Synthesis and photophysical study of new blue fluorescent poly(azomethine-1,3,4-oxadiazole)s containing dimethylamino groups

2017 ◽  
Vol 30 (3) ◽  
pp. 339-346 ◽  
Author(s):  
Elena Hamciuc ◽  
Mihaela Homocianu ◽  
Corneliu Hamciuc ◽  
Ionela-Daniela Carja
Keyword(s):  
Stokes Shift ◽  
Solvent Polarity ◽  
Decomposition Temperature ◽  
Photoluminescence Spectra ◽  
Polar Solvents ◽  
Initial Decomposition Temperature ◽  
Yield Values ◽  
Photophysical Study ◽  
Hcl Concentration ◽  
Terephthalic Aldehyde

New aromatic polyazomethines were synthesized by polycondensation reaction of a diamine containing 1,3,4-oxadiazole ring, namely, 4,4′-diamino-4″-[2-(4-phenoxy)-5-(4-dimethylaminophenyl)-1,3,4-oxadiazole)]triphenylmethane, with terephthalic aldehyde or bis(4-formylphenoxyphenyl)fluorene, by using N-methyl-2-pyrrolidinone (NMP) as solvent. The polymers were easily soluble in polar solvents, such as NMP, N, N-dimethylacetamide, or chloroform, and showed high thermal stability with the initial decomposition temperature above 415°C and the temperature of 10% weight loss in the range of 450–460°C. They exhibited high char yield at 800°C in the range of 52–56%. Optical properties were studied by absorption and photoluminescence spectra. In solution, the polymers presented two absorption maxima in the ranges 273–278 and 330–346 nm and emitted violet-blue light in the range of 413–468 nm, depending on the solvent polarity. The Stokes shift and emission quantum yield values depend on the polymer structure and solvent polarity. The emission intensity in NMP solution was enhanced upon increasing the HCl concentration, while the absorption spectral profile was slightly influenced.

scholarly journals Synthesis and Photophysical and Electrochemical Properties of Pyridine-, Pyrazine- and Triazine-based (D-π-)2A Fluorescent Dyes

2019 ◽  
Author(s):  
Keiichi Imato ◽  
Toshiaki Enoki ◽  
Koji Uenaka ◽  
Yousuke Ooyama
Keyword(s):  
Cyclic Voltammetry ◽  
Energy Level ◽  
Electrochemical Properties ◽  
Density Functional ◽  
Fluorescent Dyes ◽  
Bathochromic Shift ◽  
Stokes Shift ◽  
Solvent Polarity ◽  
Polar Solvents ◽  
Lumo Energy

Donor–acceptor–π-conjugated (D–π–)2A fluorescent dyes OUY-2, OUK-2 and OUJ-2 with two (diphenylamino)carbazole-thiophene units as D (electron-donating group)–π (π-conjugated bridge) moiety and a pyridine, pyrazine or triazine ring as electron-withdrawing group (electron-accepting group; A) have been designed and developed and their photophysical and electrochemical properties were investigated based on the photoabsorption and fluorescence spectroscopy, Lippert–Mataga plots, cyclic voltammetry and density functional theory calculations. The photoabsorption maximum (λ abs max) and the fluorescence maximum (λ fl max) for the intramolecular charge-transfer characteristic band of the (D–π–)2A fluorescent dyes show bathochromic shift in the order of OUY-2 < OUK-2 < OUJ-2. Moreover, the photoabsorption spectra of the (D–π–)2A fluorescent dyes are nearly independent of solvent polarity, while their fluorescence maxima bathochromically shifted with increasing solvent polarity (i.e., positive fluorescence solvatochromism). The Lippert–Mataga plots for OUY-2, OUK-2 and OUJ-2 indicate that the Δμ (= μ e ‒ μ g) value, which is the difference in the dipole moment of the dye between the excited (μ e) and the ground (μ g) states, increases in the order of OUY-2 < OUK-2 < OUJ-2, that is, the fact explains our findings that OUJ-2 shows large bathochromic shifts in their fluorescence maxima in polar solvents and that the Stokes shift values for OUJ-2 in polar solvents are much larger than those in nonpolar solvents. The cyclic voltammetry of OUY-2, OUK-2 and OUJ-2 demonstrated that there is little difference in the HOMO energy level among the three dyes, but the LUMO energy levels decrease in the order of OUY-2 > OUK-2 > OUJ-2. Consequently, this work reveals that for the (D–π–)2A fluorescent dyes OUY-2, OUK-2 and OUJ-2 the bathochromic shifts of λ abs max and λ fl max and the lowering of the LUMO energy level are dependent on the electron-withdrawing ability of azine ring, which increases in the order of OUY-2 < OUK-2 < OUJ-2.

scholarly journals Synthesis, photophysical and electrochemical properties of pyridine, pyrazine and triazine-based (D–π–)2A fluorescent dyes

2019 ◽  
Vol 15 ◽  
pp. 1712-1721 ◽  
Author(s):  
Keiichi Imato ◽  
Toshiaki Enoki ◽  
Koji Uenaka ◽  
Yousuke Ooyama
Keyword(s):  
Cyclic Voltammetry ◽  
Energy Level ◽  
Electrochemical Properties ◽  
Density Functional ◽  
Fluorescent Dyes ◽  
Stokes Shift ◽  
Solvent Polarity ◽  
Polar Solvents ◽  
Lumo Energy ◽  
Fluorescence Maximum

The donor–acceptor–π-conjugated (D–π–)2A fluorescent dyes OUY-2, OUK-2 and OUJ-2 with two (diphenylamino)carbazole thiophene units as D (electron-donating group)–π (π-conjugated bridge) moiety and a pyridine, pyrazine or triazine ring as electron-withdrawing group (electron-accepting group, A) have been designed and synthesized. The photophysical and electrochemical properties of the three dyes were investigated by photoabsorption and fluorescence spectroscopy, Lippert–Mataga plots, cyclic voltammetry and density functional theory calculations. The photoabsorption maximum (λmax,abs) and the fluorescence maximum (λmax,fl) for the intramolecular charge-transfer characteristic band of the (D–π–)2A fluorescent dyes show bathochromic shifts in the order of OUY-2 < OUK-2 < OUJ-2. Moreover, the photoabsorption bands of the (D–π–)2A fluorescent dyes are nearly independent of solvent polarity, while the fluorescence bands showed bathochromic shifts with increasing solvent polarity (i.e., positive fluorescence solvatochromism). The Lippert–Mataga plots for OUY-2, OUK-2 and OUJ-2 indicate that the Δμ (= μe − μg) value, which is the difference in the dipole moment of the dye between the excited (μe) and the ground (μg) states, increases in the order of OUY-2 < OUK-2 < OUJ-2. Therefore, the fact explains our findings that OUJ-2 shows large bathochromic shifts of the fluorescence maxima in polar solvents, as well as the Stokes shift values of OUJ-2 in polar solvents are much larger than those in nonpolar solvents. The cyclic voltammetry of OUY-2, OUK-2 and OUJ-2 demonstrated that there is little difference in the HOMO energy level among the three dyes, but the LUMO energy levels decrease in the order of OUY-2 > OUK-2 > OUJ-2. Consequently, this work reveals that for the (D–π–)2A fluorescent dyes OUY-2, OUK-2 and OUJ-2 the bathochromic shifts of λmax,abs and λmax,fl and the lowering of the LUMO energy level are dependent on the electron-withdrawing ability of the azine ring, which increases in the order of OUY-2 < OUK-2 < OUJ-2.

Study on Synthesis and Thermal Property of Polyvinylamine

2010 ◽  
Vol 150-151 ◽  
pp. 1500-1503 ◽  
Author(s):  
Hong Chi Zhao ◽  
Qi Li ◽  
Wen Yu Xu ◽  
Fan Huang
Keyword(s):  
Decomposition Temperature ◽  
Characteristic Peak ◽  
Initial Decomposition Temperature ◽  
Nmr Spectrum ◽  
X Ray ◽  
Nuclear Magnetic Resonance Spectrometer ◽  
Chemical Structures ◽  
Thermogravimetric Analyzer ◽  
Infrared Spectrometer ◽  
Thermal Stability Of

Polyvinylamine (PVAm) and polyvinylamine chloride (PVAm•HCl) were synthesized by Hofmann degradation of polyacrylamide (PAM). The reaction condition is gentle and the operation is safe, simple and economical so that it is a good reaction method. The chemical structures and thermal properties of the polymers were studied by Fourier transform infrared spectrometer (FTIR), nuclear magnetic resonance spectrometer (NMR), X-ray diffractmeter (XRD) and thermogravimetric analyzer (TGA). Synthesis of PVAm•HCl was confirmed by the intensities of the characteristic peak of -CONH2 decreased and the appearance of a new absorption peak at 1530cm-1 (due to N-H bond of -NH3+ ) in the FTIR spectrum, the appearance of the characteristic absorption peaks of carbon atoms in the 13C NMR spectrum, the appearance of chemical shift assignments of proton in 1H NMR spectrum and the appearance of characteristic dispersing diffraction peak between 22.5° to 25.2° in the XRD spectrum, respectively. PAM had three decomposing stages, but PVAm•HCl had two decomposing stages. TG curve of PAM and PVAm•HCl showed that the initial decomposition temperature were 190oC and 140oC, respectively. The thermal stability of PVAm•HCl was poorer than that of PAM.

Polyimide nanocomposites with functionalized graphene sheets

2017 ◽  
Vol 31 (6) ◽  
pp. 837-861 ◽  
Author(s):  
Jin-Hae Chang
Keyword(s):  
Electrical Conductivity ◽  
Filler Content ◽  
Coefficient Of Thermal Expansion ◽  
Barrier Properties ◽  
Decomposition Temperature ◽  
Graphene Sheets ◽  
Functionalized Graphene ◽  
Hybrid Films ◽  
Initial Decomposition Temperature ◽  
Transmission Electron Microscopy Analysis

Polyimide (PI) nanocomposites containing two different functionalized graphene sheets (FGSs) were synthesized, and their thermal properties, morphology, oxygen permeability, and electrical conductivity were compared. Hexadecylamine–graphene sheets and 4-amino- N-hexadecylbenzamide–graphene sheets were utilized. Hybrid films were obtained from blended solutions of PI and FGSs, with the filler content with respect to the PI varying from 0 wt% to 10 wt%. The differences in the properties of the PI matrix were then analyzed with respect to filler content. Transmission electron microscopy analysis confirmed that the two FGSs were dispersed homogeneously throughout the polymer matrix, although some FGS aggregates were also formed. Furthermore, it was observed that the addition of small amounts of FGS nanofiller was sufficient to improve the coefficient of thermal expansion, the gas barrier properties, and the electrical conductivity of the hybrid films. In contrast, the glass transition temperature and the initial decomposition temperature of the PI hybrid films continued to decrease with increasing FGS content.

scholarly journals Preparation of Few-Layered WS2 and Its Thermal Catalysis for Dihydroxylammonium-5,5′-Bistetrazole-1,1′-Diolate

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Yiping Shang ◽  
Wu Yang ◽  
Yabei Xu ◽  
Siru Pan ◽  
Huayu Wang ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Thermal Decomposition ◽  
Analysis Data ◽  
Decomposition Temperature ◽  
Thermal Excitation ◽  
Layered Semiconductor ◽  
Initial Decomposition Temperature ◽  
Thermal Decomposition Behavior ◽  
Decomposition Behavior ◽  
Catalytic Effects

In this study, few-layered tungsten disulfide (WS2) was prepared using a liquid phase exfoliation (LPE) method, and its thermal catalytic effects on an important kind of energetic salts, dihydroxylammonium-5,5′-bistetrazole-1,1′-diolate (TKX-50), were investigated. Few-layered WS2 nanosheets were obtained successfully from LPE process. And the effects of the catalytic activity of the bulk and few-layered WS2 on the thermal decomposition behavior of TKX-50 were studied by using synchronous thermal analysis (STA). Moreover, the thermal analysis data was analyzed furtherly by using the thermokinetic software AKTS. The results showed the WS2 materials had an intrinsic thermal catalysis performance for TKX-50 thermal decomposition. With the few-layered WS2 added, the initial decomposition temperature and activation energy (Ea) of TKX-50 had been decreased more efficiently. A possible thermal catalysis decomposition mechanism was proposed based on WS2. Two dimensional-layered semiconductor WS2 materials under thermal excitation can promote the primary decomposition of TKX-50 by enhancing the H-transfer progress.

scholarly journals A Study on the Synthesis, Curing Behavior and Flame Retardance of a Novel Flame Retardant Curing Agent for Epoxy Resin

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 245
Author(s):  
Yong Sun ◽  
Yongli Peng ◽  
Yajiao Zhang
Keyword(s):  
Flame Retardant ◽  
Epoxy Resin ◽  
Decomposition Temperature ◽  
Isothermal Kinetics ◽  
Flame Retardance ◽  
Curing Agent ◽  
Initial Decomposition Temperature ◽  
Limiting Oxygen Index ◽  
Epoxy Resin System ◽  
Dsc Method

In this work, a flame retardant curing agent (DOPO-MAC) composed of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO and methyl acrylamide (MAC) was synthesized successfully, and the structure of the compound was characterized by FT-IR and 1H-NMR. The non-isothermal kinetics of the epoxy resin/DOPO-MAC system with 1% phosphorus was studied by non-isothermal DSC method. The activation energy of the reaction (Ea), about 46 kJ/mol, was calculated by Kissinger and Ozawa method, indicating that the curing reaction was easy to carry out. The flame retardancy of the epoxy resin system was analyzed by vertical combustion test (UL94) and limiting oxygen index (LOI) test. The results showed that epoxy resin (EP) with 1% phosphorus successfully passed a UL-94 V-0 rating, and the LOI value increased along with the increasing of phosphorus content. It confirmed that DOPO-MAC possessed excellent flame retardance and higher curing reactivity. Moreover, the thermal stability of EP materials was also investigated by TGA. With the DOPO-MAC added, the residual mass of EP materials increased remarkably although the initial decomposition temperature decreased slightly.

scholarly journals Studies on Photophysical Properties of Mono-carbonyl Curcumin Analogues: Experimental and Theoretical approach

2018 ◽  
Vol 34 (4) ◽  
pp. 2170-2179
Author(s):  
Manjula Rayanal ◽  
Prasad Pralhad Pujar ◽  
Sridhar D
Keyword(s):  
Excited State ◽  
Ground State ◽  
Dipole Moments ◽  
Photophysical Properties ◽  
Stokes Shift ◽  
Solvent Polarity ◽  
Frontier Molecular Orbital ◽  
Curcumin Analogues ◽  
Td Dft ◽  
Ground State Dipole Moments

The solvatochromic fluorescence behaviour of mono-carbonyl curcumin analogues has been studied in ten different solvents ranging from non-polar to polar. The solvent effect on the spectral properties of analogues has been discussed. The ground state dipole moments were estimated experimentally by Bilot-Kawski equation which is a function of Stokes shift with the solvent polarity parameters and Guggenheim method and theoretically by TD-DFT studies. The excited state dipole moment was determined using Bilot-Kawski equations. The excited state dipole moments for the two molecules were found to be higher than their corresponding ground state dipole moments. Theoretically Frontier molecular orbital (HOMO/ LUMO) energies were determined by Gaussian 09 W software using TD-DFT.

scholarly journals Effects of Solvent Polarity on Solvation Free Energy, Dipole Moment, Polarizability, Hyperpolarizability and Molecular Properties of Metronidazole

2016 ◽  
Vol 19 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Mohammad Firoz Khan ◽  
Ridwan Bin Rashid ◽  
Md Yeunus Mian ◽  
Mohammad S Rahman ◽  
Mohammad A Rashid
Keyword(s):  
Free Energy ◽  
Dipole Moment ◽  
Gas Phase ◽  
Chemical Potential ◽  
Solvent Polarity ◽  
Solvation Free Energy ◽  
Molecular Properties ◽  
Chemical Hardness ◽  
Electrophilicity Index ◽  
Polar Solvents

A computational study of medium effect on solvation free energy, dipole moment, polarizability, hyperpolarizability and different molecular properties like chemical hardness & softness, chemical potential, electronegativity and electrophilicity index of metronidazole have been reported in this paper. Becke, 3-parameter, Lee-Yang-Parr (B3LYP) level of theory with 6-31G (d,p) basis set was applied for gas phase and solution. The effect of solvent polarity on solvation free energy, dipole moment, polarizability, hyperpolarizability and molecular properties were calculated by employing Solvation Model on Density (SMD). The solvation free energies and dipole moment of metronidazole were found to be increased in nonpolar to polar solvents. The dipole moment of metronidazole was higher in different solvent than that of the gas phase. Moreover, from non-polar to polar solvents the chemical potential, electronegativity and electrophilicity index were increased. On the other hand, opposite relation was found in the case of chemical hardness and softness. The results obtained in this study may lead to understand the stability and reactivity of metronidazole and the results will be of assistance to use the title molecule as reaction intermediates and pharmaceuticals.Bangladesh Pharmaceutical Journal 19(1): 9-14, 2016

scholarly journals The Synthesis of Magnesium Soaps as Feed for Biohydrocarbon Production

2018 ◽  
Vol 156 ◽  
pp. 03001 ◽  
Author(s):  
Meiti Pratiwi ◽  
Godlief F. Neonufa ◽  
Tirto Prakoso ◽  
Tatang H. Soerawidjaja
Keyword(s):  
Coconut Oil ◽  
Decomposition Temperature ◽  
Direct Reaction ◽  
Initial Decomposition Temperature ◽  
Process Yield ◽  
Palm Stearine ◽  
Metal Soaps ◽  
Amorphous Surface ◽  
Great Potency

In previous study, by heating magnesium basic soaps from palm stearine will decarboxylated and produced biohydrocarbon. The frequent method to produced metal soaps from triglyceride in laboratory scale is metathesis. This process is less favored because this method would produced large amounts of salt waste and hard to develop into bigger scale. This study investigated the process and characterization of magnesium soaps from coconut oil and magnesium hydroxide via direct reaction method at 185 °C for 3 and 6 hours. The resulting soaps were washed with water and methanol, then dried. This process yield more than 80%-w metal soaps, acid values lower than 6 mg KOH/g and pH 9.2. Based on Thermogravimetry Analysis (TGA) and SEM results, the initial decomposition temperature of these metal soaps were at 300 °C and have amorphous surface morphology. From decarboxylation test of magnesium basic soaps indicate great potency as feed for biohydrocarbon production.

INFLUENCE OF NANOFILLER ON THERMAL DEGRADATION RESISTANCE OF HYDROGENATED NITRILE BUTADIENE RUBBER

2018 ◽  
Vol 92 (2) ◽  
pp. 263-285 ◽  
Author(s):  
Tuhin Saha ◽  
Anil K. Bhowmick
Keyword(s):  
Atomistic Simulation ◽  
Model Compound ◽  
Degradation Mechanism ◽  
Decomposition Temperature ◽  
Industrial Applications ◽  
Gas Chromatography Mass Spectrometry ◽  
Butadiene Rubber ◽  
Pyrolysis Gas ◽  
Initial Decomposition Temperature ◽  
Acrylonitrile Butadiene Rubber

ABSTRACT Studies on the degradation of elastomers and their prevention have become increasingly important in recent years because of stringent environmental conditions in many industrial applications. The reactive atomistic simulation was executed on a hydrogenated acrylonitrile-butadiene rubber (HNBR40) model compound composed of 40 monomer units. The reactive simulation was used to study the decomposition behavior of HNBR40, to visualize different pyrolysis products, and also to analyze the degradation mechanism of HNBR40. Ethylene, propylene, and acrylonitrile were observed as dominant products at lower temperature, and 1-butene was found at higher temperature. Pyrolysis–gas chromatography–mass spectrometry was used to verify the decomposition products obtained from the prediction of atomistic simulation. In this study, nanofillers, especially nanoclays and nanosilicas, were used to prevent degradation significantly. Restricted degradation by the nanofiller-reinforced rubber prolonged the durability. Furthermore, the reactive simulation was performed to understand thermal decomposition characteristics of the model compound in the presence of the nanofiller. The initial decomposition temperature, the final degradation temperature, and the rate of degradation improved to a great extent on the addition of the model nanosilica compound as obtained from the simulation studies. Moreover, the lifetime of nanoclay- and nanosilica-reinforced hydrogenated acrylonitrile–butadiene rubber was calculated by using thermogravimetric analysis, and its useful lifetime was compared with that of the pristine polymer in the application temperature range of 150 °C.

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