Formation of 2,3-diaminophenazines and their self-assembly into nanobelts in aqueous medium

One-dimensional (1D) nanobelts of several hundred micrometers in length, several hundred nanometers in width and several hundred nanometers in height are obtained by direct mixing of ortho-phenylenediamine (oPD) and FeCl₃ aqueous solution at room temperature. The nanobelts were characterized by elemental analysis, liquid chromatography/mass spectrometry (LC/MS), NMR (¹H and ¹³C), FT-IR, UV-vis, thermogravimetric (TG) and conductivity measurement. The nanobelts are identified as 2,3-diaminophenazine assemblies. The formation of the nanobelts involves two stages: (1) oxidation of oPD by FeCl₃, yielding individual 2,3-diaminophenazine molecules; and (2) self-assembly of the 2,3-diaminophenazine, forming the 1D nanobelts. The nanobelts exhibit fairly high thermal stability and show conductivity at the level of semiconductors.     

Thermal properties and flame retardancy of novel epoxy based on phosphorus‐modified Schiff‐base

Through addition reaction of Schiff‐base terephthalylidene‐bis‐(p‐aminophenol) ( DP‐1 ) and diethyl phosphite (DEP), a novel phosphorus‐modified epoxy, 4,4'‐diglycidyl‐(terephthalylidene‐bis‐(p‐aminophenol))diphosphonate ether ( EP‐2 ), was obtained. An modification reaction between EP‐2 and DP‐1 resulted in an epoxy compound, EP‐3 , possessing both phosphonate groups and C?N imine groups. The structure of EP‐2 was characterized by Fourier transform infrared (FTIR), elemental analysis (EA), ¹H, ¹³C, and ³¹P NMR analyses. The thermal properties of phosphorus‐modified epoxies cured with 4,4'‐diaminodiphenylmethane (MDA) and 4,4'‐diaminodiphenyl ether (DDE) were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The activation energies of dynamic thermal degradation (E_d) were calculated using Kissinger and Ozawa's methods. The thermal degradation mechanism was characterized using thermogravimetric analysis/infrared spectrometry (TG‐IR). In addition, the flame retardancy of phosphorus‐modified epoxy thermosets was evaluated using limiting oxygen index (LOI) and UL‐94 vertical test methods. Via an ingenious design, phosphonate groups were successfully introduced into the backbone of the epoxies; the flame retardancy of phosphorus‐modified epoxy thermosets was distinctly improved. Due to incorporation of C?N imine group, the phosphorus‐modified epoxy thermosets exhibited high thermal stabilities; the values of glass‐transition temperatures (T_gs) were about 201–210°C, the values of E_d were about 220–490 kJ/mol and char yields at 700°C were 49–53% in nitrogen and 45–50% in air. These results showed an improvement in the thermal properties of phosphorus‐modified epoxy by the incorporation of C?N imine groups. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation and Properties of Novel Cyclophosphazenes Containing Cyanato Groups

Abstract

Novel cyclotriphosphazenes containing cyanato group (PZCN) derivatives were synthesized by a substitution reaction of 4-hydroxyphenoxycyclotriphosphazenes and cyanogen bromide (BrCN) in the presence of triethylamine (TEA). The PZCNs were characterized by FT-IR, liquid chromatography–mass spectrometry (LC-MS), ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopy. Curing reactions of the PZCNs were evaluated by FT-IR spectroscopy, thermogravimetry/differential thermal analysis (TG/DTA), and differential scanning, calorimetry (DSC). The PZCNs exhibited an exothermic peak due to curing within the temperature range of 140–300°C by DSC. The PZCNs were completely cured at 220°C. The cured PZCNs exhibited high thermal stability up to 350°C, a high char-forming capability, and electrical properties, such as dielectric constants (Dks) between 2.68 and 2.87, and dissipation factors (Dfs) between 0.008 and 0.013 at 1 MHz.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Tetraanionic Nitrogen‐Rich Tetrazole‐Based Energetic Salts

1,1,3,3‐Tetra(1H‐tetrazol‐5‐yl)propane‐based energetic salts were synthesized in a simple and straightforward manner. The structures of these new salts were determined by ¹H and ¹³C NMR spectroscopy, IR spectroscopy, MS, and elemental analysis. All of these compounds showed good thermal stabilities above 180 °C, as confirmed by thermogravimetric–differential thermal analysis (TG–DTA) measurements. Moreover, these salts also exhibited high positive enthalpies of formation, high nitrogen content, good thermal stabilities, and moderate detonation properties.     

Synthesis, curing kinetics and thermal properties of bisphenol-AP-based benzoxazine

A novel bisphenol-AP-aniline-based benzoxazine monomer (B-AP-a) was synthesized from the reaction of 4,4′-(1-phenylethylidene) bisphenol (bisphenol-AP) with formaldehyde and aniline. The chemical structures were identified by FT-IR, ¹H and ¹³C NMR analyses. The polymerization behavior of the monomer and the types of hydrogen bonding species were monitored by differential scanning calorimetry (DSC) and FT-IR. The curing kinetics was studied by isothermal DSC and the isothermal kinetic parameters were determined. The thermal properties of cured benzoxazine were measured by DSC and thermogravimetric analysis (TGA). The bisphenol-AP-aniline-based polybenzoxazine (poly(B-AP-a)) exhibited higher glass transition temperature (T_g) and better thermal stability than corresponding bisphenol A-aniline-based polybenzoxazines (poly(BA-a)). The T_g value of poly(B-AP-a) is 171 °C. The temperatures corresponding to 5% and 10% weight loss is 317 and 347 °C, respectively, and the char yield is 42.2% at 800 °C. The isothermal curing behavior of B-AP-a displayed autocatalysis and diffusion control characteristics. The modified autocatalytic model showed good agreement with experimental results.     

Preparation and properties of polyesters from diphenylmethane-4,4′-di(methylthiopropionic acid) and aliphatic diols

The new linear polyesters containing sulfur in the main chain were obtained by melt polycondensation of diphenylmethane-4,4′-di(methylthiopropionic acid) with ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-propanediol, 1,3-butanediol, and 2,2′-oxydiethanol. Low-molecular weights, low-softening temperatures and, very good solubility in organic solvents are their characteristics. The structure of all polyesters was determined by elemental analysis, FT-IR and ¹H-NMR spectroscopy, and x-ray diffraction analysis. The thermal behavior of these polymers was examined by differential thermal analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The kinetics of polyesters formation by uncatalyzed melt polycondensation was studied in a model system: diphenylmethane-4,4′-di(methylthiopropionic acid) and 1,4-butanediol or 2,2′-oxydiethanol at 150, 160, and 170°C. Reaction rate constants (k₃) and activation parameters (ΔG^≠, ΔH^≠, ΔS^≠) from carboxyl group loss were determined using classical kinetic methods. © 1997 John Wiley & Sons, Inc.     

Polyesters containing sulfur. VI. Synthesis and characterization of polyesters from naphthalene-1,4- or naphthalene-1,5-bis(methylthioacetic acid) and aliphatic diols

Two series of new linear polyesters containing sulfur in the main chain were obtained by melt polycondensation of naphthalene-1,4-bis(methylthioacetic acid) (N-1,4-BMTAA) or naphthalene-1,5-bis(methylthioacetic acid) (N-1,5-BMTAA) with some aliphatic diols using a 0.05 molar excess of diol. Softening temperatures ranging from 55 to 130°C, reduced viscosities in the range of 0.15–0.39 dL/g, and low-molecular weights were their characteristic. The structure and thermal properties of all polyesters were examined by using elemental analysis, FT-IR and ¹H-NMR spectroscopy, X-ray diffraction analysis, differential thermal analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorymetry (DSC). The kinetics of polyester formation by uncatalyzed melt polycondensation was studied in a model system: N-1,4-BMTAA or N-1,5-BMTAA and 2,2′-oxydiethanol (ODE) at 150, 160, and 170°C. Reaction rate constants (k₃) and activation parameters (ΔG^‡, ΔH^‡, ΔS^‡) from carboxyl group loss were determined using classical kinetic methods. Hydroxyl-terminated polyesters derived from 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol were used for preparation of the polyurethanes by melt polyaddition with hexamethylene diisocyanate (HDI). They were characterized by reduced viscosity, FT-IR spectroscopy, X-ray diffraction analysis, TGA, DSC, polarizing microscope observation, and hardness and tensile properties. The resulting polyurethanes behave like high-elasticity thermoplastic elastomers, except the one derived from N-1,5-BMTAA and 1,6-hexanediol-based polyester. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2359–2369, 1998     

Nano lithium aluminate filler incorporating gel lithium triflate polymer composite: Preparation,characterization and application as an electrolyte in lithium ion batteries

Gel polymer composites electrolytes containing nano LiAlO₂ as filler were prepared using a solution cast technique and characterized using different techniques such as X-ray diffraction (XRD), thermal analysis (TG, DSC), Fourier transform infra – red spectroscopy (FT-IR) and scanning electron microscope (SEM). X-ray diffraction analysis showed the effect of lithium tri fluoro methane sulphonate (LiCF₃SO₃), poly vinyl acetate (PVAc) and nano lithium aluminate (LiAlO₂) on the crystalline structure of the poly vinylidene fluoride –co– hexa fluoro propylene (PVDF-co-HFP) matrix containing ethylene carbonate (EC) and diethyl carbonate (DEC) as plasticizers. FT-IR analysis confirmed both the good dissolution of the LiCF₃SO₃ salt and the good interaction of the nano LiAlO₂ filler with the polymer matrix. TG analysis showed the good thermal stability of the LiAlO₂ samples compared to the free one. Also, addition of nano LiAlO₂ filler enhanced the conductivity value of the polymer composites electrolytes. The sample containing 2 wt% of LiAlO₂ showed the highest conductivity value, 4.98 × 10⁻³ Ω ⁻¹ cm⁻¹ at room temperature, with good thermal stability behavior (T_d = 362 °C). This good conductive and thermally stable polymer nano composite electrolyte was evaluated as a promising membrane for lithium ion batteries application.     

Preparation of Poly(amic acid) and Polyimide via Microwave-Assisted Polycondensation of Aromatic Dianhydrides and Diamines

Summary: A copolycondesation-type poly (amic acid) (PAA) was synthesized using pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) as dianhydride monomers, and 4,4′-oxydianiline (ODA) as a diamine monomer under microwave irradiation in dimethylformamide (DMF). PAA was then converted into a polyimide (PI) by an imidization. The structure and performance of the polymer were characterized by Fourier-transform infrared (FT-IR) spectroscopy, Proton nuclear magnetic resonance (¹H NMR) spectrometry, viscosity, X-ray diffraction (XRD), and thermogravimetric (TG) analyses. The results showed that under microwave irradiation, the intrinsic viscosity and the yield of PAA were increases, and the reaction time was shortened. The FT-IR spectra of the polymer revealed characteristic peaks for PI around 1778^– and 1723 cm^–1. TG curves indicated that the obtained PI began to lose weight at 535 °C, and its 10% thermal decomposition temperature under N₂ was 587 °C.     

Investigation of thermal properties of some basalt samples in Egypt

This work aims in studying the temperature dependence of the thermal properties (thermal diffusivity, k, specific heat, C _p and thermal conductivity, ) of some basalt group samples, collected from different regions in the eastern desert of Egypt. The thermal properties of these samples were measured in the temperature range from r.t. to 900 K. The average values of the thermal conductivity of these investigated samples lie in the range from 0.4·10^–3 to 2.01·10^–3 cal cm^–1 s^–1 K^–1. This means that these samples are considered as thermal insulating materials. The thermogravimetric analysis (TG) confirmed that these investigated samples are dry rocks. X-ray fluorescence (XRF) and X-ray diffraction (XRD) confirmed that these rock samples have a crystalline phase, the peaks of XRD have a small change in their location as a result of heat treatment. This behaviour was attributed to the oxidation and firing of some minerals after the heat treatment.This revised version was published online in November 2005 with corrections to the Cover Date.     

Quantitative analysis of biodegradable amphiphilic poly(L-lactide)-block-poly(ethyleneglycol)-blockpoly(L-lactide) by using TG, FTIR and NMR

The thermogravimetric analysis (TG) of two series of tri-block copolymers based on poly(L,L-lactide) (PLLA) and poly(ethyleneglycol) (PEG) segments, having molar mass of 4000 or 600 g mol^–1, respectively, is reported. The prepared block copolymers presented wide range of molecular masses (800 to 47500 g mol^–1) and compositions (16 to 80 mass% PEG). The thermal stability increased with the PLLA and/or PEG segment size and the tri-block copolymers prepared from PEG 4000 started to decompose at higher temperatures compared to those copolymers from PEG 600. The copolymers compositions were determined by thermogravimetric analysis and the results were compared to other traditional quantitative spectroscopic methods, hydrogen nuclear magnetic resonance spectrometry (¹HNMR) and Fourier transform infrared spectrometry (FTIR). The PEG 4000 copolymer compositions calculated by TG and by ¹HNMR, presented differences of 1%, demonstrating feasibility of using thermogravimetric analysis for quantitative purposes.     

Pyrolysis study of Sol-gel derived TiO2 Powders: Part II. TiO2-anatase prepared by reacting titanium(IV) isopropoxide with oxalic acid

Homogeneous TiO₂ powders were obtained, via sol-gel method, hydrolysing titanium(IV) isopropoxide, previously reacted with oxalic acid in order to better control the gelling process. The characterization of the amorphous TiO₂ powders was carried out by using different techniques such as FT-IR, XRD and N2 adsorption analysis. Coupled thermogravimetric (TG) gas chromatographic (GC) and mass spectrometric (MS) analyses were performed to quantify the organic content present in the titania gel and its release during pyrolysis. A detailed semiquantitative analysis of the evolved chemical species from TG-MS data allowed to describe the chemical composition of the TiO₂ gel and the chemical rearrangements occurring in matrix during pyrolysis up to its crystallization to anatase form at 530°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis,thermal characterization,and tensile properties of alipharomatic polyesters derived from 1,3‐propanediol and terephthalic,isophthalic, and 2,6‐naphthalenedicarboxylic acid

In this work, three alipharomatic polyesters—poly(propylene terephthalate) (PPT), poly(propylene isophthalate) (PPI), and poly(propylene naphthalate) (PPN)—were prepared and studied with the aliphatic diol 1,3‐propanediol and the corresponding aromatic diacids. Their synthesis was performed by the two‐stage melt polycondensation method in a glass batch reactor. The thermal characterization of these polyesters was carried out with different thermal techniques such as simultaneous thermogravimetry/differential thermal analysis, thermomechanical analysis (TMA), and dynamic thermomechanical analysis. From the recorded values for the glass‐transition temperature (T_g) and melting temperature with all the aforementioned techniques, it could be said that they were in good agreement. According to the thermogravimetric results, PPT and PPI showed about the same thermal stability, whereas PPN seemed to be somewhere more thermostable. Remarkably, a transition existed immediately after T_g that was realized by the first derivative of TMA, and it was characterized as a midrange transition. For all polyesters, the average coefficient of linear thermal expansion was calculated with TMA. The secondary relaxations T_β and T_γ, recorded with dynamic mechanical thermal analysis, were mainly affected by the kinds of monomers. Concerning the mechanical properties, PPN had the highest tensile strength at break, whereas PPT had the highest elongation at break. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3998–4011, 2005     

Synthesis, crystal structure and thermal decomposition of a new copper propionate [Cu(CH3CH2COO)2]·2H2O

A new copper propionate complex was synthesised and characterized for application as precursor for CuO based oxide thin films deposition. The FT-IR and X-ray diffraction analyses have revealed the formation of a cooper propionate complex [Cu(CH₃CH₂COO)₂]·2H₂O. The crystal and molecular structure of a new copper propionate complex was determined by XRD on the copper propionate single crystal. The copper propionate complex has a binuclear structure, connected by bridging bidentate carboxylates groups and a Cu?Cu bond of 2.6 Å. The thermal decomposition of copper propionate has been investigated by thermal analysis using thermogravimetric (TG) and differential thermal analysis (DTA), differential thermal analysis coupled with quadrupole mass spectrometry-QMS, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) techniques. TG and XRD data indicate the reduction of Cu(II)-Cu(I,0) during the decomposition of copper propionate.     

Preparation,Mechanical Properties and Thermal Degradation Kinetics of a Novel Poly(ester-ether-imide) Elastomer Based on N′,N-Bis(2-hydroxyethyl)-Pyromellitimide Unit

A novel poly(ester-ether-imide) (PEEI) based on N′,N-bis(2-hydroxyethyl)-pyromellitimide unit was synthesized via a conventional two-stage procedure with 1,4-butanediol (BD), dimethyl terephthalate (DMT) and poly(tetramethylene glycol) (PTMG1000). The structures of imide dihydric alcohol and PEEI were confirmed by FT-IR and ¹H-NMR spectra, respectively. The thermal properties and mechanical properties were investigated. The results show PEEI possesses good mechanical properties and excellent thermal stability with the 5% weight loss temperature of the PEEI at 367.3°C, and melting temperature of hard segments (T_mh) at 209.7°C. In addition, the kinetic parameters of thermal degradation of the PEEI were studied by thermogravimetric analysis (TGA) at different heating rates. The activation energy of the solid-state process was determined to be 174.83 and 175.83 kJ/mol using Kissinger and Flynn–Wall–Ozawa methods, respectively. The degradation mechanism model of PEEI was determined bythe Coats-Redfern method. Compared with the values obtained from the Kissinger and Flynn–Wall–Ozawa methods, the actual reaction mechanism of the novel PEEI is a F₁ type (Random nucleation with one nucleus on the individual particle nucleation) and growth model with integral g(a)=?ln(1?a)).     

An iron (II) guanidinate compound: Synthesis,characterization, thermal properties and its application as a CVD precursor for iron oxide film

An iron compound containing guanidinate ligand [Fe((SiMe₃)₂NC(ⁱPrN)₂)₂] was synthesized using a conventional lithium‐salt‐elimination reaction, and its chemical structure was characterized through elemental analysis, ¹H‐NMR and single‐crystal X‐ray diffraction, respectively. The thermal properties of the compound were examined through thermogravimetric analysis (TGA), and the TGA results demonstrated that the compound possessed sufficient volatility and suitable thermal stability for the CVD process. Moreover, the deposition experiments were conducted using the synthesized compound as a precursor and O₂ as an oxygen source to confirm its applicability as a CVD precursor, and α‐Fe₂O₃ films were successfully deposited at a relatively low deposition temperature (300°C).     

CdTe@Cu(OH)2 nanocomposite: Aqueous synthesis and characterization

CdTe@Cu(OH)₂ nanocomposites were synthesized in aqueous solution by a seed-mediated growth approach. The effect of refluxing time and the concentration of Cu²⁺ on the preparation of these samples were measured using UV-visible absorption and photoluminescence analysis. The emission peak of the synthesized nanocomposites (CdTe@Cu(OH)₂) was shifted from 605 (CdTe seed) to 621 nm. The size of CdTe nanoparticles were averaged about 3.22 nm, and the CdTe@Cu(OH)₂ nanocomposites were averaged as 5.19 nm. The synthesized CdTe@Cu(OH)₂ nanocomposite were characterized with XRD, EDAX, TEM, FT-IR, EPR, and thermal analysis (TG/DTG curves). The results indicate that as-prepared nanoparticles with core/shell structure exhibit interesting optical properties.     

Synthesis,characterization and DFT aspects of some oxovanadium(IV) and manganese(II) complexes involving dehydroacetic acid and β-diketones

Six new mixed-ligand oxovanadium(IV) and manganese(II) complexes of the general composition [VO(dhaH)(L¹H)(L²)] and [Mn(dhaH)(L¹H)(L²)], where dhaH=dehydroacetic acid, L¹H=β-ketoenolates viz., acetoacetanilide (aaaH), o-acetoacetotoluidide (o-aatdH), o-acetoacetanisidide (o-aansH) and L²=benzimidazole (bzl), 3-methyl-1phenyl-2pyrazoline-5one (mphp), 2-aminobenzimidazole (abzl) or 2-aminobenzathiozole (abtz) have been synthesized. The resultant complexes were characterized on the basis of elemental analysis, molar conductance, magnetic measurements, mass spectrometry, thermogravimetric analysis, infrared and electron spin resonance studies. The thermal decomposition processes of one representative of the complexes are discussed and the order of reaction (n), the activation energies (E_a), the pre-exponential factor (A), have been calculated from thermogravimetric (TG) and differential thermogravimetric (DTG) curves. Gaussian 09 software package was used to carry out theoretical computation using density functional theory (DFT) methods with Becke3-Lee-Yang-Parr (B3LYP) hybrid exchange-correlation functional and the standard LANL2 MB basis set. Based on combined experimental-theoretical characterization, a suitable octahedral structure has been proposed for this class of complexes.     

Thermal and photoluminescence properties of hydrated YPO4:Eu nanowires

In this work, we used the solution precipitation route to synthesize Eu³⁺-doped YPO₄·nH₂O nanowires. The structure, morphology, composition, thermal behavior, and photoluminescence of as-synthesized product were characterized by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopic (FE-SEM) and photoluminescence (PL) spectra. The dependence of the structure, morphology, composition and luminescent properties on the thermal treatment was investigated. The results indicate that the aqueous synthesis has a better control on the structure, morphology, composition of the products, and that the heat treatment induces the transitions of the structure, composition, and luminescent properties.     

Researches on Thermal Decomposition Kinetics of Composite Modified Double-base Propellants

The thermal decomposition kinetics of composite modified double‐base (CMDB) propellants with a series of contents of hexogeon (RDX) was investigated by using parameters of T_eo, T_i, T_p, T_f, T_b, T_a, E, lg A and ΔH, which were obtained from using a CDR‐4P differential scanning calorimeter (DSC) and Perkin‐Elmer Pyris 1 thermogravimetric analyzer (TG) analyses with heating rates of 5, 10, 15 and 20 K/min. Reliable activation energy was calculated using Flynn‐Wall‐Ozawa method before analyzing the thermal decomposition mechanism. TG‐DTG curves were treated with Malek method in order to obtain the reaction mechanisms. The obtained results show that the thermal decomposition mechanisms with the conversion from 0.2 to 0.4 was f(α)?1/2α, and with the conversion from 0.5 to 0.7 was f(α)?(1/4)(1?α)[?ln(1?α)]^?3.