Ethylbenzene solubility,diffusivity, and permeability in poly(dimethylsiloxane)

The pure‐gas sorption, diffusion, and permeation properties of ethylbenzene in poly(dimethylsiloxane) (PDMS) are reported at 35, 45, and 55 °C and at pressures ranging from 0 to 4.4 cmHg. Additionally, mixed‐gas ethylbenzene/N₂ permeability properties at 35 °C, a total feed pressure of 10 atm, and a permeate pressure of 1 atm are reported. Ethylbenzene solubility increases with increasing penetrant relative pressure and can be described by the Flory–Rehner model with an interaction parameter of 0.24 ± 0.02. At a fixed relative pressure, ethylbenzene solubility decreases with increasing temperature, and the enthalpy of sorption is −41.4 ± 0.3 kJ/mol, which is independent of ethylbenzene concentration and essentially equal to the enthalpy of condensation of pure ethylbenzene. Ethylbenzene diffusion coefficients decrease with increasing concentration at 35 °C. The activation energy of ethylbenzene diffusion in PDMS at infinite dilution is 49 ± 6 kJ/mol. The ethylbenzene activation energies of permeation decrease from near 0 to −34 ± 7 kJ/mol as concentration increases, whereas the activation energy of permeation for pure N₂ is 8 ± 2 kJ/mol. At 35 °C, ethylbenzene and N₂ permeability coefficients determined from pure‐gas permeation experiments are similar to those obtained from mixed‐gas permeation experiments, and ethylbenzene/N₂ selectivity values as high as 800 were observed. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1461–1473, 2000     

Effect of organic and inorganic compounds on dissolution kinetics of chalcopyrite in hydrogen peroxide– Hydrochloric acid system

The addition of 2-Propanol as an organic substance and NaCl as an inorganic compound in hydrochloric acid with hydrogen peroxide as a strong leaching agent of chalcopyrite was investigated. The effects of the leaching parameters on copper extraction, such as stirring speed, H₂O₂ concentration, temperature, HCl concentration and solid/liquid ratio were studied. The maximum final copper extraction of 54.55% was obtained with 600 rpm stirring speed, 1.5 M H₂O₂, 0.5 M HCl, 600 rpm, 50 °C, 240 min of the reaction and particle size of ?106 +75 µm. Further experiments were performed when the solid-to-liquid ratio (S/L), stirring speed, temperature, HCl, H₂O₂ and leaching time were kept constant to examine the influence of NaCl and 2-Propanol concentrations in the range of 0–0.5 M and 0–3 M, respectively. The results showed that the copper extraction was increased up to 58.11% with addition of NaCl. While copper extraction yield reached 94.25% in case of addition of 2-propanol with the optimum parameters(0.5 M HCl,50 °C, 1.5 M H₂O₂, 600 rpm, particle size ?106 +75 μm, solid liquid ratio 2g/L, 3 M 2-propanol). The chalcopyrite leaching in hydrogen peroxide– hydrochloric acid system was found to be described by the interface transfer and diffusion across the product layer with activation energy of 77.14 kJ/mol. Addition of 2-propanol suggested that the reaction was under product layer diffusion control and decreased the activation energy of chalcopyrite leaching to 67.98 kJ/mol.     

Sorption,diffusion, and permeation of ethylbenzene in poly(1‐trimethylsilyl‐1‐propyne)

The solubility, diffusivity, and permeability of ethylbenzene in poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) at 35, 45 and 55 °C were determined using kinetic gravimetric sorption and pure gas permeation methods. Ethylbenzene solubility in PTMSP was well described by the generalized dual‐mode model with χ = 0.39 ± 0.02, b = 15 ± 1, and C^′_H = 45 ± 4 cm³ (STP)/cm³ PTMSP at 35 °C. Ethylbenzene solubility increased with decreasing temperature; the enthalpy of sorption at infinite dilution was −40 ± 7 kJ/mol and was essentially equal to the enthalpy change upon condensation of pure ethylbenzene. The diffusion coefficient of ethylbenzene in PTMSP decreased with increasing concentration and decreasing temperature. Activation energies of diffusion were very low at infinite dilution and increased with increasing concentration to a maximum value of 50 ± 10 kJ/mol at the highest concentration explored. PTMSP permeability to ethylbenzene decreased with increasing concentration. The permeability estimated from solubility and diffusivity data obtained by kinetic gravimetric sorption was in good agreement with permeability determined from direct permeation experiments. Permeability after exposure to a high ethylbenzene partial pressure was significantly higher than that observed before the sample was exposed to a higher partial pressure of ethylbenzene. Nitrogen permeability coefficients were also determined from pure gas experiments. Nitrogen and ethylbenzene permeability coefficients increased with decreasing temperature, and infinite dilution activation energies of permeation for N₂ and ethylbenzene were −5.5 ± 0.5 kJ/mol and −74 ± 11 kJ/mol, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1078–1089, 2000     

The solubility and diffusion of water in poly(aryl-ether-ether-ketone) (PEEK)

The transport properties of water in neat poly(aryl-ether-ether-ketone) (PEEK) coupons (2 to 6 mm thick) were investigated by gravimetric and mass spectrometric methods. The solubility of water increases from 0.44 wt.% at 35°C to 0.55 wt.% at 95°C; the temperature coefficient is 8 kJ/mol (1.9 kcal/mol). The diffusion processes for sorption, desorption, and resorption at 35°, 50°, 65°, 80°, and 95°C are, within experimental error, the same. The activation energy for diffusion is 42.7 kJ/mol (10.2 kcal/mol). The diffusion process is classical Case I Fickian in the temperature region investigated.     

Thermally induced polymerization of isobutylene in the presence of SnCl4: Kinetic study of the polymerization and NMR structural investigation of low molecular weight products

The polymerization reactivity of isobutylene/SnCl₄ mixtures in the absence of polar solvent, was investigated in a temperature interval from −78 to 60 °C. The mixture is nonreactive below −20 °C but slow polymerization proceeds from −20 to 20 °C with the initial rate r₀ of the order 10⁻⁵ mol · l⁻¹ · s⁻¹. The rate of the process increases with increasing temperature up to ∼10⁻² mol · l⁻¹ · s⁻¹ at 60 °C. Logarithmic plots of r₀ and M̄_n versus 1/T exhibit a break in the range from 20 to 35 °C. Activation energy is positive with values E = 21.7 ± 4.2 kJ/mol in the temperature interval from −20 to 35 °C and E = 159.5 ± 4.2 kJ/mol in the interval from 35 to 60 °C. The values of activation enthalpy difference of molecular weights in these temperature intervals are ΔH_Mn = −12.7 ± 4.2 kJ/mol and −38.3 ± 4.2 kJ/mol, respectively. The polymerization proceeds quantitatively, the molecular weights of products are relatively high, M̄_n = 1500–2500 at 35 °C and about 600 at 60 °C. It is assumed that initiation proceeds via [isobutylene · SnCl₄] charge transfer complex which is thermally excited and gives isobutylene radical‐cations. Oxygen inhibits the polymerization from −20 to 20 °C. Possible role of traces of water at temperatures above 20 °C is discussed. It was verified by NMR analysis that only low molecular weight polyisobutylenes are formed with high contents of exo‐ terminal unsaturated structures. In addition to standard unsaturated groups, new structures were detected in the products. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1568–1579, 2000     

Electrolytic molybdenum sulfides for thin-layer lithium power sources

The active molybdenum sulfide compound Mo₂S₃, which should be considered as a cathode material for thin-layer rechargeable power source, has been produced by electrolysis. Using impedance spectroscopy and potential relaxation method after current interruption, the kinetic parameters of lithium intercalation in electrolytic Mo₂S₃ have been obtained. Activation energy of Li⁺ migration in electrolyte (13.76 kJ/mol), charge transfer through the Mo₂S₃ electrode/electrolyte interface (38.8 kJ/mol), and Li⁺ diffusion in a solid phase (57.3 kJ/mol) have also been established. Taking into account the coefficient data of charge mass transfer in a solid phase and the reaction rate coefficient of charge transfer through the interface electrode/electrolyte within the temperature range 20–50 °C, the stage of Li⁺ transfer in a solid phase has been determined as a limiting stage for lithium intercalation in electrolytic molybdenum sulfide Mo₂S₃.     

Sodium Chloride-Induced Modulation of the Activity and Thermal Stability of Short-Chain Oxidoreductase from the Archaeon Thermococcus sibiricus

Recently, we have studied properties and structural features of the thermostable halotolerant alcohol dehydrogenase from archaeon Thermococcus sibiricus (TsAdh319). In the present work, the effect of sodium chloride on activity and thermostability was explored using circular dichroism, fluorescent spectroscopy, and differential scanning calorimetry. The activity of TsAdh319 increased in the presence of NaCl and remained at the elevated level up to 4 M of NaCl. Sodium chloride at molar concentrations reduced the optimal reaction temperature, increased both Michaelis constant (K _m) and k _cat values for the substrates tested, decreased affinity for the coenzyme, and stoichiometry of coenzyme binding. No changes were revealed in a secondary or quaternary structure of the protein in the presence of NaCl up to 90 °C. According to differential scanning calorimetry, the irreversible unfolding started around 90 °C, the addition of NaCl decreased T _m from 104.2 to 102.2 °C, and reduced ΔH from 438 to 348 kJ/mol. Kinetic studies revealed positive effect of NaCl on the TsAdh319 thermostability. The results are interpreted in regard to TsAdh319 structural data.     

Kinetics of low temperature CO oxidation over Pt/SnO2 catalyst

In a CO−O₂ stoichiometric mixture, the kinetic parameters, reaction order, rate constant and activation energy of CO oxidation over a Pt/SnO₂ catalyst have been measured using a fixed bed flow reactor near 0°C. The results show that it is a first-order reaction. The activation energy of CO oxidation over Pt/SnO₂ prepared with SnO₂ calcined at 300°C was approximately 21 kJ/mol. The activation energy of CO oxidation over Pt/SnO₂ changed slowly with SnO₂ calcination temperature above 400°C, and reached approximately 45 kJ/mol.     

The Thermodynamic Characteristics of Sublimation of Aluminum and Indium Complexes with Tetraphenylporphin according to the High-Temperature Mass Spectrometry Data

The thermodynamic characteristics of vaporization of meso-tetraphenylporphin complexes (X)MTPP (M = Al, In; X = Cl, OH; TPP is the meso-tetraphenylporphin H₂TPP dianion) were studied by the Knudsen effusion method with mass spectrometric control of vapor composition. Chloride complexes sublimed as monomers over the temperature range 480–590 K. The hydroxo complex of aluminotetraphenylporphin was transferred into the gas phase in the form of the μ-oxo dimer. The temperature dependences of saturated vapor pressure were used to determine the enthalpies of sublimation of metalloporphyrins, which were found to be 203 ± 3.5 and 207 ± 6 kJ/mol for the chloride complexes of In and Al, respectively, and 206 ± 8 and 406 ± 40 kJ/mol for the monomer and μ-oxo dimer of (hydroxy)aluminum(III)porphyrin, respectively. The thermodynamic parameters of vaporization and the melting point of (OH)AlTPP were also determined (Δ_vapH° = 116 ± 6 kJ/mol, Δ_apS° = 72 ± 11 J/(mol K), and T_m = 579 K). Composition-thermodynamic property correlations were analyzed for metalloporphyrins.     

A Novel Process for CO2 Capture by Using Sodium Metaborate,Part II: Carbonation Reaction and Kinetic Studies

In Part II of this two‐part series of papers, optimization of carbonation reaction with sodium metaborate and kinetics of the reaction are studied and compared to the structural properties, which were reported in Part I. This paper presents a comprehensive study on the optimization of reaction conditions and determination of reaction parameters of sodium metaborate (NaBO₂) and carbon dioxide (CO₂). Both hydrated and dehydrated forms of NaBO₂ have high sorption capacities of CO₂ up to 400°C. Decomposition of the products starts beyond 400°C and completes at 600°C. The shrinking core model is used to explain the kinetics of the noncatalytic heterogeneous reaction. The reaction progresses in two stages: one is surface reaction controlled and the other is diffusion controlled. The apparent activation energy and preexponential factor for reaction‐controlled and diffusion‐controlled regions are calculated as 11.8 kJ/mol and 3.5 × 10⁶ cm²/min and 18.2 kJ/mol and 6.5 × 10⁻⁵ cm²/min, respectively.     

Kinetic behavior of ethylene/1‐hexene copolymerization in slurry and solution reactors

The copolymerization of ethylene and 1‐hexene over a spherical polymer/MgCl₂‐supported TiCl₄ catalyst was studied as a function of the polymerization temperature from 40 to 100 °C in a slurry reactor and from 120 to 200 °C in a solution reactor with triethylaluminum (TEA) as a cocatalyst (1.0–6.8 mmol). The activities increased from 40 to 80 °C and then declined monotonically with increases in the temperature during the slurry and solution polymerizations. The kinetic behavior in the slurry and solution operations was described by the same rate expression. The modeling results indicated that the catalyst had at least two different types of catalytic sites; one site was responsible for the acceleration–decay nature of the activity profiles, whereas the second site resulted in long‐term activity. The apparent activation energy for site activation in the slurry operation was 69.9 kJ/mol; no activation energies for site activation could be estimated for the solution operation because the activation process was essentially instantaneous at the higher temperatures. The activation energies for deactivation were 100.3 kJ/mol for the slurry operation and 31.2 kJ/mol for the solution operation. The responses to TEA were similar for the slurry and solution operations; the rates increased with increasing amounts of TEA between 1.0 and 3.4 mmol and then decreased with larger amounts of TEA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2248–2257, 2005     

Electro-desalination of saline solutions by multiwall carbon nanotube electrodes

Electrodes of multiwall carbon nanotube (MWCNT) with polytetrafluoroethylene (PTFE) binding were prepared for NaCl removal from water in the electrosorption system. SEM, XRD and BET analysis were used to characterize the prepared electrodes. The optimum electrosorption parameters (electrosorption temperature, NaCl concentration, electrosorption time, and potential) were studied. The maximum electrosorption capacity (15.64 mg/g) was obtained at −1.0 V, 100 min, and 30 °C. The electrosorption capacity of electrodes decreased from 15.64 mg/g to 6.15 mg/g with the temperature rise from 30 to 50 °C. Also, the kinetics of electrosorption NaCl by Electrodes was investigated by pseudo-first-order and pseudo-second-order. The results indicated that the electrosorption data will fit with the pseudo-first-order model indicating the physio-electrosorption of NaCl by Electrodes with activation energy was 19.45 kJ mol⁻¹. The regeneration result indicated the exceptional and stable reusability of MWCNT/PTFE in the NaCl electrosorption system.     

Phase Transitions of MBBA Confined in Porous Solids

The diffusive and dynamic mechanical behaviour of an epoxy system containing tetraglycidyl-4,4′-diaminodiphenylmethane and a multifunctional Novolac glycidyl ether cured with 4,4′-diaminodiphenylsulfone was studied after water sorption. The diffusion of water was performed at 100% relative humidity, by immersion of specimens in water at 20, 40, 70 and 100°C. In all sorption experiments, the water diffusion followed Fick's law. Diffusion coefficients and saturated water concentrations were estimated for these temperatures. The activation energy for diffusion was determined from the relationship linking the diffusion coefficient and the reciprocal of the absolute temperature. The value obtained was 45.7 kJ mol^-1. Dynamic mechanical analysis of samples immersed in water at 25 and 100°C, and with various water contents, showed a shift in T_g> (defined by the tanδ peak) to lower temperatures over the glass transition region, and a slight decrease in the dynamic storage modulus in the presence of water as a result of a plasticization effect. This revised version was published online in July 2006 with corrections to the Cover Date.     

New approach for synthesis of poly(ethylglyoxylate) using Maghnite-H+, an Algerian proton exchanged montmorillonite clay,as an eco-catalyst

In this works, we have explored a new method for a green synthesis of poly(ethylglyoxylate) (PEtG). This method consists on using a montmorillonite clay called “Maghnite-H⁺” as an eco-catalyst to replace triethylamine which is toxic. Cationic polymerization experiments are performed in bulk conditions at three temperatures (?40°C, 25°C, 80°C) and in THF solutions at room temperature (25°C). At 25°C, an optimum ratio of 5 wt% of catalyst leads to molar masses up to 22000 g/mol in THF solutions. Polymerizations in bulk conditions lead to slightly lower masses than experiments conducted in THF solutions. However, bulk polymerization of ethyleglyoxylate remains a preferable method in order to avoid the use of a solvent and therefore to stay in the context of green chemistry. The structure of obtained polymers are characterized and confirmed by ¹H and ¹³C NMR. Thermogravimetric Analysis (TGA) shows an enhanced thermal stability for end-capped PEtG compared to non-terminated PEtG. The best conversion rate (92%) is observed in bulk conditions at 25°C for a reaction time of 48h. An activation energy could be calculated from bulk experiments (Ea = 6.9 kJ/mol). An interesting advantage of Maghnite-H⁺ is an easy recoverage by a simple filtration from the polymer solution.     

Copolymerization of ethylene and 1-butene using a Cr—silica catalyst in a slurry reactor

A novel slurry reactor was used to investigate the copolymerization behavior of ethylene and 1-butene in the presence of 1 wt % Cr on Davison silica (Phillips-type) catalyst over the temperature range of 0–50°C, space velocity of about 0.0051 [m³ (STP)]/(g of catalyst) h, and a fixed ethylene to 1-butene feed mole ratio of 95 : 5. The effect of varying the ethylene to 1-butene feed ratios, 100 : 0, 96.5 : 3.5, 95 : 5, 93 : 7, 90 : 10, 80 : 20, and 0 : 100 mol/mol at 50°C was also studied. The addition of 1-butene to ethylene typically increased both copolymerization rates and yields relative to ethylene homopolymerization with the same catalyst, reaching a maximum yield for an ethylene: 1-butene feed ratio of 95 : 5 at 50°C. The incorporation of 1-butene within the copolymer in all cases was less than 5 mol %. The average activation energy for the apparent reaction rate constant, k_a, based on total comonomer mole fraction in the slurry liquid for the ethylene to 1-butene feed mole ratio of 95 : 5 in the temperature range of 50–30°C measured 54.2 kJ/mol. The behavior for temperatures between 30 to 0°C differed with an activation energy of 98.2 kJ/mol; thus, some diffusion limitation likely influences the copolymerization rates at temperatures above 30°C. A kinetics analysis of the experimental data at 50°C for different ethylene to 1-butene feed ratios gave the values of the reactivity ratios, r₁ = 27.3 ± 3.6 and r₂ ≅ 0, for ethylene and 1-butene, respectively. © 1996 John Wiley & Sons, Inc.     

Kristallstruktur,Phasenumwandlung und Kaliumionenleitfähigkeit von Kaliumtrifluormethylsulfonat

Crystal Structure, Phase Transition, and Potassium Ion Conductivity of Potassium Trifluoromethanesulfonate According to the results of temperature dependent powder diffractometry (Guinier‐Simon‐technique) potassium trifluoromethanesulfonate is dimorphic. The phase transition occurs between –63 °C and –45 °C. The low‐temperature modification crystallizes monoclinic with a = 10.300(3) Å, b = 6.052(1) Å, c = 14.710(4) Å, β = 111.83(2)° (–120 °C) and the room‐temperature modification with a = 10.679(5) Å, b = 5.963(2) Å, c = 14.624(5) Å, β = 111.57(3)°, Z = 6, P2₁. According to single crystal structure determination, potassium trifluoromethanesulfonate consists of three different potassium‐oxygen‐coordination polyhedra, linked by sulfur atoms of the trifluoromethanesulfonate groups. This results in a channel structure with all lipophilic trifluoromethane groups pointing into these channels. By means of DSC, the transition temperature and enthalpy have been determined to be –33 °C and 0.93 ± 0.03 kJ/mol, respectively. The enthalpy of melting (237 °C) for potassium trifluoromethanesulfonate is 13.59 kJ/mol, the potassium ionic conductivity is 3.68 · 10^–6 Scm^–1 at 205 °C.     

Improvement of the proton exchange membrane fuel cell performances by optimization of the hot pressing process for membrane electrode assembly

The present study deals with PEM fuel cells, namely with the optimization of the hot pressing process for membrane electrode assembly (MEA) fabrication. Designs of experiments (DoE) have been used for evaluating the effect of hot pressing parameters (pressure, temperature, and time) on the MEA electrical performances. Full factorial 2³ DoE showed that the most important parameter is the pressing temperature. Surface response methodology indicated a non-monotonous behavior of the MEA electrical performances with respect to the pressing temperature. The MEA electrical performances increased with the pressing temperature in the temperature range from 100 to 115 °C, and decreased significantly in the temperature range from 115 to 130 °C. This behavior was attributed to drastic changes of the Nafion® 112 membrane properties and membrane/electrode interface over this temperature range. Observations of the MEA cross-section structure by scanning electron microscopy confirmed such hypotheses. Thermo-mechanical properties of Nafion® as determined by dynamic scanning calorimetry allowed estimating the glass transition temperature at ca. T _g?≈?117 °C in the conditions of the present study. The higher H₂/air fuel cell performance of ca. 0.8 W cm^?2 was obtained with the optimized pressing temperature for MEA fabrication of ca. 115 °C close to the T _g temperature of Nafion® 112, whereas for higher temperature the structure of the Nafion® membrane and of the membrane–electrode interface is damaged.     

Correlation amongst gas barrier behaviour,temperature and thickness in BOPP films for food packaging usage: A lab-scale testing experience

Permeability of gases in polymers depends strongly upon the polymer structure, the gas type, as well as the conditions of temperature and film thickness. The in-use temperature and thickness of the polymer membrane can play the most important role on preservation and prolongation of food shelf-life. In this work the gas transmission parameters of six Bi-axially Oriented Polypropylene (BOPP) films were investigated as a function of temperature, gas type and thickness. O₂, CO₂, N₂, N₂O, C₂H₄, Air (79%N₂/21%O₂) and Modified Atmosphere (MA) of 79%N₂O/21%O₂ were used as test gas. In order to understand the kinetic of the process, by the activation energy determination, samples were tested at a different temperature, from 10 °C to 40 °C. Gas Transmission Rate (GTR), solubility (S) and diffusion (D) relationship was investigated. The gas/thickness/temperature correlation was reflected in the obtained perm-selectivity ratios and a good linear correlation was found only at 23 °C. Deviations recorded were attributed to temperature fluctuations. Gas transmission process follows the Arrhenius model while the solubility/diffusion process shows consistent deviation, correlated to the temperature and the thickness of the film. By Differential Scanning Calorimetry (DSC) a different crystallinity percentage was recorded, whose influence was evidenced only in the sorption/diffusion processes. The melting temperature remained unchanged. FT-IR Spectroscopy was also carried out to confirm the morphology.     

Sensor Performance of Nanostructured TiO<Subscript>2</Subscript>–SnO<Subscript>2</Subscript> Films Prepared by an Aqueous Sol–Gel Process

Nanostructured TiO₂–SnO₂ thin films and powders were prepared by a facile aqueous particulate sol–gel route. The prepared sols showed a narrow particle size distribution with hydrodynamic diameter in the range 17.2–19.3 nm. Moreover, the sols were stable over 5 months, since the constant zeta potential was measured during this period. The effect of Sn:Ti molar ratio was studied on the crystallisation behaviour of the products. X-ray diffraction analysis revealed that the powders were crystallised at the low temperature of 400 °C containing anatase-TiO₂, rutile-TiO₂ and cassiterite-SnO₂ phases, depending on annealing temperature and Sn:Ti molar ratio. Furthermore, it was found that SnO₂ retarded the anatase to rutile transformation up to 800 °C. The activation energy of crystallite growth was calculated in the range 0.96–6.87 kJ/mol. Transmission electron microscope image showed that one of the smallest crystallite sizes was obtained for TiO₂–SnO₂ binary mixed oxide, being 3 nm at 600 °C. Field emission scanning electron microscope analysis revealed that the deposited thin films had nanostructured morphology with the average grain size in the range 20–40 nm at 600 °C. Thin films produced under optimized conditions showed excellent microstructural properties for gas sensing applications. They exhibited a remarkable response towards low concentrations of CO gas at low operating temperature of 200 °C, resulting in increased thermal stability of sensing films as well as a decrease in their power consumption.     

Synthesis and characterization of new soluble thermally stable poly(azomethine‐ether‐imide)s: discerning the possibility for high temperature applications

A new series of polyimides was synthesized by the condensation of monomers (azomethine‐ether diamine, DA‐1 and DA‐2) with pyromelliticdianhydride (PMDA), 3,4,9,10‐perylenetetracarboxylic dianhydride (PD) and 3,3′4,4′‐benzophenonetetracarboxylic dianhydride (BD). The structural explications of monomers and polyimides was conducted by FT‐IR, ¹H NMR and elemental analysis. All polyimides were found soluble in polar aprotic solvents and found to be semicrystalline in nature confirmed by XRD. The inherent viscosities were found in the range of 0.67–0.77 g/dl. %. Average molecular weight (M_W) and number average molecular weight (Mn) of the polyimides were found in the range of 5.72 × 10⁵ g/mol–6.58 × 10⁵ g/mol and 3.79 × 10⁵ g/mol 4.11 × 10⁵ g/mol respectively. The polyimides exhibited excellent thermal properties having a glass transition temperature T_g in the range of 230–290°C and the 10% weight loss temperature was above 450°C. The values of thermodynamic parameters, activation energy, enthalpy and entropy fall in the range of 45.2–53.90 kJ/mol, 43.5–52.30 kJ/mol and 0.217 kJ/mol k to 0.261 kJ/mol k respectively. Copyright © 2015 John Wiley & Sons, Ltd.