Aromatic Polyimines Research Articles

SYNTHESIS AND PROPERTIES OF POLYIMINES BASED ON DIALDEHYDES OF THE FURAN SERIES AND VARIOUS DIAMINES

In this work, the reactions of 2,5-diformylfuran (DFF) with various aromatic and aliphatic diamines were studied, and the physicochemical properties of the resulting polyimines were studied. Research on the synthesis of electro-conductive polymers and the study of their physicochemical properties attracts great interest in modern polymer science. A class of electrically conductive polymers that has been particularly attractive for research in the last half century are aromatic polyimines, which are also known as polyimines or Schiff-based polymers. DFF-based polymers are little studied due to the high cost of the monomer, which limits its synthetic application. The availability of DFF is made both by the development of economical methods for its production, the oxidation of 5-hydroxymethylfurfural (5-HMF), and by the provision of sustainable access to 5-HMF from biomass. Polyimines containing furan fragments were synthesized by low-temperature polycondensation of DFF, available from plant materials, and various aromatic diamines in ethanol. The resulting polymers were high-melting thermoplastics from yellow to orange. The polymers showed typical absorption bands characteristic of the stretching vibrations of the C=N group (about 1620 cm-1) in the infrared spectra and had high glass transition temperatures of more than 200 °C. The ionic conductivity of polyimines has been characterized by electrochemical impedance spectroscopy. The conductivity value for polyimines, doped with I2, reaches 1.24·10-4 S cm-1 (at 298 K and 100% relative humidity), which is one of the highest values of proton conductivity for polyimines doped without using metals or their salts. The resulting polymers can be used to manufacture composites with various fillers. For citation: Kataria Y.V., Klushin V.A., Kashparova V.P., Sokolova V.A., Smirnova N.V. Synthesis and properties of polyimines based on dialdehydes of the furan series and various diamines. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 6-12. DOI: 10.6060/ivkkt.20236606.6763.

Aromatic polyimine covalent adaptable networks with superior water and heat resistances

Polyimine covalent adaptable networks (CANs) exhibit several dynamic characteristics (such as recyclability and reprocessability) that are beneficial for compensating for the disadvantages of traditional petroleum-based synthetic thermosetting resins, and are therefore suggested as potential substitutes for environmentally unfriendly resins. However, owing to the lack of sufficient stability of imine bonds and their linked molecular chains, most polyimine CANs do not exhibit superior properties in applications with high stability requirements, such as strong water resistance, high heat resistance, and excellent mechanical strength. In this study, we designed and synthesized a new class of aromatic petroleum-based polyimine CANs to improve the stability of imine bonds and molecular chains employing the conjugation effect of the two benzene rings to C=N and aromatic structures. In contrast, these CANs simultaneously demonstrate superior water resistance (water absorption: 0.14–0.15%) and heat resistance (5% weight loss (Td5%): 434–441 °C; glass transition temperature (Tg): 217–239 °C) than that of previously reported polyimine CANs (water absorption: 0.90–90%; Td5%: 200–348 °C; Tg: 47–215 °C). They have outstanding mechanical properties that are almost unaffected by adsorbed water. Meanwhile, the resins exhibited remarkable resistance to ordinary acids, bases, oxidants, salts, solvents, and oils, except for several special solvents. In addition, like other polyimine CANs, they maintain their dynamic behavior characteristics, including degradability, recyclability, malleability, reprocessability, and rehealability. This study provides a new method to improve the comprehensive performance of polyimine CANs through reasonable molecular structure design.

Cobalt-Doped Carbon Nitride Frameworks Obtained from Calcined Aromatic Polyimines as Cathode Catalyst of Anion Exchange Membrane Fuel Cells.

Cobalt-doped carbon nitride frameworks (CoNC) were prepared from the calcination of Co-chelated aromatic polyimines (APIM) synthesized from stepwise polymerization of p-phenylene diamine (PDA) and o-phthalaldehyde (OPAl) via Schiff base reactions in the presence of cobalt (II) chloride. The Co-chelated APIM (Co-APIM) precursor converted to CoNC after calcination in two-step heating with the second step performed at 100 °C lower than the first one. The CoNCs demonstrated that its Co, N-co-doped carbonaceous framework contained both graphene and carbon nanotube, as characterized by X-ray diffraction pattern, Raman spectra, and TEM micropictures. CoNCs also revealed a significant ORR peak in the current–voltage polarization cycle and a higher O2 reduction current than that of commercial Pt/C in a linear scanning voltage test in O2-saturated KOH(aq). The calculated e-transferred number even reaches 3.94 in KOH(aq) for the CoNC1000A900 cathode catalyst, which has the highest BET surface area of 393.94 m2 g−1. Single cells of anion exchange membrane fuel cells (AEMFCs) are fabricated using different CoNCs as the cathode catalysts, and CoNC1000A900 demonstrates a peak power density of 374.3 compared to the 334.7 mW cm−2 obtained from the single cell using Pt/C as the cathode catalyst.

Fully Aromatic Polyimine Covalent Adaptable Networks with Superior Water and Heat Resistances

Fully Aromatic Polyimine Covalent Adaptable Networks with Superior Water and Heat Resistances

Fe, N-Doped Metal Organic Framework Prepared by the Calcination of Iron Chelated Polyimines as the Cathode-Catalyst of Proton Exchange Membrane Fuel Cells.

Aromatic polyimine (PIM) was prepared through condensation polymerization between p-phenylene diamine and terephthalaldehyde via Schiff reactions. PIM can be physically crosslinked with ferrous ions into gel. The gel-composites, calcined at two consecutive stages, with temperatures ranging from 600 to 1000 °C, became Fe- and N-doped carbonaceous organic frameworks (FeNC), which demonstrated both graphene- and carbon nanotube-like morphologies and behaved as an electron-conducting medium. After the two-stage calcination, one at 1000 °C in N2 and the other at 900 °C in a mixture of N2 and NH3, an FeNC composite (FeNC-1000A900) was obtained, which demonstrated a significant O2 reduction peak in its current–voltage curve in the O2 atmosphere, and thus, qualified as a catalyst for the oxygen reduction reaction. It also produced a higher reduction current than that of commercial Pt/C in a linear scanning voltage test, and the calculated e-transferred number reached 3.85. The max. power density reached 400 mW·cm−2 for the single cell using FeNC-1000A900 as the cathode catalyst, which was superior to other FeNC catalysts that were calcined at lower temperatures. The FeNC demonstrated only 10% loss of the reduction current at 1600 rpm after 1000 redox cycles, as compared to be 25% loss for the commercial Pt/C catalyst in the durability test.

Synthesis, Characterization, Electrical Conductivity and Fluorescence Properties of Polyimine Bearing Phenylacetylene Units.

In this study, a Schiff base was synthesized by the condensation reaction of 4-bromobenzaldehyde and 4-aminophenol. Then, phenylacetylene substituted Schiff base monomer (IPA) was obtained by HBr elimination reaction of IPA with phenylacetylene through Sonogashira reaction. IPA was polymerized via chemical oxidative polycondensation reaction. FT-IR and NMR measurements were used for the structural analyses of the synthesized substances. Fluorescence and UV-Vis analyses were carried out for optical characterization. Electrochemical characteristics, electrical conductivities and thermal properties were determined using cyclic voltammetry (CV), four-point probe conductometer, TG-DTA and DSC methods. The main purpose of the present study was to investigate the effects of phenylacetylene bearing units on the properties of conjugated aromatic polyimines. The spectral analysis signified a green light emission behavior when irradiated at different wavelengths. Combined with fluorescent behavior and good thermal stability, the electrical conductivity was found to be very crucial for π-conjugated polymer.

Synthesis and characterization of conjugated polyphenols derived from azomethine formation containing terephtaldehyde via oxidative polycondensation

ABSTRACTPreparation of conjugated aromatic polyimines, containing phenols in the backbone and side group substitutions, has been successfully achieved by a chemical oxidative polycondensation of a series of Schiff bases using NaOCl as the oxidant at optimum reaction temperature of 90°C. The molecular structures of synthesized compounds were verified by the FT-IR, UV-Vis, 1H-NMR and 13C-NMR techniques. Using thermogravimetric analysis-differential thermal analysis (TG-DTA) and size exclusion chromatography (SEC), the molecular weight distribution parameters and the characterization of all compounds could be specified. The initial degradation temperatures of the polymers were found in the range of 170–271°C. DSC analyses of the polyazomethines (PAMs) were carried out to assign the glass transition temperatures (Tg). UV-Vis measurements gave information about the optical (Eg) band gaps. Fluorescence measurements were carried out to obtain the maximum PL intensities. The spectral analysis outcome signified a blue and a green light emission behavior when irradiated at different wavelengths. Cyclic Voltammetry (CV) was an effective method to explore the HOMO and LUMO energy levels and electrochemical () band gaps of the polymers. The HOMO energy levels of the synthesized polyimines were lower than those of the monomers indicating the more conjugated structures of the polymers. Four-point collinear probe was used to determine the electrical conductivities of both doped and undoped states of the synthesized polymers with respect to doping time with iodine. The morphological properties of the polymers were illustrated using Scanning Electron Microscopy (SEM) images at different amplifications.

Synthesis of a Two-Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface.

A two-dimensional covalent organic monolayer was synthesized from simple aromatic triamine and dialdehyde building blocks by dynamic imine chemistry at the air/water interface (Langmuir-Blodgett method). The obtained monolayer was characterized by optical microscopy, scanning electron microscopy, and atomic force microscopy, which unambiguously confirmed the formation of a large (millimeter range), unimolecularly thin aromatic polyimine sheet. The imine-linked chemical structure of the obtained monolayer was characterized by tip-enhanced Raman spectroscopy, and the peak assignment was supported by spectra simulated by density functional theory. Given the modular nature and broad substrate scope of imine formation, the work reported herein opens up many new possibilities for the synthesis of customizable 2D polymers and systematic studies of their structure-property relationships.

Synthesis of a Two‐Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface

AbstractA two‐dimensional covalent organic monolayer was synthesized from simple aromatic triamine and dialdehyde building blocks by dynamic imine chemistry at the air/water interface (Langmuir–Blodgett method). The obtained monolayer was characterized by optical microscopy, scanning electron microscopy, and atomic force microscopy, which unambiguously confirmed the formation of a large (millimeter range), unimolecularly thin aromatic polyimine sheet. The imine‐linked chemical structure of the obtained monolayer was characterized by tip‐enhanced Raman spectroscopy, and the peak assignment was supported by spectra simulated by density functional theory. Given the modular nature and broad substrate scope of imine formation, the work reported herein opens up many new possibilities for the synthesis of customizable 2D polymers and systematic studies of their structure–property relationships.

FTIR studies on protonation of selected aromatic polyimines

Protonation of selected aromatic polyazomethines by methanesulfonic acid and p-chlorophenol were investigated using FTIR spectroscopy. The influence of the protonation agent on the conjugation effect in polymers is discussed. To explain the observed differences in the protonation effects, geometry optimization was performed for systems of model compounds and protonation agents. For the model compounds the appropriate bis-Schiff bases consisting of two imine groups placed between three phenyl rings were used for calculations.

ChemInform Abstract: Towards Molecular Electronics: A New Family of Aromatic Polyimines Chelates Substituted with Alkynes Groups.

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Poly(arylene amine)s from the Reduction of Aromatic Polyimines

Poly(arylene amine)s were prepared from the reduction of aromatic poly(anthraquinone imines), which are readily available from the condensation reaction of arylene diamines and anthraquinones or 2,5-dimethylbenzoquinone. The reduction reaction was studied in detail with model diimines derived from anthraquinones. Simply stirring in hydrazine monohydrate at 70 °C readily reduced a polyimine derived from 2,5-dimethylbenzoquinone. Complete reduction of the polymers derived from anthraquinone or its derivatives was achieved by using hydrazine monohydrate in the presence of a palladium catalyst at 65 °C. These polymers have potential useful properties as photoconductors or antioxidants and extend the series of polyaniline analogues under very controlled structural and synthetic conditions.

Probing Structure−Property Relationships in Third-Order Nonlinear Optical Polymers: Third Harmonic Generation Spectroscopy and Theoretical Modeling of Systematically Derivatized Conjugated Aromatic Polyimines

Picosecond third harmonic generation (THG) spectroscopy in the range 0.9−2.4 μm (0.52−1.38 eV) and sum-over-states (SOS) theoretical modeling have been used to investigate the third-order nonlinear optical properties of a series of nine conjugated aromatic polyimines designed to elucidate structure−χ(3) relationships in conjugated polymers. The THG-measured frequency-dispersed third-order susceptibility (χ(3)) of the series of polymers has off-resonant and three-photon resonance-enhanced values in the ranges of 1.1 × 10-12 to 2.0 × 10-11 and 6.4 × 10-12 to 7.2 × 10-11 esu, respectively, demonstrating a large modulation of nonlinear optical response by simple structural variations. A random copolymer was found to have enhanced χ(3) compared to either of its parent homopolymers. Asymmetric donor side-group substitutions were found to result in 7−10-fold enhancement of off-resonant χ(3) compared to either symmetric substitutions or no substitutions. Theoretical three- and four-level SOS models, justified by ...

Synthesis and self-assembled multilayer thin film formation of water-soluble conjugated aromatic polyimines

Synthesis and self-assembled multilayer thin film formation of water-soluble conjugated aromatic polyimines

Synthesis and self-assembled multilayer thin film formation of water-soluble conjugated aromatic polyimines

Abstract : A new series of water soluble conjugated aromatic polyimines containing sulfonate groups have been synthesized via polycondensation reaction between diamines and dialdehydes at room temperature. The polymers are soluble in water and N, N-diamethylformamide (DMF), giving colored solutions with absorption maxima (gammamax) ranging from 400 to 480nm. One of the polyimines (PIP) showed strong fluorescence in aqueous solution and concentration dependence of photo luminescence has been investigated. Electrostatic self assembly of multilayer films consisting of each polyimine as a polyanion and poly(diallyldimethylammonium chloride) as a polycation was successfully carried out by alternate deposition in corresponding aqueous solutions.

Synthesis and self-assembled multilayer thin film formation of water-soluble conjugated aromatic polyimines

A new series of water-soluble conjugated aromatic polyimines containing sulfonate groups have been synthesized via polycondensation reaction between diamines and dialdehydes at room temperature. The polymers are soluble in water and N,N-dimethylformamide, giving colored solutions with absorption maxima (λmax) ranging from 400 to 480 nm. One of the polyimines (PIP) showed strong fluorescence in aqueous solution, and concentration dependence of photoluminescence has been investigated. Electrostatic self-assembly of multilayer films consisting of each polyimine as a polyanion and poly(diallyldimethylammonium chloride) as a polycation was successfully carried out by alternate deposition in corresponding aqueous solutions.

Heteropolyanions doped polyimine—Preparation and spectroscopic properties

It is demonstrated that aromatic polyimine obtained by the condensation of p-phenylenediamine and terephtalaldehyde can be chemically doped with heteropolyanions of Keggin-type. The spectroscopic studies show that polyimine undergoes protonation. The structural identity of the Keggin units are preserved upon incorporation into the polymer matrix.

Conjugated Aromatic Polyimines. 2. Synthesis, Structure, and Properties of New Aromatic Polyazomethines

Abstract : A series of 20 conjugated aromatic Polyimines, containing p-phenylene, p-biphenylene, p-terphenylene, 4,4'- stilbene, and 1,5-naphthalene linkages in the backbone and various electron-donating and electron-withdrawing side-group substitutions, have been synthesized, characterized, and used to investigate the effects of molecular structure on the electronic structure and properties of conjugated polymers. Soluble gallium trichloride or diarylphosphate complexes of the aromatic polyimines in organic solvents facilitated their solution spectroscopic characterization and their processing into thin film and coatings. Electrochemical reduction of the aromatic polyimines was reversible with formal potential of -1.93 to -1.52 V (SCE) and 0.22 to 0.86 charge transferred whereas oxidation was irreversible. The electron affinity and ionization potentials of the series of polymers varied from 2.46 to 2.94 eV and from 4.80 to 5.38 eV, respectively. The associated LUMO and HOMO energy levels are thus tunable by up to 0.48 eV and 0.58 eV, respectively. The electrochemically and optically determined LUMO-HOMO energy gaps of thin films were very close and in the range of 2.08-2.77 eV. The results of this study show that aromatic polyimines are an interesting class of pi-conjugated polymers whose structure and properties can be regulated over a wide range by variation in backbone structure, side group substitution, and through intramolecular hydrogen bonding or complexation, backbone planarity. jg

Towards molecular electronics: a new family of aromatic polyimine chelates substituted with alkyne groups

Bromo and chloro polyimines react with trimethylsilyacetylene in the presence of Pd(PPh 3) 2Cl 2/CuI and diisopropylamine to give new substituted polyimines 1a to 8a. These compounds are deprotected with K 2CO 3 in MeOH / THF to produce the corresponding terminal alkynes 1b to 8b.

ChemInform Abstract: A New Family of Aromatic Polyimine Chelates Substituted with Two Diphenylphosphines.

Abstract2,7‐Dichloronaphthyridine (I) reacts with lithium diphenylphosphide (II) to yield the bis(diphenylphosphino)naphthyridine (III).