Isoconversional and thermal methods of kinetic analysis of 2,4‐dihydroxybenzophenone copolymer resin

A copolymer (2,4‐DHBPOF) synthesized by the condensation of 2,4‐dihydroxybenzophenone and oxamide with formaldehyde in the presence of acid catalyst with varying the molar proportions of the reacting monomer. Composition of the copolymer has been determined by elemental analysis. The copolymer has been characterized by UV–visible, FTIR, and ¹H NMR spectroscopy. The morphology of synthesized copolymer was studied by scanning electron microscopy (SEM). The activation energy (E_a) and thermal stability calculated by using Sharp‐Wentworth, Freeman–Carroll, and Freidman's method. Thermogravimetric analysis (TGA) data were analyzed to estimate the characteristic thermal parameters. Freeman–Carroll and Sharp Wentworth methods have been used to calculate activation energy and thermal stability. The activation energy (E_a) calculated by using the Sharp‐Wentworth has been found to be in good agreement with that calculated by Freeman–Carroll method. Thermodynamic parameters such as free energy change (ΔF), entropy change (ΔS), apparent entropy change (S*), and frequency factor (Z) have also been evaluated based on the data of Freeman–Carroll method. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Resin II: Thermal degradation studies of terpolymer resins derived from 2,2′‐dihydroxybiphenyl,urea, and formaldehyde

The terpolymer resins have been synthesized by the condensation of 2,2′‐dihydroxybiphenyl with urea and formaldehyde in the presence of 2M HCl as a catalyst and with varying molar proportions of reactants. Elemental analysis, IR, NMR and UV–Visible spectral study, and TGA–DTA analysis characterized the resins. The number average molecular weight was determined by nonaqueous conductometric titrations. Thermal studies of the resins have been carried out to determine their mode of decomposition, activation energy, order of reaction, frequency factor, entropy change, free energy, and apparent entropy change. Freeman–Carroll and Sharp–Wentworth methods have been applied for the calculation of kinetic parameters, while the data from Freeman–Carroll method have been used to determine various thermodynamic parameters. The order of thermal stabilities of terpolymers has been determined using TGA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 227–232, 2006     

Synthesis,characterization, and thermal degradation studies of copolymer resin derived from p-cresol,melamine, and formaldehyde

Copolymers (p-CMF) synthesized by the condensation of p-cresol and melamine with formaldehyde in the presence of an acid catalyst and using varied molar proportion of the reacting monomers. Copolymer resin compositions were determined on the basis of their elemental analysis. The number average molecular weight of these copolymers was determined by conductometric titration in nonaqueous media. Solution viscosity measurements in dimethyl sulfoxide (DMSO) were carried out to ascertain the characteristic functions and constants of the copolymer resins. The copolymer resins were further characterized byUV–visible absorption spectra in the nonaqueous medium, Infra-red (IR) spectra, and the nuclear magnetic resonance (NMR) spectra. Thermal studies of the resins were carried out to determine their mode of decomposition, the activation energy (E_a), order of reaction (n), frequency factor (Z), entropy change (ΔS), free energy change (ΔF), and apparent entropy change (S*). Thermal decomposition curves were discussed with careful attention of minute details. The Freeman-Carroll and Sharp-Wentworth methods have been used to calculate thermal activation energy and thermal stability. Thermal activation energy (E_a) calculated with these methods are in agreement with each other. The data from the Freeman-Carroll methods have been used to determine various thermodynamic parameters. The order of thermal stability of copolymers has been determined using TGA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis, Spectral, Morphology, Thermal Degradation Kinetics and Antibacterial Studies of Terpolymer Metal Complexes

Terpolymer metal complexes involving transition metal ions such as Cu(II), Mn(II) and Zn(II) were prepared using a terpolymer ligand derived from anthranilic acid–phenyl hydrazine–formaldehyde (APHF). The terpolymer ligand and its metal complexes were intended to spectral characterizations viz. FTIR, electronic, ESR, ¹H NMR and ¹³C NMR to elucidate the structural confirmations. The number, weight, and size average molecular weights of the terpolymer ligand were determined by gel permeation chromatography (GPC). The empirical formula of the repeating unit for both the terpolymer ligand and its metal complexes was clearly justified by elemental analysis. The thermal stability of the ligand and its metal complexes was established by thermogravimetric analysis (TGA). On basis of the TGA data, the kinetic and thermodynamic parameters such as activation energy (E _a), order of reaction (n), entropy change (ΔS), apparent entropy (S*), frequency factor (Z) and free energy change (ΔF) were calculated using Freeman–Carroll and Sharp–Wentworth methods. Further the degradation mechanism for the thermal decomposition was also identified from Phadnis–Desphande method. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were used to establish the surface morphology and nature of the terpolymer ligand and its metal complexes. In addition, the terpolymer ligand and its metal complexes were screened against the growth of few bacteria and their inhibitions were measured and reported.     

Transition Metal Complexes of a Novel Polymeric Ligand: Thermal Degradation Kinetics and In Vitro Antibacterial Applications

A novel polymeric ligand poly(2-amino-3-((2-methyl-4-nitrophenylamino)methyl)benzoic acid) was synthesized using solution condensation technique in acid medium. Metal complexes were prepared using the polymer as ligand. The synthesized ligand and its metal complexes were characterized by FTIR, electronic, ESR and NMR (¹H and ¹³C) spectroscopy. The number, weight, size average molecular weights of the ligand were calculated by gel permeation chromatography. The surface morphology and the nature of the synthesized compounds were examined by SEM and XRD. The thermal behavior of the compounds was determined by thermogravimetric analysis. Thermal degradation kinetics such as activation energy (E_a), order of reaction (n) and thermodynamics viz. entropy change (ΔS), apparent entropy (S*), frequency factor (Z) and free energy change (ΔF) were also evaluated for the ligand and its metal complexes by Freeman–Carroll, Sharp–Wentworth methods. Thermal degradation mechanistic model was also proposed by Phadnis–Deshpande method. In vitro antibacterial assay was analyzed for the synthesized compounds against various pathogenic bacterial strains such as Shigella sonnei, Escherichia coli, Klebseilla species, Staphylococcus aureus, Bacillus subtilis and Salmonella typhimurium species. From the assay, the ligand and its metal complexes possess commendable antibacterial activity and hence the synthesized compounds can act as potential antibacterial agents.     

Kinetics of thermal decomposition and antimicrobial screening of terpolymer resins

Polycondensation technique was employed to synthesize terpolymer resins of anthranilic acid, urea, and formaldehyde (AUF-I, II, and III) in dimethyl formamide medium with varying mole proportions. The terpolymer was characterized by infra-red, nuclear magnetic resonance (¹H and ¹³C) spectroscopy, gel permeation chromatography (GPC), and scanning electron microscopy (SEM). The thermal decomposition pattern and the kinetics of thermal decomposition of the terpolymers were investigated by thermogravimetric analysis (TGA) in a static nitrogen atmosphere at a heating rate of 20 °C/min. Freeman–Carroll and Sharp–Wentworth methods have been adopted to evaluate the kinetic and thermodynamic parameters such as thermal activation energies (E _a), order of the reaction (n), entropy change (ΔS), free energy change (ΔF), apparent entropy (S*), and frequency factor (Z). The thermal decomposition model for the terpolymers was also proposed using Phadnis–Deshpande method. The synthesized terpolymer resins were screened for antimicrobial activity against pathogenic bacteria and fungi. The resins show potent inhibition against bacteria such as Escherichia coli, Klebsiella, Staphylococcus aureus, and Pseudomonas aeruginosa and fungi viz. Aspergillus flavus, Aspergillus niger, Penicillium species, Candida albicans, Cryptococcus neoformans, and Mucor species.     

Metal Complexes of a Novel Terpolymer Ligand: Synthesis, Spectral, Morphology, Thermal Degradation Kinetics and Antimicrobial Screening

2-amino-6-nitro-benzothiazole and thiosemicarbazide with formaldehyde (BTF) terpolymer ligand and its metal complexes have been synthesized. The plausible structure of the synthesized BTF terpolymer ligand was elucidated on the basis of elemental analysis and spectral studies such as FTIR, UV-Vis, ¹H and ¹³C NMR spectroscopy. Gel permeation chromatography (GPC) was used to determine the molecular weight of the terpolymer. The terpolymer metal complexes were analyzed by elemental analysis, molar conductivity measurements, and magnetic susceptibilities. The structure and geometry of the metal complexes were confirmed by various spectral techniques viz. electronic, ESR, FTIR and NMR spectroscopy. The morphology of the BTF terpolymer ligand and its metal complexes was examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The thermal decomposition behaviour of the terpolymer ligand and its complexes was determined using thermogravimetric analysis (TGA). Freeman–Carroll (FC), Sharp–Wentworth (SW) and Phadnis–Deshpande (PD) methods were used to calculate the thermal activation energy (E_a), order of reaction (n), entropy change (ΔS), free energy change (ΔF), apparent entropy (S*) and frequency factor (Z) from the TGA data. Phadnis–Deshpande method was also used to propose the thermal degradation model for the decomposition pattern of the terpolymer ligand. The terpolymer ligand and its metal complexes were screened for its antimicrobial activity against chosen microbes.     

Coordination Polymeric Chain Assemblies of Some Metal Ions with BHQPP

A few coordination chain polymeric assemblies of the type [M(H₂L)(H₂O)₂]_n·xH₂O [where M = Mn(II), Cu(II) and Zn(II) x = 1; Co(II) and Ni(II) x = 2, H₂L = 2,2′-bis-4-[(8-hydroxy-5-quinoline methylenoxy) phenyl] propane] (BHQPP) have been investigated. Structural and spectroscopic properties have been determined by elemental analyses, infrared spectra, electronic spectra, magnetic measurements and thermo-gravimetric analyses. Magnetic moment and reflectance spectral studies reveal that an octahedral geometry is present in all the prepared coordination polymers. The kinetic parameters such as order of reaction (n) and the energy of activation (Ea) were determined using the Freeman–Carroll method. The pre-exponential factor (A), the activation entropy (ΔS^#), the activation enthalpy (ΔH^#) and the free energy of activation (ΔG^#) have been calculated.     

Study of thermal behavior of polyimides containing pendent-substituted azobenzene units

Thermal stability and degradation kinetic of the polyimides containing pendent-substituted azobenzene units were investigated by thermogravimetric analysis in nitrogen at different heating rates. Freeman–Carroll, Coats–Redfern and Flynn–Wall–Ozawa methods were utilized to obtain the kinetic parameters (activation energy E _a, pre-exponential factor A and order of reaction n) or variation of activation energy with conversion degree from thermogravimetric and derivative thermogravimetric curves. The thermogravimetric analysis revealed that the decomposition of azopolyimides proceeds in three or four stages, regardless of heating rate.     

Synthesis,characterization, and kinetic of thermal degradation of oligo‐2‐[(4‐bromophenylimino)methyl]phenol and oligomer‐metal complexes

Oligo‐2‐[(4‐bromophenylimino)methyl]phenol (OBPIMP) was synthesized from the oxidative polycondensation reaction of 2‐[(4‐bromophenylimino)methyl]phenol (BPIMP) with air and NaOCl oxidants in an aqueous alkaline medium between 50 and 90°C. The yield of OBPIMP was found to be 67 and 88% for air and NaOCl oxidants, respectively. Their structures were confirmed by elemental and spectral such as IR, ultraviolet–visible spectrophotometer (UV–vis), ¹H‐NMR, and ¹³C‐NMR analyses. The characterization was made by TG‐DTA, size exclusion chromatography, and solubility tests. The resulting complexes were characterized by electronic and IR spectral measurements, elemental analysis, AAS, and thermal studies. According to TG analyses, the weight losses of OBPIMP, and oligomer‐metal complexes with Co⁺², Ni⁺², and Cu⁺² ions were found to be 93.04%, 59.80%, 74.23%, and 59.30%, respectively, at 1000°C. Kinetic and thermodynamic parameters of these compounds investigated by Coats‐Redfern, MacCallum‐Tanner, and van Krevelen methods. The values of the apparent activation energies of thermal decomposition (E_a), the reaction order (n), preexponential factor (A), the entropy change (ΔS*), enthalpy change (ΔH*), and free energy change (ΔG*) obtained by earlier‐mentioned methods were all good in agreement with each other. It was found that the thermal stabilities of the complexes follow the order Cu(II) > Co(II) > Ni(II). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Studies of new oligomer–metal complexes and their antibacterial activities

A new oligomeric ligand was synthesized from anthranilic acid and 2‐aminopyridine with formaldehyde using a condensation technique in the presence of acid medium. Oligomer–metal complexes were prepared involving transition metal ions Cu(II), Mn(II) and Zn(II) using the synthesized oligomer as ligand. The oligomeric ligand and its metal complexes were characterized using various spectral techniques such as Fourier transform infrared, electronic, electron spin resonance, ¹H NMR and ¹³C NMR. Gel permeation chromatography was used to determine number‐, weight‐ and size‐average molecular weights of the oligomeric ligand. The surface characteristics and nature of the oligomeric ligand and its metal complexes were examined using scanning electron microscopy and X‐ray diffraction analysis. The thermal properties and degradation behaviour of the oligomeric ligand and its complexes were investigated using thermogravimetric analysis. Kinetic and thermodynamic studies of the ligand and its metal complexes were carried out using Freeman–Carroll (FC) and Sharp–Wentworth (SW) methods. From the thermogravimetric data, kinetic and thermodynamic parameters such as activation energy, order of reaction, entropy change, apparent entropy, frequency factor and free energy change were calculated. The activation energy was further calculated from the Phadnis‐Deshpande (PD) method and the degradation mechanism for the thermal decomposition reaction is proposed. The activation energy calculated from the FC and SW methods was in good agreement with that calculated from the PD method. The oligomeric ligand and its metal complexes were screened for antibacterial activity. It was found that the synthesized compounds were potent antibacterial agents. © 2012 Society of Chemical Industry     

Kinetic and thermodynamic studies of an epoxy system diglycidyl ether of bisphenol A/1, 2 diamine cyclohexane/calcium carbonate filler

The curing reaction of an epoxy system consisting of a diglycidyl ether of bisphenol A (BADGE n = 0) and 1,2‐diaminecyclohexane (DCH) with a calcium carbonate filler was studied by differential scanning calorimetry (DSC) and using a scanning electronic microscope (SEM). As a first stage, the optimum content of the filler determined was 20%. From a kinetic study, in which two models were used, parameters such as reaction orders, rate constants, and activation energies were determined. A thermodynamic study allowed calculation of enthalpy (ΔH^#), entropy (ΔS^#), and free‐energy ((ΔG^#) changes. The results were compared to those obtained for the same epoxy systems without the filler. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 291–305, 2000     

Solubilization of Ni Imidazole Complex in Micellar Media of Anionic Surfactants,Sodium Dodecyl Sulfate and Sodium Stearate

The solubilization and physicochemical behavior of a coordination complex of nickel, namely [Ni(im)₆]F₂·5H₂O [hexakis(imidazole)nickel(II) fluoride pentahydrate], in aqueous micellar media of anionic surfactants, i.e., sodium dodecyl sulfate (SDS) and sodium stearate (SS), were investigated by using UV–Vis spectroscopy and electrical conductivity measurements. Spectroscopic techniques were used for the computation of binding constant (K_b), partition coefficient (K_x), change in free energy of binding (ΔG_b), and change in free energy of partition (ΔG_p), whereas electrical conductivity data was helpful to calculate thermodynamic parameters of micellization of surfactants in the presence of the Ni complex, i.e., standard entropy of micellization (ΔS_m), free energy (ΔG_m), and enthalpy of micellization (ΔH_m). It is evident from the results that solubilization of the Ni complex takes place because of electrostatic as well as hydrophobic interactions. The presence of the Ni complex in micellar media increases the critical micelle concentration of both surfactants owing to the structure‐breaking effect.     

A thermodynamic study of the binding of human serum albumin onto N,N′‐diethylaminoethyl dextran microbeads

Adsorption of proteins on solid surfaces is widely studied because of its importance in various biotechnological, medical, and technical applications, e.g., biosensors, cardiovascular implants, and chromatography. Adsorption thermodynamics has been studied on the microbeads of N,N′‐diethylaminoethyl (DEAE) Dextran anion exchanger for the human serum albumin (HSA) at 25, 30, 35, 40, and 45°C. As a result, some thermodynamic parameters like Freundlich constants, thermodynamic equilibrium constant (K_D), standard free energy changes (ΔG_assoc), standard entropy changes (ΔS_assoc), and standard enthalpy change (ΔH_assoc) have been evaluated. Using the linear Van't Hoff plot, ΔH_assoc value of the system for the interaction of bovine serum albumin (BSA)‐adsorbed crosslinked DEAE dextran microbeads was determined as 20.650 kJ/mol. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3942–3947, 2006     

Synthesis and properties of TLCPs with 2,6‐naphthalene‐based mesogen,polymethylene spacer,and nonlinear 4,4′‐thiodiphenyl links

A series of new thermotropic main‐chain liquid crystalline copolyesters were prepared by polycondensation of 2,6‐naphthalenedicarbonyl chloride, 4,4′‐thiodiphenol, and α,ω‐alkanediols (n = 4–10) in diphenyl ether at 200°C. Thermal transition behaviors of these copolyesters were investigated by differential scanning calorimetry. Moreover, their thermal stabilities and mesomorphic textures were studied by thermogravimetric analysis and polarizing optical microscopy, respectively. Corresponding model compounds with terminal mesogenic units and central polymethylene spacers were also synthesized for comparison. Both copolymers and model compounds exhibit odd–even dependency of melting temperatures, transition enthalpy (ΔH_m), and entropy (ΔS_m) on the number of methylene units in the spacer. However, the odd–even effects in model compounds are much more distinctive. Nematic mesophases are the only texture observed in melts, except the model compounds with longer methylene units (n = 8, 10), in which smectic mesophases can be observed. The T_m values of the copolyesters (TDP/HD = 1/1) are between 233 and 259°C, depending on spacer length. The initial decomposition temperatures of the copolyesters are above 419°C under N₂ atmosphere. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1536–1546, 2002     

Synthesis,characterization, conductivity,band gap,and kinetic of thermal degradation of poly‐4‐[(2‐mercaptophenyl) imino methyl] phenol

The oxidative polycondensation reaction conditions of 4‐[(2‐mercaptophenyl) imino methyl] phenol (2‐MPIMP) were studied in an aqueous acidic medium between 40 and 90°C by using oxidants such as air, H₂O₂, and NaOCl. The structures of the synthesized monomer and polymer were confirmed by FTIR, ¹H NMR, ¹³C NMR, and elemental analysis. The characterization was made by TGA‐DTA, size exclusion chromatography (SEC) and solubility tests. At the optimum reaction conditions, the yield of poly‐4‐[(2‐mercaptophenyl) imino methyl]phenol (P‐2‐MPIMP) was found to be 92% for NaOCl oxidant, 84% for H₂O₂ oxidant 54% for air oxidant. According to the SEC analysis, the number‐average molecular weight (M_n), weight‐average molecular weight (M_w), and polydispersity index values of P‐2‐MPIMP were found to be 1700 g mol^?1, 1900 g mol^?1, and 1.118, using H₂O₂; 3100 g mol^?1, 3400 g mol^?1, and 1.097, using air; and 6750 g mol^?1, 6900 g mol^?1, and 1.022, using NaOCl, respectively. According to TG analysis, the weight losses of 2‐MPIMP and P‐2‐MPIMP were found to be 95.93% and 76.41% at 1000°C, respectively. P‐2‐MPIMP showed higher stability against thermal decomposition. Also, electrical conductivity of the P‐2‐MPIMP was measured, showing that the polymer is a typical semiconductor. The highest occupied molecular orbital, the lowest unoccupied molecular orbital, and the electrochemical energy gaps (E′_g) of 2‐MPIMP and P‐2‐MPIMP were found to be ?6.13, ?6.09; ?2.65, ?2.67; and 3.48, 3.42 eV, respectively. Kinetic and thermodynamic parameters of these compounds investigated by MacCallum‐Tanner and van Krevelen methods. The values of the apparent activation energies of thermal decomposition (E_a), the reaction order (n), pre‐exponential factor (A), the entropy change (ΔS*), enthalpy change (ΔH*), and free energy change (ΔG*) were calculated from the TGA curves of compounds. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Activation energy,free energy,enthalpy, and entropy changes associated with viscometric changes of extremely to moderately dilute aqueous solutions of polyvinylpyrrolidone at 288.15–313.15 K

Viscometric behavior of polyvinylpyrrolidone (PVP) was investigated for extremely dilute (0.002–0.010 g dL^?1), dilute (0.02–0.10 g dL^?1), and moderately dilute (0.20–1.00 g dL^?1) solutions at 288.15, 290.15, 293.15, 295.15, 298.15, 300.15, 303.15, 305.15, 308.15, 311.15, and 313.15 K. The experimental data were plotted according to Jones–Dole, Fuoss, and Fedors equations. Intrinsic viscosity ([η]) variation with temperature indicated the existence of different hydrodynamic states of PVP in solution at different temperatures. The PVP was found to show polyelectrolyte behavior in extremely dilute solutions, probably attributable to the presence of partially polarizable >C?O groups in the chain. Activation energy (ΔE), differential enthalpy (?ΔH), entropy (?ΔS), and free energy (?ΔG) changes of viscous flow were derived from flow velocity and taken into account for interpretation of the results to better understand the hydrodynamic and conformational behavior of PVP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 47–55, 2004     

Kinetics of thermal inactivation of transglutaminase from a newly isolated Bacillus circulans BL32

BACKGROUND: This paper describes the modeling of the kinetics of thermal inactivation of transglutaminase (TGase) from a newly isolated Bacillus circulans BL32, isolated from the Amazon environment. The purified enzyme was incubated at temperatures ranging from 30 to 70 °C and values of the thermodynamic inactivation parameters, such as activation energy (ΔE), activation enthalpy (ΔH), activation entropy (ΔS), and free energy (ΔG) for thermal inactivation, were calculated. RESULTS: The kinetics of TGase thermo‐inactivation followed a Lumry–Eyring model. The enzyme was very stable up to 50 °C, with approximately 50% of activity remaining after heating for 12 h. It was completely inactivated by incubation at 70 °C for 2 min. ΔE for TGase was 350.5 kJ mol^?1. ΔH and ΔS for thermo‐inactivation of the TGase were 347.8 kJ mol^?1 and 744 J mol^?1 K^?1 at 50 °C, respectively. Dynamic light scattering measurements suggest that the thermal inactivation of this microbial TGase can be partially attributed to the formation of aggregates. CONCLUSION: These results provide useful information about the thermal characteristics of the microbial TGase from B. circulans BL32 and indicate that this enzyme could be a good candidate for industrial applications. Copyright © 2009 Society of Chemical Industry     

The influence of light on the thermal decomposition of polypropylene fibers

The influence of exposure to artificial light (ultraviolet and visible spectrum) on the thermal degradation process of polypropylene fiber has been investigated. The activation energy E as a kinetic parameter of the fiber thermal decomposition has been defined by means of the Flynn–Wall and Freeman–Carroll methods. The fiber melting temperature range was also defined. The investigations have been made on the basis the of thermal gravimetric analysis and differential thermal gravimetric analysis curves determined at various heating speeds, in the temperature range from 100°–600°C. It was found that thermal stability of polypropylene fiber is reduced by light treatment (i.e., fiber softens and melts at a lower temperature). Activation energy values determined for thermal decomposition of the fiber samples exposed to the influence of light are considerably higher than the values determined on unexposed samples. The decomposition process of aged fiber is more complex and occurs in a larger temperature range. Both the methods used show almost similar results. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2237–2244, 1999     

Thermal decomposition kinetics of thermotropic copolyesters made from trans‐p‐hydroxycinnamic acid and p‐hydroxybenzoic acid

A series of thermotropic copolyesters were synthesized by direct thermal melt polycondensation of p‐acetoxybenzoic acid (PHB) with trans‐p‐acetoxycinnamic acid (PHC). The dynamic thermogravimetric kinetics of the copolyesters in nitrogen were analyzed by four single heating‐rate techniques and three multiple heating‐rate techniques. The effects of the heating rate, copolyester composition, degradation stage, and the calculating techniques on the thermostability and degradation kinetic parameters of the copolyesters are systematically discussed. The four single heating‐rate techniques used in this work include Friedman, Freeman–Carroll, Chang, and the second Kissinger techniques, whereas the three multiple heating‐rate techniques are the first Kissinger, Kim–Park, and Flynn–Wall techniques. The decomposition temperature of the copolyesters increases monotonically with increasing PHB content from 40 to 60 mol %, whereas their activation energy exhibits a maximal value at the PHB content of 50 mol %. The decomposition temperature, activation energy, the order, and the frequency factor of the degradation reaction for the thermotropic copolyester with PHB/PHC feed ratio of 50/50 mol % were determined to be 374°C, 408 kJ/mol, 7.2, and 1.25 × 10²⁹ min^?1, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 445–454, 2004