Azomethine Ether Research Articles

Poly(azomethine ether)‐derived carbon nanofibers for self‐standing and binder‐free supercapacitor electrode material applications

We report the microstructure and electrochemical performance of poly(azomethine ether) (PAME)‐derived carbon nanofibers (CNFs), which were fabricated by a facile two‐step process of electrospinning and carbonization, as self‐standing and binder‐free supercapacitor electrode materials. The SEM images showed that the average diameter decreased noticeably from ~293.9 nm of as‐spun nanofibers to ~150.3 nm of CNFs after the carbonization at 1000°C. The EDS, XPS, Raman, and XRD analyses demonstrated that PAME‐derived CNFs have a nitrogen self‐doped graphitic structure. Accordingly, PAME‐derived CNFs were characterized to have relatively high electrical conductivity of ~3.1 S/cm and excellent wettability to water. The cyclic voltammetry and galvanostatic charge/discharge tests revealed that PAME‐derived CNFs have a high specific capacitance of 298 F/g at 0.3 A/g, energy density of 3.3 to 13.9 Wh/kg, power density of 37.5 to 250.0 W/kg, and capacity retention of ~94% after 1000 cycles.

Microstructures and electrothermal characterization of aromatic poly(azomethine ether)‐derived carbon films

AbstractWe report the microstructural evolution and electrothermal properties of aromatic poly(azomethine ether) (PAME)‐derived carbon films, which were fabricated by a facile spin‐coating and following carbonization at different temperatures of 300–1,000°C. For the purpose, poly[3‐(4‐nitrilophenoxy)phenylenenitrilomethine‐1,3‐phenylenemethine] (mPAME) with a high residue of ~56.4 wt% after carbonization at 1,000°C was synthesized for a polymeric precursor for carbon films. The X‐ray photoelectron spectroscopy, Raman spectroscopy, and X‐ray diffraction analyses revealed that the molecular structures of mPAME films changed into an intrinsically nitrogen‐doped graphitic structure, dominantly at the carbonization temperatures of 800–100°C. The electrical conductivity increased considerably from ~10−7 S/cm for mPAME‐derived films fabricated at 300–700°C to ~100 S/cm for the film carbonized at 800°C to ~101 S/cm for the films carbonized at 900–1,000°C. Accordingly, mPAME‐derived carbon films, which were carbonized at 900–1,000°C, exhibited excellent electrothermal performance, such as rapid temperature responsiveness, high maximum temperatures, and high electric power efficiency to relatively low applied voltages of 5–13 V.

Synthesis and Characterization of Aromatic Poly(azomethine ether)s with Different meta- and para-Phenylene Linkage Contents

New aromatic poly(azomethine ether)s (PAMEs) bearing different meta- and para-phenylene linkage ratios in the main chains were synthesized via solution polycondensation reactions of terephthalaldehyde and/or isophthaldehyde with 3,4′-diaminodiphenyl ether. The molecular structures, thermal stability, thermo-mechanical and optical properties of the synthesized PAME homopolymers and copolymers were investigated by using FT-IR, TGA, DMA, and UV-visible/ fluorescence spectroscopy, respectively. The synthesized PAMEs were characterized to be thermally stable up to ~400 °C under nitrogen or air atmosphere and to have high char residues of above 55 % at 800 °C under nitrogen condition. The DMA data revealed that the glass transition temperatures of PMAEs are in the range of 150–200 °C, depending on the relative contents of meta- and para-phenylene linkages. The maximum absorption wavelength of transparent yellowish PAME films was detected at 410±10 nm. In addition, all PAME films exhibited a broad visible emission band at 500–800 nm and two infrared emission bands at 800–1400 nm. The synthesized PAMEs with high thermal stability and thermo-mechanical performance can be thus used as functional polymeric materials for technical fibers, optoelectronic films, and carbon fiber precursors.

Synthesis and characterization of fluorinated poly(azomethine ether)s from new core-fluorinated azomethine-containing monomers

In this work, we describe the design and synthesis of novel core-fluorinated Schiff base monomers and conjugated polymers based on them. The new fully aromatic highly fluorinated poly(azomethine ether)s (PAMEs) were prepared by polycondensation of core-fluorinated azomethine-containing compounds. The structure of the monomers and polymers were confirmed by FTIR, 1H, 13C, and 19F NMR spectroscopic analysis. The influence of synthesis condition on the properties of PAME compounds was investigated. Application of polarization microscopy with a temperature control thermal stage revealed thermotropic liquid crystalline (LC) behavior in the synthesized materials. Transition temperatures and a range of the existence of the LC phase were studied by a combination of the optical microscopy and DSC analysis. According to the TGA analysis, all the synthesized PAMEs show high thermal stability and thus offer a wide range of thermal processibility (up to 410–477 °C), which makes them prospective materials for many modern applications.

Syntheses and characterizations of oligo(azomethine ether)s derived from 2,2′-[1,4-enylenebis (methyleneoxy)]dibenzaldehyde and 2,2′-[1,2-phenylenebis (methyleneoxy)]dibenzaldehyde

The oligo(azomethine ether)s were synthesized via polycondensation of alkyl diamines with aromatic dialdehydes. Two series of dialdehydes, namely 2,2′-[1,2-phenylenebis(methyleneoxy)]dibenzaldehyde [2,2′-1,2-(PBMODB)] and 2,2′-[1,4-phenylenebis(methyleneoxy)]dibenzaldehyde [2,2′-1,4-(PBMODB)] were prepared from the condensation reactions of salicylaldehyde with o-xylenedibromide and p-xylenedibromide, respectively. The structures of dialdehydes and oligomers were determined by FT-IR, 1H-NMR and 13C-NMR. The thermal analyses of oligomers were conducted by DSC and TG/DTA techniques, respectively. Size exclusion chromatography (SEC) technique was also used to determine molecular weights and molecular weight distributions of oligomers. Electrochemical properties of the synthesized products were investigated.

Novel blue and red electrochromic poly(azomethine ether)s based on electroactive triphenylamine moieties

Two series of red and blue electrochromic aromatic poly(azomethine ether)s (PAMEs) containing electroactive triphenylamine (TPA) moieties in the backbone were prepared from the high-temperature polycondensation reactions of newly azomethine–triphenylamine (AM–TPA)-based biphenol monomers, 4,4′-di(4-hydroxybenzylideneamino)triphenylamine ( 3) and 4,4′-di(4-hydroxybenzylideneamino)-4″-methoxytriphenylamine ( 4), with difluoro compounds, respectively. The obtained polymers were readily soluble in many organic solvents and showed useful levels of thermal stability associated with high softening temperatures (215–240 °C) and high char yields (higher than 64% at 800 °C in nitrogen). In addition, the polymer films showed reversible electrochemical oxidation with high contrast ratio and unique anodic blue/red electrochromic behaviors.

Syntheses, structures and properties of novel oligo(azomethine ether)s containing or not chlorine atoms in the main chain

New oligoazomethines were synthesized via polycondensation of aromatic diamines with one of two dialdehydes. Both dialdehydes, namely 4-({2-[(4-formylphenoxy)methyl]benzyl}oxy)benzaldehyde (2-FPMBB), and 4-({4-[(4-formylphenoxy)methyl]benzyl)oxy)benzaldehyde (4-FPMBB) were prepared from p-hydroxybenzaldehyde with o-xylenedibromide or p-xylenedibromide, respectively. Dialdehydes and oligomers were characterized by FT-IR, 1 H NMR and 13 C NMR methods. Size exclusion chromatography (SEC) technique was used to determine molecular weights and molecular weight distributions of synthesized oligomers. The thermal stability of oligomers was conducted by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The weight losses of oligoazomethines (O1,O2,O3 and 04) at 1000 °C were found to be 54.74, 46.27, 54.85 and 53.10 % respectively. In all cases, the imine (-HC=N-) linkage is the first breaking group due to the high temperature. It can be seen from TGA that oligo(azomethine ether)s containing chlorine atoms have higher thermal stability at 1000 °C than O1 and 03 oligomers.

Inclusion Compounds Formation of Poly(azomethine ether)s and β‐Cyclodextrin

In this study, two poly(azomethine ether)s were synthesized and they can form inclusion compounds (ICs) with β‐cyclodextrin (β‐CD). Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance spectroscopy (1H‐NMR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) have been utilized to observe the formation of polymer‐CD‐ICs. The differentiation in their FTIR spectra may indicate the formation of the inclusion compounds between poly(azomethine ether)s and β‐CD. Compared the 1H‐NMR of polymer‐CD‐ICs with β‐CD, proton signals belonging to both β‐CD and poly(azomethine ether)s can be found in the spectrum. The chemical shift of the protons H‐3, H‐5 has changed after the formation of inclusion compounds, which is perhaps due to the interaction of these protons with polymers. TGA scans showed the much higher decomposition temperatures observed for two polymer‐CD‐ICs may imply that polymer chains included inside the β‐CD's cavity can greatly improve β‐CD's stabilities. The X‐ray diffraction patterns were confirmed to be the new crystal structures.

Synthesis and characterization of thermotropic liquid crystalline poly(azomethine ether)s

Two series of monomers, namely 4,4′-diformyl-α,ω-diphenoxydecane and 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane, were prepared from 1,10-dibromodecane with p-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde (vanillin), respectively. The poly(azomethine ether)s were prepared by solution polycondensation using 4,4′-diformyl-α,ω-diphenoxydecane, 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane with various diamines. The monomers and polymers were characterized by intrinsic viscosity, FT-IR, 1H, and 13C NMR spectroscopy. The thermogravimetric analysis reveals that the polymers are stable up to 320–500°C and decomposed with good char yield. The thermotropic liquid crystalline properties of the polymers were examined by differential scanning calorimetry (DSC) and their textures observed under hot stage optical polarized microscopy (HOPM). All the polymers were exhibited thermotropic liquid crystalline properties except tetramethylene diamines-based polymers.

Thermophysical properties of azomethine ether main-chain liquid crystalline polymers at pressures to 200 MPa

This article reports on an experimental investigation of the equation of state and the transition behavior of main-chain thermotropic liquid crystalline polymers over a wide temperature range, and at pressures to 200 MPa. The materials studied were a series of azomethine ether polymers. A varying number n (= 4, 7, 8, 9, 10 and 11) of methylene spacer units in the backbone provided systematic variation of the structure. Experimental techniques used included high-pressure dilatometry (PVT measurements) to 200 MPa, high-pressure differential thermal analysis, also to 200 MPa, and conventional (atmospheric-pressure) differential scanning calorimetry (DSC). The equation of state of the materials can be well represented by the Tait equation in distinct regions, separated by a glass transition, Tg(P), a first-order transition to a nematic state, Tk-n(P), and a first-order transition to an isotropic melt state Tc(P). The atmospheric pressure values of Tk-n and Tc decreased with increasing number of spacer units and showed a clear odd-even effect. Tg and Tk-n both increased with pressure. The pressure dependence of Tc could not be observed due to the onset of degradation in the same temperature region. On isobaric cooling at 3°C/min, the crystallization from the nematic state occurred a few tens of degrees below Tk-n. This supercooling was independent of pressure for some materials, while for others it increased with increasing pressure. The values of the enthalpy and entropy associated with the first-order transition into the nematic state were lower than those of typical isotropic polymers at their melting transitions. The transition enthalpy did not have any systematic variation with increasing number of spacer units. Values of the transition enthalpy calculated from the Ciapeyron equation did not always agree with the values measured by DSC. This may be due to the two-phase nature of the low-temperature state. At the transition to the isotropic state, the transition enthalpy at P = 0 decreased with n and showed an odd-even effect. © 1994 John Wiley & Sons, Inc.

Microphase separation behaviour in a series of thermotropic liquid crystalline copolyethers

The phase transition and microphase separation behaviour have been studied by means of differential scanning calorimetry, polarizing microscopy, depolarizing transmittance and X-ray diffraction measurements for a series of thermotropic liquid crystalline random copolyethers. These are composed of two similar aromatic azomethine ether units, derived from 3,3′-dimethoxy-4,4′-diformyl-α,ω-diphenoxyhexane with 4,4′-diaminodiphenylmethane (system A) and with 4,4′-phenylenediamine (system B). These copolymers, with the exception of those containing a high content of the A component, were found to transform from a crystalline to a nematic liquid crystalline, and finally to an isotropic phase. For the specimens with 40, 50 and 60 mol% of the A component a microphase separation phenomenon was distinctly observed: segments of the A and B components along the polymer backbones may separately form their own crystalline domains, which melt in different temperature ranges. After this, the A domains are transformed directly into the isotropic state, while the B segments can still form special mesomorphic domains. A phase diagram for these copolymers was also obtained: the melting points of the crystalline domains formed by segments of the A component were found to be only slightly changed with variation in the component content, while the melting and the isotropization transition temperatures of the B component domains were lowered significantly with decreases in the B component content.

Regular, adjacent reentry folding in single crystals of a liquid crystal polymer crystallized from the nematic state

AbstractFolded chain single crystals 35 Å thick have been grown from the liquid crystal state of an aromatic‐aliphatic azomethine ether polymer (AZMEP‐n) having a 10‐carbon flexible segment (n = 10). Electron diffraction has permitted refinement of the triclinic unit cell. The molecular axes lie at an ca. 65° angle to the lamella normal and fold every third chemical repeat distance. For AZMEP‐1 and ‐8 extended chain lamellae are formed; for AZMEP‐7 both folded and extended chain lamellae are found. The observations of folded chain lamallae are in agreement with prior suggestions from our laboratory of chain folding in the liquid crystalline state in thin films. © 1992 John Wiley & Sons, Inc.

PVT properties of main-chain liquid-crystalline polymers

The densities, as a function of temperature and pressure, of several main-chain liquid-crystalline polymers were measured. The polymers were a copolyester and a series of azomethine ether polymers containing flexible spacer groups along the chain. An equation-of-state theory was developed, which was based on a cell model where expansion of the lattice occurred only in two dimensions. The ability of the theory to describe the PVT properties was investigated and compared to a simple cell model that has been used for flexible polymers. It was found that the liquid-crystal cell model described the PVT properties of the liquid-crystalline polymers better than the simple cell model. The fit became worse for polymers with flexible spacing groups, and the equation did not describe flexible polymers such as polyethylene. It is inferred that the liquid-crystal model gives a better physical description of the structure of rigid polymers.

Aromatic-aliphatic azomethine ether polymers and fibers

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAromatic-aliphatic azomethine ether polymers and fibersPaul W. WojtkowskiCite this: Macromolecules 1987, 20, 4, 740–748Publication Date (Print):April 1, 1987Publication History Published online1 May 2002Published inissue 1 April 1987https://doi.org/10.1021/ma00170a007RIGHTS & PERMISSIONSArticle Views256Altmetric-Citations67LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts