Thermal degradation behaviour of some metal chelate polymer compounds with bis(bidentate) ligand by TG/DTG/DTA

Seven novel divalent transitional metal chelate polymers compounds (commonly known as chelate compounds or metal coordination complexes or polymer complexes) have been characterized by thermogravimetry (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA) methods. Thermal decomposition behaviour of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) polymers with terphthaoyl-bis(p-methoxyphenylcarbamide) has been investigated by thermogravimetric analysis (TGA) at heating rate 10 °C min^?1 under nitrogen atmosphere. TG/DTA of chelate compounds were shown to be a stable compound against thermal decomposition which was measured on the basis of final decomposing temperature, but it is observed in some curves that decomposition takes place at low temperature due to the lattice water, which is always placed at outer coordination sphere of the central metal ion. The presence of both lattice and coordinated water were noteworthy investigated in Co(II), Ni(II) and Cu(II) chelate polymer compounds, whereas lattice water found in Zn(II), Cd(II) and Hg(II). However, Mn(II) showed only coordinated water. Thermal stabilities for release of lattice water, coordinated water and organic moiety that occur in sequential decomposition of chelate compounds are explained on the basis of ionic size effect and electronegativity. The processes of thermal degradation taking place in seven chelate polymers were studied comparatively by TG/DTG/DTA curves which indicating the difference in the thermal decomposition. Coats–Redfern integral method is used to determine the kinetic parameters for the successive steps in the decomposition sequence of TG curves. Scanning electron microscope images of some chelate polymers were shown in previous publication revealed that particle sizes of chelate polymers were found to be of nanomaterial level therefore, resulting chelate compounds might be called as nanomaterial.     

Thermal decomposition of polymeric materials: Characteristics of kinetics at non-isothermal heating

General conclusions are made based on the results of experimental and theoretical investigations of the decomposition kinetics of various polymeric materials in a wide range of heating rates. It was found that the decomposition process of the investigated materials proceeds within confined temperature intervals. Kinetic equations are suggested to describe the thermal decomposition processes of polymers and natural coals, based on the characteristic revealed.     

The thermal decomposition of the 2-methyl-8-quinolinol (8-hydroxyquinaldine) chelates of scandium,thorium, uranium (VI) and the rare earth elements

The thermal decomposition of the 2-methyl-8-quinolinol (8-hydroxyquinaldine) chelates of scandium, thorium, uranium(VI), yttrium and the rare earth elements was studied on the thermobalance. It was found that the scandium and uraniurn(VI) chelates can lose the extra molecule of solvation by thermal decomposition. The thorium chelate was found to be the most stable of all the chelates studied. The temperature limits for the chelates and the minimum oxide level temperatures are given.     

Vinyl Polymerization of Ethyl Acrylate Initiated by TI3+-Ascorbic Acid Redox System

The application of polymers at ever-increasing temperatures has given impetus to research on the chemistry of thermal decomposition. In recent years polymers have been used for a variety of high-temperature applications, such as cooking vessels, motor insulation, and re-entry vehicle heat shields. Interest in chemistry of decomposition has been found in such industries as tobacco and grinding-wheels. Because of the vast number of polymers that are available and the variety of applications thousands of papers have appeared in the literature. Rather than give a complete review the purpose of this paper is to give a brief survey of topics that have been emphasized in the author's research, namely kinetics, mechanisms, and gaseous decomposition products at elevated temperatures.     

NEW POLY(METHACRYLATE)S CONTAINING OXIME ESTERS MOIETIES BASED ON CYCLOHEXANON AND CYCLOPENTANON

The synthesis of two new methacrylates such as 2-[(cyclohexylideneamino)oxy]-2-oxoethyl methylacrylate (CHOEMA)and 2-[(cyclopentylideneamino)oxy]-2-oxoethyl methylacrylate(CPOEMA)are described.The monomers produced from the reaction of corresponding cyclohexanone O-(2-chloroacetyl)oxime and cyclopentanone O-(2- chloroacetyl)oxime with sodium methacrylate was polymerized in 1,4-dioxane solution at 65℃using AIBN as an initiator. The monomers and their polymers were characterized by IR,~1H- and ~(13)C-NMR s...     

Kinetics of bulk azide/alkyne “click” polymerization

A bulk step‐growth polymerization of multifunctional azides and alkynes through the copper (I)‐catalyzed azide‐alkyne cycloaddition (CuAAC) reaction is described. The polymerization kinetics of two systems containing different diynes, bisphenol E diyne (BE‐diyne)/bisphenol A bisazide (BA‐bisazide) and tetraethylene glycol diyne (TeEG‐diyne)/BA‐bisazide, are evaluated by differential scanning calorimetry (DSC), shear rheology, and thermogravimetric analysis. The effects of catalyst concentration on reaction kinetics are investigated in detail, as are the thermal properties (glass transition and decomposition temperatures) of the formed polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4093–4102, 2010     

Thermal decomposition kinetics of some transition metal coordination polymers of fumaroyl bis (paramethoxyphenylcarbamide) using DTG/DTA techniques

In the present work, thermal degradation behaviors of the Zn (II), Cd(II), and Hg(II) coordination polymers of fumaroyl bis (paramethoxyphenylcarbamide) (fbpmpc) have been investigated by using thermogravimetric (TG) analysis, differential thermal analysis (DTA) and derivative thermogravimetry (DTG) analysis under non-isothermal conditions in nitrogen atmosphere at multiple heating rates. TG–DTA study noteworthy inferred the presence of lattice water in outer sphere of all the polymers. The decomposition was carried out in three-four well-separated stages where involved the loss of water molecules in the first step followed by organic ligand. Furthermore, the kinetics and thermodynamic stabilities of multi-steps thermal degradation were evaluated. The activation energy (E_a), order of reaction (n), Arrhenius factor (A), enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG) of coordination polymers were obtained by using the Coats–Redfern (CR) method. Ultimately, based on initial, half and final decomposition temperature, and kinetics parameters values the orders of thermal stability were estimated.     

Synthesis and Characterization of Pr（DPM）3 Served as Precursor for MOCVD

Praseodymium β-diketone chelate, Pr(DPM)3 [DPM=2,2,6,6-tetramethyl-3,5-heptanedionato], was successfully synthesized from the inorganic salt praseodymium chloride and HDPM(2,2,6,6-tetramethyl-3,5-heptane-dione) in an ethanol/aqueous solution followed distillation at low pressure and recrystallization from toluene. The physical and thermal properties of the chelate, including volatility, stability, and thermal decomposition, were investigated by elemental analyses, 1H NMR spectroscopy, XRD, TG/DTG/DTA analysis, infrared spectroscopy, and mass spectroscopy. The chelate with high purity prepared by thes of this study also shows sufficient volatility and stability in inert gases, which could be used as the precursor for metal-organic chemical vapor deposition(MOCVD).     

Mechanisms and kinetics of thermal decomposition of plastics from isothermal and dynamic measurements

The kinetics of decomposition of plastics are of interest from different points of view, i.e. evolution of harmful substances during fires or waste incineration, recovering of chemical raw materials from plastic refuses and designing of recycling procedures. To measure the formal kinetic parameters of the degradation of polymers isothermal and dynamic methods are applied in this work. Dynamic measurements are performed by combined thermogravimetry mass spectrometry (TG-MS), the isothermal measurements are carried out with a new closed loop-type reactor. To evaluate consistent kinetic data from isothermal and dynamic measurements, the energy balance for the sample in dynamic measurements has to be considered to obtain the true sample temperature and heating rate. Subject of this investigation is the exploitation of dynamic and isothermal methods for measuring and interpreting the kinetics of thermal decomposition of plastics. Results for commodity plastics polyethylene and poly(vinyl chloride) (PVC) are presented. The combined application of TG–MS, isothermal experiments in the closed loop-type reactor and DSC leads to new results for the decomposition kinetics of PVC. The dehydrochlorination mechanism at moderate temperature can be distinguished in an endothermal and exothermal part. The benzene formation is identified as a second order reaction. A great advantage of the isothermal method is, that changes in the mechanisms are detectable, i.e. changes in the apparent order of the reaction and the apparent activation energy. From that, new mechanistic aspects of the decomposition kinetics of polyethylene were obtained.     

A thermal decomposition study of polymers by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

The thermal decomposition of polymers (poly(vinyl chloride) (PVC) and polystyrene (PS)) has been studied with synchrotron VUV photoionization mass spectrometry at low pressure. Pyrolysis products formed at different temperatures have been identified by the measurement of photoionization mass spectra at different photon energies. The experimental results demonstrate the variation of the pyrolysis product pool of PVC at different temperatures, dividing the thermal decomposition process into two stages: the low‐temperature stage to form HCl and benzene, and the high‐temperature stage to form numerous large aromatic hydrocarbons. For the thermal decomposition of PS, four reaction categories are determined. This work reports a new application of synchrotron VUV photoionization mass spectrometry in the study of the thermal decomposition of polymers, and demonstrates its good performance in product analysis, which is expected to help understand the thermal decomposition mechanism of PVC, PS and other synthesized polymers. Copyright © 2009 John Wiley & Sons, Ltd.     

Eco-friendly fast synthesis and thermal degradation of optically active polyamides under microwave accelerating conditions

<正>An optically active bulky aromatic diacid chiral monomer,(2S)-4-[(4-methyl-2-phthalimidylpentanoyl-amino) benzoylamino]isophthalic acid(1),containing a rigid phthalimide and flexible L-leucine pendent group was synthesized in five steps.A fast and clean method for direct polyamidation reaction of monomer 1 with various aromatic diamines under microwave irradiation and conventional heating was performed.The polymerization reactions provided optically active polyamides with high yields and inherent viscosities in the range of 0.36-0.74 dL/g.Their thermal properties were evaluated by thermogravimetric analysis(TGA) and differential scanning calorimetry.TGA thermograms show that the polymers are thermally stable,10%weight loss temperatures are in excess of 385℃,and char yields at 800℃are higher than 56%.The data obtained from TGA were used to study the kinetics of thermal decomposition of the resulting polymers. The interpretation of kinetic parameters(E,ΔH,ΔS andΔG) of thermal decomposition stages was evaluated using Coats and Redfern equation.     

Synthesis of highly branched polymers via three-dimensional radical polymerization in the presence of oxygen

It is shown that branched and highly branched vinyl polymers can be prepared by three-dimensional radical polymerization in the presence of dissolved oxygen, as exemplified by the oxidative copolymerization of styrene and divinylbenzene. The conditions of synthesis of highly branched polymers with a high yield??the ratio between monovinyl and divinyl comonomers and the rate of oxygen bubbling??are determined. The kinetics of formation of branched polystyrenes and the features of their molecular-mass distribution are studied. Elemental-analysis data show that the polymeric product contains 22?C24 wt % oxygen, which, according to the IR data, enters into the composition of carbonyl, hydroxyl, and peroxide groups. The thermal decomposition of polymeric products is investigated via the TGA-DSC method. The main exothermal peak at ??145°C is associated with the decomposition of peroxide groups, which is accompanied by the evolution of formaldehyde.     

Effects of N-methyl substitution on the thermal stability of polyurethanes and polyureas

Thermogravimetric studies on a series of structurally related polyurethanes and polyureas are reported. The thermal stabilities of N-methylsubstituted polymers are sensibly higher than those of the corresponding unsubstituted (N-H) polymers. Based on a knowledge of the primary thermal fragmentation processes in these polymers, an attempt has been made to correlate chemical structure, mechanism of thermal decomposition and thermal stability.     

Effect of matrix components on chromium atomization processes in graphite furnace atomic absorption spectrometry

The effect of various organic and inorganic matrix components on chromium atomization in graphite furnace atomic absorption spectrometry is studied. The results are explained on the basis of chromium's atomization mechanisms. The two predominant mechanisms are the thermal dissociation of the oxide and of the carbide. Losses through molecular volatilization reduce the sensitivity when chromium chelate complexes are atomized. In this case, the atomization mechanism consists of the thermal dissociation of the chelate. The formation of chromium carbide from the carbon residue produced by decomposition of the organic solvents leads to a loss of sensitivity.     

Study Kinetics of Thermal Decomposition and Electrochemical Oxidation by Using Nanocomposite Paste of Novel Poly(amide-ether)s Derived from Asymmetric Diamine

A new asymmetric diamine containing diarylimodazole pendant was synthesized from the nucleophilic substitution reaction of 1-fluoro-4-nitrobenzene and 2,4-dihydroxy benzaldehyde in the presence of K₂CO₃, followed by reaction with benzil and ammonium acetate for the preparation of imidazole ring. This novel diamine was used to prepare poly(amide-ether) (PAE) in reaction with different commercially available dicarboxylic acids via direct polycondensation using triphenyl phosphite and pyridine (Py) as catalyst. The PAEs were fully characterized and their properties such as inherent viscosity, solubility, optical, thermal and kinetics of thermal decomposition, and electrochemical oxidation were investigated. The polymers had inherent viscosity in the range of 0.47–0.65 dL/g and were noncrystalline with excellent solubility in various polar aprotic organic solvents. Their T_g values ranged from 200 to 355°C and 10% weight loss temperature above 450°C in nitrogen and left more than 70% residue at 650°C. The kinetic parameters of thermal degradation such as activation energy, entropy, enthalpy and Gibbs free energy of thermal decomposition have been evaluated using different equations. We also report electrochemical oxidation of the resulting polymers in aqueous solution by using cyclic voltammetry technique on the multi-walled carbon nanotube-modified glassy carbon electrode.     

Physicochemical Properties of Polyazomethine Polymers

Polyazomethine chelate polymers of 3d transition metal ions have been prepared and characterized in terms of elemental analysis, magnetic moment, electronic spectra, infrared spectra, and thermal and electrical properties. All the polymers exhibit 1:1 stoichiometry and are insoluble in common organic solvents.     

Thermal, spectroscopic, and solvent influence studies on mixed-ligand copper(II) complexes containing the bulky ligand: Bis[N-(p-tolyl)imino]acenaphthene

Four mixed-ligand copper(II) complexes containing the rigid bidentate nitrogen ligand bis[N-(p-tolyl)imino]acenaphthene (abb. p-Tol-BIAN) ligand are reported. These complexes, namely [Cu(p-Tol-BIAN)(2)](ClO(4))(2)1, [Cu(p-Tol-BIAN)(acac)](ClO(4)) 2, [Cu(p-Tol-BIAN)Cl(2)] 3 and [Cu(p-Tol-BIAN)(AcOH)(2)](ClO(4))(2)4 (where acac, acetylacetonate and AcOH, acetic acid) have been prepared and characterized by elemental analysis, spectroscopic, magnetic and molar conductance measurements. ESR spectra suggest a square planar geometry for complexes 1 and 2. In complexes 3 and 4, a distorted tetrahedral arrangement around copper(II) centre was suggested. Solvatochromic behavior of all studied complexes indicates strong solvatochromism of their solutions. The observed solvatochromism is mainly due to the solute-solvent interaction between the chelate cation and the solvent molecules. Thermal properties and decomposition kinetics of all complexes are investigated. The kinetic parameters (E, A, Delta H, Delta S and Delta G) of all thermal decomposition stages have been calculated using the Coats-Redfern and other standard equations.     

Thermal decomposition of hexamminecobalt(III) chloride

The results of comparative thermal analysis (TG-DTG-DTA-DSC) of the thermal decomposition of hexamminecobalt(III) chloride in air atmosphere are reported. The kinetics and mechanism of the thermal decomposition, the process enthalpy and the variation in specific thermal capacity of the solid product reaction with temperature were determined.     

A comprehensive assessment on degradation of multi-walled carbon nanotube-reinforced EMA nanocomposites

Thermal degradation kinetics of MWNT-reinforced EMA-based nanocomposites having different methyl acrylate (MA) contents (by % mass) ranging from 9 to 30% have been monitored. Kissinger and Flynn?CWall?COzawa methods for evaluating non-isothermal degradation of polymers have been examined. Overall, the thermal stabilities of the nanocomposites are the function of amount of MWNTs loading and their state of dispersion that depends on the MA content of respective EMAs. Composite samples exhibit higher activation energy (E _a) than the neat EMAs but the E _as of the composites diminish with increased MA contents of the matrices. TG-Mass spectrometry has been used to identify the volatile products resulting from thermal degradation of composites, and a promising mechanism has been proposed over different range of temperatures of degradation. It is proposed that the side-group scission of methoxycarbonyl group initiates thermal decomposition following combination of chain end and random chain scission reactions, ensuing pseudo second-order kinetics.     

Comparative Thermogravimetric Studies of Poly(ether-ketone/sulfone) Imides and Their Parent Polymers: I. Poly(ether-ketone/sulfone) ethylimide

Thermogravimetry (TG) was employed to study the thermal degradation kinetics of poly(etherketone/sulfone)ethylimide (PEK-IE and PES-IE). The corresponding decomposition activation energies and reaction orders were obtained and the comparison was made with their parent polymerspoly(ether-ketone/sulfone) with Cardo group (PEK-C and PES-C). The results show that the degradation activation energies of PEK-IE and PES-IE were lower than that of PEK-C and PES-C; and two stages of the degradation process were found for all the four polymers. For PEK-IE and PES-IE, the activation energies in the first decomposition stage are much lower than that in the second stage and the two stages can be taken as slow induction and fast degradation, whereas for PEK-C and PES-C the activation energies in the first decomposition stage are larger than that in the second stage, and the two stages can both be taken as two fast degradation stages. The decomposition mechanism of the two stages was also speculated.This revised version was published online in November 2005 with corrections to the Cover Date.