = 7, with the coordination of the ions switching the emission ON through a CHEF effect. In contrast, paramagnetic metal ions like Cu(ii) and Ni(ii) completely quench the already low emission of L at this pH value. L affects the cell survival of a leukemic cellular model (U937) at micromolar concentrations with cell death starting after only 24 h of exposure; starting from a final concentration of 5 μM, L almost completely abrogates the survival of the leukemic cells over 72 h, with a mechanism that is compatible with a genomic DNA interaction.

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

Three novel donor-acceptor polymers (PCz0, PCz2 and PCz4) based on 9-(9-heptadecanyl)-9H-carbazole and isoindolo[2,1-a]benzimidazol-11-one with fluorine substituents (0, 2 and 4) on the acceptor unit were prepared by Suzuki polymerization. The synthesized polymers were studied by theoretical calculation, and optical and electrochemical characterizations to further investigate the performance of memory storage and light-emission. The memory devices of the three polymers all exhibited obvious ternary flash behavior with total ON/OFF state current ratio around 104 and threshold voltages below 3.0 V, with no other blending or doping. Bright emissions of an electroluminescence device based on PCz0 was obtained at 556 nm, the maximum brightness was 2006 cd m-2 with EQE of 0.21%. The results suggested that polymers with the structure of carbazole-based donor as backbone and isoindolo[2,1-a]benzimidazol-11-one segment as acceptor could be excellent materials for memory storage and light-emitting applications with further investigation and could be used for further design of other new polymer systems.

Donor-Acceptor Core-Shell Nanoparticles and Their Application in Non-Volatile Transistor Memory Devices

Donor-acceptor crosslinked poly[poly(ethylene glycol) methyl ether-methacrylate]-block-poly[1,1'-bis(2-ethylpentyl)-6-methyl-6'-(5-methyl-3-vinylthiophen-2-yl)-[3,3'-biindoline]-2,2'-dione] (poly(PEGMA)_m -b-poly(VTIID)_n ) nanoparticles with various vinylthiophene donor/isoindigo acceptor ratios are synthesized successfully. The prepared nanoparticles have uniform sizes and well-defined core-shell nanostructures. The intramolecular charge transfer is effectively enhanced due to the incorporation of acceptor groups after the crosslinking reaction. A transistor memory device is assembled using the synthesized polymer and has nonvolatile flash-type memory and amphiphilic trapping behavior. The optimized devices exhibit a significant memory window of approximately 38 V, a retention ability of over 10⁴ s, and an endurance of at least 100 cycles. This study examines multiple applications of crosslinked core-shell nanoparticles, which demonstrates their promise as charge-storage dielectric materials for use in organic memory devices.

In Situ Monitoring of Fluorescent Polymer Brushes by Angle-Scanning Based Surface Plasmon Coupled Emission

Fluorescent polymers have attracted interest in many fields such as sensing, diagnostics, imaging, and organic electronic devices. Real-time techniques to monitor and understand the polymerization process are important for obtaining controllable fluorescence polymers. We present a new technique to in situ monitor the growth process of fluorescent polymer brushes by using angle-scanning based surface plasmon coupled emission (AS-SPCE) approach during electrochemically mediated atom-transfer radical polymerization. The polymer thickness was determined by modeling the location of SPCE emission angle(s) with theoretical calculation. The advantages of unique angle distribution patterns, thickness dependence and effective background rejection of AS-SPCE guarantee the success in the real-time investigation for controllable fabrication of fluorescent polymers.

Redox gated polymer memristive processing memory unit

Memristors with enormous storage capacity and superior processing efficiency are of critical importance to overcome the Moore’s Law limitation and von Neumann bottleneck problems in the big data and artificial intelligence era. In particular, the integration of multifunctionalities into a single memristor promises an essential strategy of obtaining a high-performance electronic device that satisfies the nowadays increasing demands of data storage and processing. In this contribution, we report a proof-of-concept polymer memristive processing-memory unit that demonstrates programmable information storage and processing capabilities. By introducing redox active moieties of triphenylamine and ferrocene onto the pendants of fluorene skeletons, the conjugated polymer exhibits triple oxidation behavior and interesting memristive switching characteristics. Associated with the unique electrochemical and electrical behavior, the polymer device is capable of executing multilevel memory, decimal arithmetic operations of addition, subtraction, multiplication and division, as well as simple Boolean logic operations.

Though designing conductive polymers for memory devices is attractive for future low-cost flexible electronics, a proof-of-concept device has yet to be realized. Here, the authors report a redox-gated polymer memristive processing unit with programmable multilevel storage and logic functionalities.

Solvents Effects on Film Morphologies and Memory Behavior of a Perylenediimide-Containing Pendent Polymer

The large polydispersity index of functional pendant polymers has hindered their application in semiconductors. Herein, a novel pendant polymer with perylenediimide (PDI) in the side chains was successfully synthesized through ring-opening metathesis polymerization (ROMP) with a very low polydispersity index. The synthesized polymers were spin-coated on indium tin oxide (ITO) substrate by using a mixture of 1,2-dichlorobenzene (o-DCB) and methanol (MeOH) solvents. The surface morphologies and intermolecular π-π stacking of the fabricated film could be adjusted through tuning of the ratio of o-DCB and MeOH, and thus, the sandwich-structured device of ITO/polymer/aluminum exhibited different electrical behavior. The threshold voltages of the devices decreased as the MeOH content was increased from 0 to 30 % (v/v); however, the device changed from being unrewritable to rewritable if the MeOH content was increased to 40 %; a probable mechanism for this process is discussed. It is hoped that this new idea of synthesizing narrow polydispersity index pendant polymers, and the fabrication of high-quality films through the use of a mixture of solvents could allow high-performance memory devices to be prepared in the future.

π-Stacked poly(vinyl ketone)s with accumulated push–pull triphenylamine moieties in the side chain

Poly(vinyl ketone)s bearing push–pull triphenyamine moiety indicated remarkable absorption hypochromism, reduced redox potentials, and emission red shifts due to a π-stacked conformation.

A WORM type polymer electrical memory based on polyethersulfone with carbazole derivatives

A series of high-performance polyethersulfone, which had pendent carbazole moieties (Cz-PES 1–3), have been designed and successfully synthesized for an application in a write-once read-many type memory device as the active polymer layer. The memory performance can be tuned by changing the substituent in the Cz derivatives units. Cz-PES 3 with excellent thermal properties ( Tg = 185°C and Td = 378°C) exhibits the best memory performance. For Cz-PES 3-based device indium tin oxide/Cz-PES 3/aluminum, the turn-on voltage is 2.5 V and the ON/OFF current ratio is higher than 106. Moreover, the data can be maintained for longer than 3 × 105 s once written and can be read for more than 450 cycles under a reading voltage of 1.0 V at ambient conditions. Thus Cz-PES 3 can serve as an excellent memory material in the data storage field of next generation.

Design of triphenylamine appended anthracene derivatives: electro-polymerization and their electro-chromic behaviour

Three derivatives of anthracene as a core interior with terminal one or two triphenylamine sides have been designed and developed to achieve a smart metal free electrochromic materials.

Organic Electronic Memory Devices

With the rapid development of the electronics industry in recent years, information technology devices, such as personal computers, mobile phones, digital cameras and media players, have become an essential part of our daily life. From both the technological and economic points of view, the development of novel information storage materials and devices has become an emergent issue facing the electronics industry. Due to the advantages of good scalability, flexibility, low cost, ease of processing, 3D-stacking capability and high capacity for data storage, organic-based electrical memory devices have been promising alternatives or supplementary devices to conventional inorganic semiconductor-based memory technology. The basic concepts and historical development of electronic memory devices are first presented. The following section introduces the structures and switching mechanisms of organic electronic memory devices classified as transistors, capacitors and resistors. Subsequently, the progress in the field of organic-based memory materials and devices is systematically summarized and discussed. Finally, the challenges posed to the development of novel organic electronic memory devices are summarized.

Multilevel conductance switching of a memory device induced by enhanced intermolecular charge transfer

The modification of the terminal electron-donating groups induces a critical change in molecular aggregation and the intermolecular charge-transfer effect of the symmetric D-A1-A2-A1-D molecules that correlate with an addressable variation of memory performance from binary to ternary.

Substituent and Charge Transfer Effects on Memory Behavior of the Ambipolar Poly(triphenylamine)s

A series of poly(triphneylamine)s (CN-PTPA, 2CN-PTPA, 3CN-PTPA, and NO2-PTPA) with pendent acceptors (cyano, dicyanovinyl, tricyanovinyl, and nitro) have been readily synthesized by oxidative coupling polymerization using FeCl3 as oxidant. The tunable memory properties of the ITO/polymer/Al sandwiched memory devices including DRAM, SRAM, and WORM could be achieved by introducing substituent acceptors with different extent of electronic delocalization and electron-withdrawing intensity into the poly(triphenylamine)s. The highly fluorescent CN-PTPA exhibited volatile DRAM memory characteristic due to the large band gap and weak intramolecular charge transfer capability. 2CN-PTPA and 3CN-PTPA showed volatile SRAM memory property with retention time of 5 and 14 min, respectively, depending on electron-withdrawing capability of the acceptors. Furthermore, NO2-PTPA afforded nonvolatile WORM memory behavior attributed to the charge could be trapped into the nonconjugated nitro group even though the dipole moment and electron-withdrawing capability of nitro group were weaker than cyanovinyl groups. Moreover, except NO2-PTPA, all the devices derived from cyano-containing ambipolar polymers including CN-PTPA, 2CN-PTPA, and 3CN-PTPA could be switched to the ON state and exhibited WORM memory behavior in positive unipolar I-V switching. This phenomenon indicated that the Al atoms preferentially interact with poly(triphneylamine)s containing cyano than nitro substituents.

Facile anionic synthesis of a well-controlled thermally cross-linkable block copolymer for polymer-based resistive memory device applications

A well-defined block copolymer containing a thermally cross-linkable ethynyl group has been synthesized by living anionic polymerization for polymer-based resistive memory device applications.

Synthesis of imidazole derivatives and study of the ON-based different memory performances

We report the synthesis of two imidazole-based small molecules with different planarity of terminal aromatic rings and their application in memory devices with a sandwich configuration. The optical, electric, and the on-based device performances were systematically investigated. Surprisingly, the device based on BT-PMZ exhibited volatile static random access memory (SRAM) behavior, whereas that based on BT-BMZ showed nonvolatile write-once-read-many-times (WORM) behavior. Further studies on the film morphology and the molecular electronic structure were carried out to investigate the underlying mechanism for the large difference in their performance. Moreover, the performance of the device that incorporates a LiF buffer layer (5 nm) embedded at the interface between the BT-BMZ active layer and the Al top electrode as well as that of the device with a cold-deposited top electrode of mercury droplet was further investigated. At that point a dramatic change in memory performance of the devices from the WORM to SRAM type was observed. The intrinsic volatile SRAM performance for the two molecules results from the moderate electron-withdrawing strength of the acceptor moieties and thus weak trapping of the charge carriers.

Adjustment of ON-state retention ability based on new donor-acceptor imides through structural tailoring for volatile device applications

In this study, two D-A molecules NACANA and CANACA, based on carbazole (CA) donor and naphthalimide (NA) acceptor, with different D-A arrangement (A-D-A and D-A-D) were synthesized. The photophysical and electrochemical properties, microstructure and memory behaviors of both A-D-A and D-A-D molecules were systematically investigated. The fabricated devices ITO/NACANA or CANACA layer/Al with a simple sandwich configuration both exhibited volatile nature after shutting off the external electric field. Interestingly, NACANA showed ON-state retention time of ca. 12 min, longer than that of CANACA (ca. 6 min). The difference in retention ability of the programmed states could be assigned to the difference of the D-A arrangement. This type of retention ability adjustment by varying the arrangement of donor and acceptor segments may provide a guide of structure design for future organic-based specific memory devices with tunable volatile property.

Polymer-based resistive memory materials and devices

Due to the advantages of good scalability, flexibility, low cost, ease of processing, 3D-stacking capability, and large capacity for data storage, polymer-based resistive memories have been a promising alternative or supplementary devices to conventional inorganic semiconductor-based memory technology, and attracted significant scientific interest as a new and promising research field. In this review, we first introduced the general characteristics of the device structures and fabrication, memory effects, switching mechanisms, and effects of electrodes on memory properties associated with polymer-based resistive memory devices. Subsequently, the research progress concerning the use of single polymers or polymer composites as active materials for resistive memory devices has been summarized and discussed. In particular, we consider a rational approach to their design and discuss how to realize the excellent memory devices and understand the memory mechanisms. Finally, the current challenges and several possible future research directions in this field have also been discussed.

Tunable electrical memory characteristics using polyimide:polycyclic aromatic compound blends on flexible substrates

Resistance switching memory devices with the configuration of poly(ethylene naphthalate)(PEN)/Al/polyimide (PI) blend/Al are reported. The active layers of the PI blend films were prepared from different compositions of poly[4,4'-diamino-4″-methyltriphenylamine-hexafluoroisopropylidenediphthalimide] (PI(AMTPA)) and polycyclic aromatic compounds (coronene or N,N-bis[4-(2-octyldodecyloxy)phenyl]-3,4,9,10-perylenetetracarboxylic diimide (PDI-DO)). The additives of large π-conjugated polycyclic compounds can stabilize the charge transfer complex induced by the applied electric field. Thus, the memory device characteristic changes from the volatile to nonvolatile behavior of flash and write-once-read-many times (WORM) as the additive contents increase in both blend systems. The main differences between these two blend systems are the threshold voltage values and the additive content to change the memory behavior. Due to the stronger accepting ability and higher electron affinity of PDI-DO than those of coronene, the PI(AMTPA):PDI-DO blend based memory devices show a smaller threshold voltage and change the memory behavior in a smaller additive content. Besides, the memory devices fabricated on a flexible PEN substrate exhibit an excellent durability upon the bending conditions. These tunable memory performances of the developed PI/polycyclic aromatic compound blends are advantageous for future advanced memory device applications.

Improving the characteristics of an organic nano floating gate memory by a self-assembled monolayer

We demonstrate a novel approach to improve the characteristics of the gold nanoparticle-based organic transistor memory devices by using self-assembled monolayers (SAM) with different functional groups as interfacial modifier. SAM-based interfacial engineering significantly improved the hysteresis, memory window, and on/off ratio of a nano floating gate memory (NFGM) at zero gate voltage. This NFGM showed a large memory window of up to 190 V and on/off current ratio of 10(5) during writing and erasing with an operation voltage of 100 V of gate bias in a short time, less than 1 s. Furthermore, the devices show excellent nonvolatile behavior for bistable switching. The ON and OFF state can be stably maintained for 10(3) s with an I(on)/I(off) current ratio of 10(6) for a pentafluorophenyl trimethoxysilane modified device. The results suggested the importance of SAM-modified interface for the memory performance of NFGMs.

Single polymer-based ternary electronic memory material and device

A ternary polymer memory device based on a single polymer with on-chain Ir(III) complexes is fabricated by combining multiple memory mechanisms into one system. Excellent ternary memory performances-low reading, writing, and erasing voltages and good stability for all three states-are achieved.