High Performance Volatile Polymeric Memory Devices Based on Novel Triphenylamine-based Polyimides Containing Mono- or Dual-Mediated Phenoxy Linkages

Effect of terminal substituent of iso-indigo-based materials on the intermolecular stacking and memory performance

Attributed to the characteristics of narrow band gap structural units and full spectral response, iso-indigo is often used as an electron acceptor in organic electronic materials. Organic molecules with large conjugated surfaces and strong intermolecular forces can form ordered stacked structures through self-assembly. In this paper, the self-assembly performances of IDCF3 and IDCN are regulated by changing the end groups. The effects of terminal groups on the resistive memory behaviours and reproducibility are investigated. The properties of IDCF3 and IDCN devices are characterized by UV-VIS spectroscopy, cyclic voltammetry and DSC diffraction. The results show that when the end groups with different steric hindrance are introduced into the ends of the molecules with good backbone plane, the conjugated surfaces of the molecules will bend due to the different steric hindrance of the end groups in the form of cambium and layer-ordered packing, which will affect the threshold voltage and device reproducibility.

Tailoring the Resistive Switching WORM Memory Behavior of Functionalized Bis(triphenylamine)

To better understand the structure-property relationship and the significance of the donor-acceptor (D-A) system in resistive memory devices, a series of new organic small molecules with A-π-D-π-A- and D-π-D-π-D-based architecture comprising a bis(triphenylamine) core unit and ethynyl-linked electron donor/acceptor arms were designed and synthesized. The devices with A-π-D-π-A structures exhibited write-once-read-many memory behavior with a good retention time of 1000 s while those based on D-π-D-π-D molecules presented only conductor property. The compound with nitrophenyl substitution resulted in a higher ON/OFF current ratio of 10⁴, and the fluorophenyl substitution exhibited the lowest threshold voltage of -1.19 V. Solubility of the compounds in common organic solvents suggests that they are promising candidates for economic solution-processable techniques. Density functional theory calculations were used to envision the frontier molecular orbitals and to support the proposed resistive switching mechanisms. It is inferred that the presence of donor/acceptor substituents has a significant impact on the highest occupied molecular orbital-lowest unoccupied molecular orbital energy levels of the molecules, which affects their memory-switching behavior and thus suggests that a D-A architecture is ideal for memory device resistance switching characteristics.

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

Three novel polyimides (PI(TPF-Br BPDA), PI(TPF-Ph BPDA), and PI(TPF-Ph-OMe BPDA)) with tetraphenyl fluorene (TPF) were synthesized and tested. The laboratorial results showed that the constructed electronic devices exhibited different memory behaviors due to the different steric hindrance substituents (bromine atom, phenyl, and 3,5-dimethoxyphenyl) in 2,7-position of TPF molecule. The memorizers based on PI(TPF-Br BPDA) and PI(TPF-Ph BPDA) presented volatile dynamic random access memory (DRAM) feature with turn-on voltages of −2.39 and +1.45 V, as same as −1.71 and +1.74 V, separately. However, the PI(TPF-Ph-OMe BPDA) based apparatus exhibited non-volatile write-once read-many-times memory (WORM) behavior with turn-on voltage of −1.13 V, due to the more charge traps of 3,5-dimethoxyphenyl moieties and higher dipole moment. The switching mechanism was verified by quantum simulation of energy level, electrostatic potential (ESP) surface and dipole moment. These results indicated that the electrical memory performance of the synthesized TPF-based PIs could be adjusted by modifying the electron donor structure.

Preparation and properties of polyimide-based nanocomposites containing functionalized Fe3O4 nanoparticles

Polyimide (PI)/Fe3O4 nanocomposites were successfully prepared via the thermal curing of different amounts of Fe3O4 nanoparticles (2, 4, 6 and 8 wt%) functionalized by 3-aminopropyltriethoxy silane as a coupling agent, containing the poly(amic acid) derived from 5-diamino- N-(4-(4,5-diphenyl-1H-imidazol)phenyl)benzamide and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride. The effect of Fe3O4 nanoparticles on the structural, thermal and magnetic properties of nanocomposites was investigated. The Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) results reveal that the surface of Fe3O4 nanoparticles is sufficiently compatible with PI through linkage of the coupling agent between Fe3O4 and the polymer. Also, the SEM image shows that Fe3O4 nanoparticles are dispersed uniformly in the polymer matrix, with a particle size of around 78 nm. The nanocomposites of 2 and 8 wt% exhibit the saturation magnetization values of 0.055 and 0.170 emu g− 1, respectively. The thermogravimetric analysis data show that the thermal stability of the nanocomposites is improved as compared to the pure PI.

Investigation of thermal and fluorescent properties of benzoxazole-linked triphenylamine-based co-polyimides

A series of novel fluorescent co-polyimides are obtained by combining N 1-(4-aminophenyl)- N 1-(4-(benzo[ d]oxazol-2-yl) phenyl) benzene-1,4-diamine and 4,4′-oxydianiline with four aromatic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 4,4′-oxydiphthalic anhydride, and 4,4 ′-(hexafluoroisopropylidene)diphthalic anhydride following conventional polycondensation method. The resultant co-polyimides are characterized by elemental, Fourier transform infrared spectral analysis and gel permeation chromatography. All newly prepared polyimides (PIs) exhibit shallow highest occupied molecular orbital energy levels in the range of −4.47 to −4.98 eV and have reasonable optical bandgaps. The photoluminescence spectral analysis shows blue to green emission in solution form. Thermal and solubility properties reveal that the PIs with pendant 4-(benzo[ d]oxazol-2-yl group linked to triphenylamine unit in polymer backbone impart not only good thermal stability but also appreciable solubility making these new co-polyimides versatile for multipurpose usage.

Theoretical Study of Electrochemical and Electrochromic Properties of Novel Viologen Derivatives: Effects of Donors and π-Conjugation

We propose a linkage approach by merging ambipolar electrochromic (EC) materials in both π-acceptor-π (π-A-π) and donor-acceptor-donor (D-A-D) configurations and investigated their electrochemical and spectroelectrochemical properties using density functional theory calculations. Here, we considered anthracene, toluene, and pyrene as π-conjugated molecules, triphenylamine (TPA) as a donor, and viologen as an acceptor moiety for π-A-π and D-A-D configurations. We have also explored the substitutional effects in the donor moiety on the overall electrochromism during both oxidation and reduction processes. Here, we mainly focused on the relationship between the structure, substitution of functional groups, electronic and spectral properties, as well as redox potential of the designed monomers. Our calculations indicate that the designed monomers have attractive absorption properties and show clear color switching upon the redox process. We find that the substitution of stronger electron-donating and π-spacer groups create new absorption peaks in the oxidation states. These designed viologen derivatives will be potential candidates, which can be used in both oxidation and reduction processes for upcoming EC devices.

Covalent Organic Nanosheets as Effective Sodium-Ion Storage Materials

Herein, we study the structure-dependent energy storage performance of network polymers (covalent organic nanosheets, CONs) prepared by Stille cross-coupling under conventional reflux and solvothermal conditions, showing that the specific surface area and self-assembled morphology of CONs could be effectively controlled by a careful choice of the synthetic route and monomer combination. The Na-ion storage capacity of the above nanosheets could be increased by enhancing their charge-carrier conductivity via enforcement of polymer backbone planarity or by increasing their specific surface area while maintaining backbone constitution. Comparison of anodes fabricated using six CONs showed that the electrode based on CON-16 exhibited the best cycling performance and rate capability, retaining a reversible discharge capacity of ∼250 mA h/g after 30 cycles at a current density of 100 mA/g.

Electrochemical Oxidative C-H Amination of Phenols: Access to Triarylamine Derivatives

Dehydrogenative C-H/N-H cross-coupling serves as one of the most straightforward and atom-economical approaches for C-N bond formation. In this work, an electrochemical reaction protocol has been developed for the oxidative C-H amination of unprotected phenols under undivided electrolytic conditions. Neither metal catalysts nor chemical oxidants are needed to facilitate the dehydrogenation process. A series of triarylamine derivatives could be obtained with good functional-group tolerance. The electrolysis is scalable and can be performed at ambient conditions.

Highly efficient polymerization via sulfur(vi)-fluoride exchange (SuFEx): novel polysulfates bearing a pyrazoline–naphthylamide conjugated moiety and their electrical memory performance

Two polysulfates (PolyTPP-NI and CPTPP-NI) were synthesized by a SuFEx click reaction, and their memory devices show Flash behaviors.

Intrinsically stretchable, solution-processable functional poly(siloxane-imide)s for stretchable resistive memory applications

A stretchable WORM-type resistive memory device was fabricated using poly(siloxane-imide) ODPA-A12 with favorable mechanical properties.

Synthesis, Characterization and Application of Four Novel Electrochromic Materials Employing Nitrotriphenylamine Unit as the Acceptor and Different Thiophene Derivatives as the Donor

In this study, four novel donor⁻acceptor systems, 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin -5-yl)-N-(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)phenyl)-N-(4-nitrophenyl)aniline (NETPA), 4- (4-methoxythiophen-2-yl)-N-(4-(4-methoxythiophen-2-yl)phenyl)-N-(4-nitrophenyl)aniline (NMOTPA), 4-(4-methylthiophen-2-yl)-N-(4-(4-methylthiophen-2-yl)phenyl)-N-(4-nitrophenyl) aniline (NMTPA) and 4-nitro-N,N-bis(4-(thiophen-2-yl)phenyl)aniline (NTTPA), were successfully synthesized by Stille coupling reaction and electropolymerized to obtain highly stable conducting polymers, PNETPA, PNMOTPA, PNMTPA and PNTTPA, respectively. The polymers were characterized using cyclic voltammetry (CV), step profiling and UV⁻Vis⁻NIR spectroscopy. The band gaps (Eg values) were 1.34, 1.59, 2.26, and 2.34 eV, for PNETPA, PNMOTPA, PNMTPA and PNTTPA, respectively. In addition, electrochromic switching showed that all polymers exhibit outstanding optical contrasts, high coloration efficiencies and fast switching speeds in the near-infrared region (NIR). These properties make the polymers suitable materials for electrochromic applications in NIR region.

Preparation and flash memory performance based on fluorene–triphenylamine copolymer (PF–TPA)/MWCNTs

A conjugated alternating polymer based on fluorene and triphenylamine (PF–TPA) was devised and synthesized on the basis of the Suzuki coupling method, in which triphenylamine (TPA) as electron donor and hole transporting group.

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

Three isomeric polyimides with exactly the same chemical components and altered spatial configuration possess vastly different memory behaviors.

A direct crossed polymerization of triphenylamines and cyclohexanones via CC bond formation: the method and its bioimaging application

Fluorescent polymers synthesized by ACC reactions with interesting optical performances and the potential cell imaging applications.

Direct synthesis of triphenylamine-containing polyarylsulfones from commercially available aniline

A novel triphenylamine-containing polyarylsulfone (PAS-TPA) was synthesized from commercially available aniline and 1,1′-sulfonylbis(4-fluorobenzene) via two-step N–C coupling reaction under nucleophilic substitution polycondensation condition. Subsequently, a new series of polysulfones with different TPA contents (PSU-TPAs) was developed by the same method. Both PAS-TPA and PSU-TPAs not only exhibited good thermal stability and solubility but also exhibited intense ultraviolet absorption and fluorescence and high fluorescence quantum yield (approximately 16–42%). Their ideal highest occupied molecular orbital level (approximately −5.5 to −5.6) indicated the potential application of these polymers in organic photoelectronic fields.

Synthesis and properties of electroactive aromatic polyimides with methyl- or trifluoromethyl-protecting triphenylamine units

Two series of new redox-active aromatic polyimides with methyl- (–CH3) or trifluoromethyl (–CF3)-protecting triphenylamine moieties were prepared from 4,4′-diamino-4″-methyltriphenylamine and 4,4′-diamino-4″-(trifluoromethyl)triphenylamine with aromatic tetracarboxylic dianhydrides via the conventional two-step polycondensation technique. Flexible and strong polyimide films could be obtained via the thermal curing of their precursor poly(amic acid) films or direct solution cast from some organosoluble polyimides. The polyimides showed high glass-transition temperatures between 269°C and 312°C, and they did not show significant decomposition before 500°C in air or under nitrogen atmosphere. Cyclic voltammograms of the polyimide films on the indium–tin oxide-coated glass substrate exhibited a pair of reversible redox waves with half-wave oxidation potentials of 1.08–1.10 V (for the –CH3 series) and 1.23–1.26 V (vs. silver/silver chloride; for the –CF3 series) in acetonitrile solution. The polyimide films showed anodic electrochromism from pale yellow neutral state to purplish blue (for the –CH3 series) and chrome yellow (for the –CF3 series) when oxidized.

Synthesis and electrochemical properties of new redox-active polyimides with (1-piperidinyl)triphenylamine moieties

A series of new electroactive aromatic polyimides with (1-piperidinyl)triphenylamine moieties were prepared from 4,4′-diamino-4″-(1-piperidinyl)triphenylamine and aromatic tetracarboxylic dianhydrides via the conventional two-step polycondensation technique. Flexible and strong polyimide films could be obtained via the thermal curing of their precursor poly(amic acid) films. The polyimides showed high glass transition temperatures between 288°C and 318°C, and they did not show significant decomposition before 500°C in air or nitrogen atmosphere. Cyclic voltammograms of the polyimide films on the indium–tin oxide-coated glass substrate exhibited a pair of reversible oxidation waves with low onset oxidation potentials of 0.45–0.49 V (vs. silver/silver chloride) in acetonitrile solution. Upon oxidation, the color of the polyimide films changes from pale yellow to yellowish green and finally to blue.

Nonvolatile electrical switching behavior and mechanism of functional polyimides bearing a pyrrole unit: influence of different side groups

Influence of side groups to the nonvolatile electrical switching behaviors and its mechanism of polyimides bearing pyrrole unit were systematically studied.

Monodispersed ultramicroporous semi-cycloaliphatic polyimides for the highly efficient adsorption of CO2, H2and organic vapors

Monodispersed ultramicroporous semi-cycloaliphatic polyimides (sPIs) were synthesizedviasolution polycondensation and possess high uptakes for CO₂, H₂, aromatic and aliphatic vapors, exhibiting potential in gas storage and the recovery of toxic organic vapors.

Adjusting the Proportion of Electron-Withdrawing Groups in a Graft Functional Polymer for Multilevel Memory Performance

A polymer containing aldehyde active groups (PVB) was synthesized by atom transfer radical polymerization (ATRP), acting as a polymer precursor to graft a functional moiety via nucleophilic addition reaction. DHI (2-(1,5-dimethyl-hexyl)-6-hydrazino-benzo[de]isoquinoline-1,3-dione) and NPH (nitrophenyl hydrazine) groups, which contain naphthalimides that act as narrow traps and nitro groups that act as deep traps, were anchored onto the PVB at different ratios. A series of graft polymers were obtained and named PVB-DHI, PVB-DHI4 -NPH, PVB-DHI-NPH4 , and PVB-NPH. The chemical composition of the polymers was analyzed by (1) H-NMR spectroscopy and X-ray photoelectron spectroscopy (XPS). Memory devices were prepared from the polymers, and I-V characteristics were measured to determine the performance. By adjusting the ratio of different electron acceptors (DHI and NPH) to 4:1, ternary memory behavior was achieved. The relationship between memory behavior of PVB-DHIx NPHy and acceptor groups as well as their conduction mechanism were studied in detail.

High coloration efficiency and fast switching speed of poly(amic acid-imide)s containing triphenylamine in acidic electrolyte

The PAA-IM-1 film showed excellent reversible electrochromic stability and short switching time in acidic electrolyte (MBSA).