Synthesis and memory characteristics of polyimides containing noncoplanar aryl pendant groups

Synthesis and memory properties of a series of novel asymmetric soluble polyimides

Two asymmetric diamines [1,1′-biphenyl]-4-yl(3,5-diaminophenyl) methanone (BPDAM) and (3,5-diaminophenyl)(4′-(naphthalen-1-yl)-[1,1′-biphenyl]-4-yl) methanone(DANPBPM) were synthesized by Suzuki coupling reaction from (4-bromophenyl)(3,5-diaminophenyl) methanone (BDAM) and corresponding arylboronic acid. A series of polyimides exhibiting organic solubility were prepared from 2,2′,3,3′-biphenyl tetracarboxylic dianhydride(BPDA) and these above three new diamines via a two-stage process. The obtained polymers showed outstanding organic solubility and high thermal stability. And studies have shown that the storage device with a sandwich type configuration of Al/polyimide/ITO was prepared by the traditional liquid spin coating technology, which showed the storage capacity of flash memory type. All the polyimide-based devices showed bistable conductivity switching and nonvolatile memory behavior that had long preservation period and high ON/OFF electric current, the rate of which was 104.

The effects of long and bulky aromatic pendent groups with flexible linkages on the thermal, mechanical and electrical properties of the polyimides and their nanocomposites with functionalized silica

A novel diamine bis(4-aminophenyl)bis{3,4[(4-(8-quinolyloxymethyl carbonyl)]}methane, containing two long/bulky aromatic pendent chains was synthesized by incorporating aromatic and hetero aromatic groups with flexible linkages. Flexible, stretchable, thermally stable and processable polyimides were prepared by reacting this newly synthesized diamine with commercial tetracarboxylic acid dianhydrides like 3,3',4,4'-benzophenone tetra carboxylic acid dianhydride (BTDA) and 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic Anhydride (BPADA). Nanocomposites of polyimides were prepared using aromatic amine functionalized silica as a filler by solution casting method. The current work investigates the effects of incorporating long/bulky aromatic side chains and flexible linkages on the thermal, mechanical, electrical and optical properties of the polyimides and nanocomposites. The polyimides showed good thermal stability (T 10% = 364 & 388), high flame resistance, low glass transition temperatures (T g = 130 °C & 156 °C), very low dielectric constants (2.5 & 2.8 at 1 MHz) and good optical transparency. The neat polyimides displayed good elongation at break (133-155%) but possessed low tensile strength. The chemically imidized polyimides showed good solubility in low and high boiling solvents. Nanocomposites of polyimides based on aromatic amine functionalized silica exhibited enhanced properties with T 10% values varying between 409-482 °C, T g between 165-280 °C and higher dielectric constants (3-5.7 at 1 MHz).

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.

(Z)-1,2-Bis(3-bromophenyl)diazene 1-oxide

The title compound C12H8Br2N2O, lies on an inversion centre in the space group P21/n. Doubts are cast on the report of a polymorph of this structure in the non-centrosymmetric space group P21 [Zhu, R.-T., Liu, J.-C., Jin, S., Liu, B. & Guo J.-P. (2006). Hecheng Huaxue (Chin. J. Synth. Chem.) 14, 591] as ADDSYM alerts point strongly to a centrosymmetric structure. In the crystal, C—H...O and C—H...Br hydrogen bonds together with offset π–π interactions stack the molecules along the a-axis direction.

Synthesis and non-volatile electrical memory characteristics of triphenylamine-based polyimides with flexibility segments

Two triphenylamine-based polyimides (PI(TPA-PMDA) and PI(TPA-BPDA)) containing a flexibility segments were prepared. The memory device of ITO/PI(TPA-PMDA)/Al exhibited write-once read-many-times (WORM) memory behavior, however, the memory device of PI(TPA-BPDA) demonstrated flash-type memory characteristics.

Synthesis and optical and electrochemical memory properties of fluorene–triphenylamine alternating copolymer

A fluorene–triphenylamine copolymer (PF–TPA) was designed and synthesized under Suzuki coupling reaction conditions in this work. It exhibited a typical electrical conductance switching behavior and non-volatile flash memory effects.

Novel solution-processable functional polyimide/ZrO2 hybrids with tunable digital memory behaviors

The resulting PI hybrid films exhibited electrically programmable digital memory properties from DRAM, SRAM to WORM with a high ON/OFF current ratio by controlling the content of ZrO₂ from 0 to 30 wt%.

Electrically bistable and non-volatile memory devices based on p-toluenesulfonic-doped poly(triphenylamine)

The devices are bi-directionally switchable and have non-volatile WORM memory characteristics. They were used as promising candidates in security and data protection applications.

Synthesis of soluble polyimides based on ether-linked cyclohexyldiamine and their ultraviolet shielding behavior

A series of polyimides (PIs) based on ether-linked cyclohexyldiamine were prepared using pyromellitic dianhydride (PI-1), benzophenone dianhydride (PI-2), naphthalene dianhydride (PI-3), and perylene dianhydride (PI-4) in 1-methyl-2-pyrrolidone (NMP) medium to obtain respective polyamic acids and are subsequently converted into PIs through thermal imidization. The resulting PIs were characterized by Fourier transform infrared, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and impedance analyses. In addition, the ultraviolet (UV) shielding ability of PIs was also studied and discussed. The vibrational analysis confirms the imidization, and the XRD profile indicates the amorphous nature of the resulting PIs. The PIs synthesized in the present work exhibit good solubility in organic solvents such as NMP, dimethylformamide (DMF), and dimethyl sulfoxide (DMSO). The PI-4-based imide possesses very good solubility with the highest glass transition temperature value of 256°C, highest char yield of 50.16%, highest dielectric constant of 3.9 and higher UV shielding performance of 89% than those of other PIs. Further, the good solubility also makes them useful for coating applications in aerospace and liquid crystal displays.

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.