Synthesis and properties of poly ether nitrile sulfone copolymers with pendant methyl groups

Poly ether nitrile and poly ether nitrile sulfone copolymers with pendant methyl groups were prepared by the nucleophilic substitution reaction of 2,6′‐dichlorobenzonitrile with methyl hydroquinone and with varying mole proportions of methyl hydroquinone and 4,4′dihydroxydiphenylsulfone using N‐methyl pyrrolidone as solvent in the presence of anhydrous K₂CO₃. The polymers were characterized by different physicochemical techniques. Copolymer composition was determined using FTIR technique. Thermogravimetric data reveals that all the polymers were stable up to 420°C with a char yield above 40% at 900°C in N₂ atmosphere. The glass transition temperature was found to increase and the activation energy and inherent viscosities were found to decrease with increase in concentration of the 4,4′‐dihydroxydiphenylsulfone units in the polymer. Trimerization reactions are found to be favorable with increase in concentration of methyl hydroquinone units in the polymer. Crystallinity of the polymer was also studied using wide angle X‐ray diffraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1303–1309, 2006     

Synthesis and properties of poly(ether nitrile sulfone) copolymers with pendant methyl groups

Poly(ether nitrile) and poly(ether nitrile sulfone) copolymers with pendant methyl groups were prepared by the nucleophilic substitution reaction of 2,6′‐dichlorobenzonitrile with methyl hydroquinone and with varying mole proportions of methyl hydroquinone and 4,4′‐dihydroxydiphenylsulfone using N‐methyl pyrrolidone as a solvent in the presence of anhydrous K₂CO₃. The polymers were characterized by different physicochemical techniques. Copolymer composition was determined using the FTIR technique. Thermogravimetric data revealed that all polymers were stable up to 420°C with a char yield above 40% at 900°C in a nitrogen atmosphere. The glass‐transition temperature increased and the activation energy and inherent viscosities decreased with an increase in the concentration of the 4,4′‐dihydroxydiphenylsulfone units in the polymer. Trimerization reactions were favorable with an increase in the concentration of methyl hydroquinone units in the polymer. The crystallinity of the polymer was also studied using wide‐angle X‐ray diffraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1987–1994, 2005     

Structural Basis for Intumescence—Part II: Synthesis and Characterization of Intumescent Polymers Containing Spirophosphorus Moiety in the Backbone

Taking the spirophosphorus compound 3,9-dichloro-2,4,8,10-tetraoxo-3,9-diphosphaspiro-[5,5]-undecane-3,9-dioxide as one of the reactive monomers, a family of aromatic spirophosphates was synthesized using dihydric phenols, viz., resorcinol, hydroquinone, 4,4′–dihydroxydiphenyl, bisphenol-A and fluorene dicarbinol as the other monomers. The polymers were synthesized employing melt condensation technique under vacuum and characterized using FT-IR, ¹H-, ¹³C- and ³¹P-NMR spectroscopic methods. The number average molecular weight of the polymers was determined using vapour phase osmometry. Thermal properties of the polymers were studied using differential scanning calorimetry and thermogravimetry techniques. These studies indicated that the polymers containing spirophosphato moiety undergo eruptive degradations in the temperature region 310°–380°C leading to the formation of dense carbonaceous foam. The present study confirmed the spirophosphate structure as an essential requirement to show intumescence.     

Microwave promoted synthesis and characterization of isomeric poly(ether ether ketone)s

A series of isomeric poly(ether ether ketone)s were synthesized using microwave‐assisted method by nucleophilic substitution reaction of hydroquinone and 4,4′‐biphenol with 4,4′‐difluorobenzophenone (DFBP) or 2,4′‐DFBP in the presence of anhydrous K₂CO₃. The polymers with inherent viscosities in the range of 0.20–0.71 dlg^?1 were obtained in quantitative yields and had excellent thermal stability as shown by the temperature of 5% weight loss in nitrogen above 410°C. X‐ray diffraction patterns confirmed the semicrystalline character of some of the polymers. The results also indicate that the reaction time was shortened remarkably and the reaction temperature could be controlled easily. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Synthesis and characterization of soluble poly(arylene ether ketone)s with high glass transition temperature based on 3,6‐bi(4‐fluorobenzoyl)‐N‐alkylcarbazole

3,6‐bi(4‐fluorobenzoyl)‐N‐methylcarbazole and 3,6‐bi(4‐fluorobenzoyl)‐N‐ethylcarbazole were synthesized and used to prepare poly(arylene ether ketone)s (PAEKs) with high glass transition temperatures (T_g) and good solubility. High molecular weight amorphous PAEKs were prepared from these two difluoroketones with hydroquinone, phenolphthalein, 9,9‐bis(4‐hydroxyphenyl)fluorene and 4‐(4‐hydroxylphenyl)‐2,3‐phthalazin‐1‐one, respectively. All these polymers presented high thermal stability with glass transition temperatures being in the range 239–303 °C and a 5% thermal weight loss temperature above 460 °C. Compared with the T_g of phenolphthalein‐based PAEK (PEK‐C), fluorene‐based PAEK (BFEK) and phthalazinone‐based PAEK (DPEK) not containing a carbazole unit, these polymers presented a 30–50 °C increase in T_g. Meanwhile, PAEKs prepared from N‐ethylcarbazole difluoroketone showed good solubility in ordinary organic solvents, and all polymers exhibited excellent resistance to hydrochloric acid (36.5 wt%) and sodium hydroxide (50 wt%) solutions. In particular, phthalazinone‐based PAEK bearing N‐ethylcarbazole afforded simultaneously a T_g of 301 °C with good solubility. Tensile tests of films showed that these polymers have desirable mechanical properties. The carbazole‐based difluoroketones play an important role in preparing soluble PAEKs with high T_g by coordinating the relationship between chain rigidity resulting from the carbazole unit and chain distance from the side alkyl. © 2014 Society of Chemical Industry     

Liquid crystalline aromatic polyesters formed with terephthalic acid,phenyl hydroquinone,and napthalene or anthracene diols

The synthesis and characterization of aromatic copolyesters containing terephthalic acid and phenyl hydroquinone as the major constituents and either 1,4-napthalene diol or 1,4-anthracene diol as the minority comonomer is described. Both polymers melted in the vicinity of 300°C, giving birefringent fluids. Optical microscopy showed Schlieren textures consisting predominantly of inversion walls characteristic of the nematic phase. The clearing temperature was in the vicinity of 460°C, but was accompanied by charring. DSC experiments showed a high glass transition temperature of 130–160°C for both polymers. Crystalnematic and nematic-isotropic endotherms were observed on heating; however, degradation took place near the isotropization temperature. Thus, on cooling, the sequence was reversible only if the previous heating was beyond the crystal-nematic but below the isotropization temperature. The polymers were stable in terms of gross weight loss until about 450°C, though there were indications that crosslinking occurred above about 400°C over a short period of time. The polymers formed low-viscosity injection-molding compounds, but to use them effectively, it would require mold-gate designs that reduce the “jetting” tendency for liquid crystal polymer melts, which result in weld lines. © 1995 John Wiley & Sons, Inc.     

New soluble cyano‐containing poly(arylene ether) copolymers bearing pendant xanthene groups

Homopolymers and copolymers of poly(arylene ether nitrile) (PAEN)‐bearing pendant xanthene groups were prepared by the nucleophilic substitution reaction of 2,6‐difluorobenzonitrile with 9,9‐bis(4‐hydroxyphenyl)xanthene (BHPX) and with various molar proportions of BHPX to hydroquinone (100/0 to 40/60) with N‐methyl‐2‐pyrrolidone (NMP) as a solvent in the presence of anhydrous potassium carbonate. These polymers had inherent viscosities between 0.61 and 1.08 dL/g, and their weight‐average molecular weights and number‐average molecular weights were in the ranges 34,200–40,800 and 17,800–20,200, respectively. All of the PAENs were amorphous and were soluble in dipolar aprotic solvents, including NMP, N,N‐dimethylformamide, and N,N‐dimethylacetamide and even in tetrahydrofuran and chloroform at room temperature. The resulting polymers showed glass‐transition temperatures (T_g's) between 220 and 257°C, and the T_g values of the copolymers were found to increase with increasing BHPX unit content in the polymer. Thermogravimetric studies showed that all of the polymers were stable up to 422°C with 10% weight loss temperatures ranging from 467 to 483°C and char yields of 54–64% at 700°C in nitrogen. All of the new PAENs could be cast into transparent, strong, and flexible films with tensile strengths of 106–123 MPa, elongations at break of 13–17%, and tensile moduli of 3.2–3.7 GPa. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of phenol derivatives on molecular dimensions of poly(N‐vinyl‐2‐pyrrolidone) in aqueous solution

The unperturbed dimensions and thermodynamic parameters of poly(N‐vinyl‐2‐pyrrolidone) (PVP) were studied in aqueous solutions in the presence of certain phenolic cosolutes (phenol, catechol, hydroquinone, resorcinol, and phloroglucinol). The intrinsic viscosities at 25°C and the θ temperature, linear and thermodynamic expansions, and root mean square end to end distances were evaluated for the system that was employed. The sequence was obtained due to the effectiveness of the cosolutes in the order of phloroglucinol > resorcinol > hydroquinone > catechol > phenol. The effects of these cosolutes on the main thermodynamic parameters were reported to be due to the number and position of hydroxyl groups present. The thermodynamic interaction parameter was also evaluated and the enthalpic and entropic contributions were verified. The condition required for the θ temperature to correspond to a Flory interaction parameter of 0.5 was well provided, yielding a θ temperature of almost 0.5 for the system under study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 473–477, 2002; DOI 10.1002/app.10047     

Crosslinking behavior of polyarylene ether nitrile terminated with phthalonitrile (PEN‐t‐Ph)/1,3,5‐Tri‐(3,4‐dicyanophenoxy) benzene (TPh) system and its enhanced thermal stability

A novel polyarylene ether nitrile terminated with phthalonitrile (PEN‐t‐Ph) was synthesized by a simple solution polycondensation of biphenyl and hydroquinone with 2,6‐dichlorobenzonitrile, followed by termination with 4‐nitrophthalonitrile. The PEN‐t‐Ph/1,3,5‐Tri‐(3,4‐dicyanophenoxy) benzene (TPh) system was prepared by cure treatment. The phthalonitrile on PEN‐t‐Ph were thermally crosslinked with TPh in the presence of diamino diphenyl sulfone through cure treatment up to 280–340°C, which led to the transformation from thermoplastic polymers to thermosetting polymers. This is because the phthalonitrile on the PEN‐t‐Ph can react with TPh by forming phthalocyanine ring. The glass transition temperatures of the PEN‐t‐Ph/TPh system increased from 152.4°C to 194.7°C, and the initial decomposition temperature (ranging from 475.3°C to 544.0°C) increased by 68°C after thermal curing. Therefore, their thermal properties can be greatly enhanced by crosslinking. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1363‐1368, 2013     

Diacetylene-containing polymers. XI. Synthesis and characterization of poly(hexa-2,4-diynylene-1,6-dioxydibenzoate) and poly(octa-3,5-diynylene-1,8-dicarboxylate) containing p-nitroaniline groups

Summary Two novel polymers containing p-nitroaniline group in the side chain and diacetylene groups in the main chain, were synthesized, and characterized. The polymers gave films of excellent optical quality by spin coating from DMF or chloroform. The one containing benzoate had a T_g of 103°C and its thermal cross-linking through the diacetylene group started at around 160°C. The one containing pentynoate had a T_g of 35°C and its cross-linking started at around 120°C. It was shown that thermosetting resins with functional groups could be obtained by using diacetylene-containing polymers. Although these two polymers have a same polar dye molecule, the second order nonlinear optical property was so different, showing that the main chains are very important for nonlinear optical property. Irradiation of UV light converted the polymer films to completely insoluble thermoset resins. Received: 13 February 2001/Revised version: 25 July 2001/Accepted: 30 July 2001     

Preparation and characterization of poly (ether ether ketone)s containing benzimidazolone units

A series of novel poly(ether ether ketone)s containing benzimidazolone groups (PNBEEKs) with precise structures in high yields were synthesized from various stoichiometric ratio mixtures of benzimidazolone, 4,4′-dihydroxybenzophenone and 4,4′-difluorobnzophenone via a C–N/C–O coupling reaction process using sulfolane as a solvent. The reaction was carried out at 210 °C in the presence of anhydrous potassium carbonate. The structures of the resulted polymers were characterized by means of FT-IR, ¹H NMR spectroscopy, ¹³C NMR spectroscopy, and elemental analysis, and the results were largely consistent with the proposed structure. XRD studies revealed that the incorporation of benzimidazolone groups increased the crystallinity of the resulted polymers. At the same time, as the benzimidazolone unit content in the copolymer increased, the solvent resistance properties and thermal properties of the prepared polymers improved. The polymers showed high glass transition temperatures (T_g?=?126–221 °C) and high thermal stability (T_d5%?=?497–593 °C in nitrogen, 466–588 °C in air). Moreover, the resulted polymers showed good fluorescence properties and the fluorescence emission peak was 435 nm.     

Synthesis and characterization of poly(ethylene oxide)‐based glycopolymers and their biocompatibility with osteoblast cells

Poly(ethylene oxide)‐block‐poly(methacryl‐d ‐glucopyranoside) (PEO‐GP) and poly(methacryl‐d ‐glucopyranoside) (H‐GP) glycopolymers were synthesized by deacetylation of acetylated polymers which were synthesized via atom transfer radical polymerization. The synthesized glycopolymers were characterized using ¹H NMR, ¹³C NMR and Fourier transform infrared (FTIR) spectroscopies, gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The deacetylated polymers exhibited onset decomposition temperatures about 60 °C lower compared to the polymers having acetyl pendants. The glass transition temperature (T_g) of the acetylated homopolymer was 133 °C and that of the PEO‐based block copolymer was 124 °C. The deacetylated polymers H‐GP and PEO‐GP exhibited T_g values of about ?30 °C. Biocompatibility of the H‐GP and PEO‐GP glycopolymers was obtained by studying osteoblast cell adhesion, viability and proliferation in vitro. The cell viability showed an increase with increasing concentration of H‐GP from 0.1 to 1 µmol L^?1 and then decreased with further increase in its concentration (10–1000 µmol L^?1). PEO‐GP did not show a significant variation in cell viability on variation of its concentration from 0.1 to 1000 µmol L^?1. The significant improvement in biocompatibility with osteoblast cells in the presence of PEO‐GP was considered as due to the covalently bonded PEO segment of the methacrylate glycopolymer block. © 2014 Society of Chemical Industry     

Ring-Opening Polymerization of Epoxidized Soybean Oil

Ring-opening polymerization of epoxidized soybean oil (ESO) catalyzed by boron trifluoride diethyl etherate (BF₃·OEt₂) in methylene chloride was conducted in an effort to develop useful biodegradable polymers. The resulting polymerized ESO (PESO) were characterized using infrared (IR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), ¹H NMR, ¹³C NMR, solid state ¹³C NMR and gel permeation chromatography (GPC). The results indicated that PESO materials were highly crosslinked polymers. They had glass transition temperatures ranging from −16 to −48 °C. TGA results showed the PESO polymers were thermally stable at temperatures up to 220 °C. Decomposition of the polymers was found to occur at temperature greater than 340 °C. GPC results indicated the extracted soluble substances from PESO polymers were ESO dimers, trimers and polymers with low molecular weights. The resulting crosslinked polymers can be converted into hydrogels by chemical modification, such as hydrolysis. These soy based hydrogels will find applications in personal care and health care areas.     

Soluble and crosslinkable poly(phthalazinone ether ketone)s with pendent terminal ethynyl groups: synthesis,characterization and click modification

New poly(phthalazinone ether ketone)s (PPEKs) with pendent terminal ethynyl groups were synthesized by the aromatic nucleophilic substitution (S_NAr) polycondensation reaction of a new bisphenol monomer, 2‐(3‐ethynylphenyl)hydroquinone, with 4‐(4′‐hydroxyphenyl)phthalazin‐1(2H)‐one and 4,4′‐bis(4‐fluorophenyl) ketone, followed by click modification reaction with 1‐azidopyrene. Fourier transform infrared and NMR spectral data of the model compound indicated that the terminal ethynyl groups were stable in S_NAr reaction conditions, thus allowing the synthesis of the desired polymers. The PPEKs obtained with glass transition temperature (T_g) in the range 152–245 °C were amorphous, characterized by wide‐angle X‐ray diffraction, and dissolved in organic solvent to cast into transparent and flexible films. Differential scanning calorimetry results indicated that the curing reaction of the terminal ethynyl groups of the copolymers took place upon heating to 250 °C. The T_g of cured PPEKs was increased to about 260 °C. They also exhibited excellent thermal stability with 5% weight loss temperatures ranging from 448 to 527 °C in various atmospheres. The PPEKs with pendent terminal ethynyl groups were subsequently functionalized with pyrene through click reaction. A dilute chloroform solution displayed a red‐shifted emission profile. © 2014 Society of Chemical Industry     

Influence of melt stability on the crystallization of bis(4-aminophenoxy)benzene-oxydiphthalic anhydride based polyimides

Novel high performance semicrystalline polyimides, based on controlled molecular weight phthalic anhydride (PA) endcapped 1,4-bis(4-aminophenoxy)benzene (TPEQ diamine) and oxydiphthalic dianhydride (ODPA), were synthesized. They exhibited excellent thermal stability in nitrogen and air atmospheres as determined by thermogravimetric analysis (TGA). The glass transition temperatures (T_g) for these polymers ranged from 225°C for the 10,000 M_n (10K) polymer, to 238°C for the 30,000 (30K) M_n material. The observed melting temperatures for all the polymers were ∼420°C. The crystallization behavior of these polymers showed a strong molecular weight dependence, as illustrated by the observation that the 10K and 12.5K polymers crystallized with relative ease, whereas the 15K, 20K, and 30K polymers showed little or no ability to undergo thermal recrystallization. The thermal stability of these polymers above T_m was investigated by studying the effect of time and temperature in the melt on the cold crystallization and melting of these polymers. Increased time and temperature in the melt resulted in lower crystallinity because of melt state degradation, such as crosslinking and branching, as evidenced by an increase in melt viscosity, which was more prominent for the higher molecular weight polymers.     

Isothiocyanate derivatives of soybean oil triglycerides: Synthesis,characterization, and polymerization with polyols and polyamines

In this article, a novel two step synthesis of soy oil based isothiocyanate is described. Allylicaly brominated soybean oil (ABSO) was reacted first with ammonium thiocyanate in tetrahydro furan to form allylic thiocyanates. These compounds were then converted to isothiocyanated soybean oil (ITSO) by a thermal rearrangement. Conversion was found to be 70%. The structure of the ITSO was characterized by IR and ¹ H‐NMR techniques. Then ITSO was reacted with ethylene glycol, glycerol, and castor oil to produce polythiourethanes and ethylene diamine and triethylene tetra amine to produce polythioureas. Thermal properties of the products were determined by DSC and TGA techniques. DSC traces showed T_g's for ethylene glycol polythiourethane at ?39 and 58°C, for glycerol polythiourethane at ?39 and 126°C, for castor oil polythiourethane at ?38°C and ?17°C, for ethylene diamine polythiourea at ?45°C, and for triethylene tetra amine poly thiourea at ?39°C. Additionally, DSC analysis of polythioureas showed an endotherm at around 100°C. All of the polymers started to decompose around 200°C. Tensile properties of the polymers were determined. Polythiourethanes showed higher tensile strength and lower elongation when compared with their urea analogs. Stress at break values of the polymers were 1.2 MPa for glycerol polythiourethane, 0.6 MPa for ethylene glycol polythiourethane, 0.5 MPa for ethylene diamine polythiourea, and 0.9 MPa for triethylene tetra amine polythiourea polymers. Unfortunately, polymers synthesized showed poor solvent resistance. All polymers swelled and disintegrated in CH₂Cl₂ in 5 h. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermomechanical behavior of poly(carborane–siloxane)s containing ?CB5H5C? cages

The thermomechanical spectra of two new carborane–siloxane polymers containing five-boron carborane cages in the backbones are reported and discussed. The polymers are the homopolymer, HO? [Si(CH₃)₂? CB₅H₅C? Si(CH₃)₂? O? ]_nH, and the random copolymer with 20 mole-% of the ten-boron meta-carborane analogue, ? [Si(CH₃)₂? CB₁₀H₁₀C? Si(CH₃)₂? O? ]. The mechanical spectra (～1 cps) were determined from ?180° → +625° → ?180°C (ΔT/Δl = 3.6°C/min for T > 25°C and 2°C/min for T < 25°C) using the semimicro thermomechanical technique, torsional braid analysis. In nitrogen, both polymers displayed secondary transitions at ?140°C. The glass transition (T_g) for the homopolymer was ?60°C and for the copolymer was ?52°C. The homopolymer had a melting point of +70°C. The copolymer was amorphous. The high-temperature stability in nitrogen of both polymers appeared to be identical; thermal stiffening commenced at 400°C, continued to 625°C, and resulted in materials that were typical of highly crosslinked resins. In air, the homopolymer began to stiffen catastrophically near 270°C, while the copolymer began to stiffen similarly nearly 50°C higher. The intrinsic elastomeric nature together with the thermomechanical results prompted further study of the copolymer. Thermomechanical cycling studies in nitrogen and air are reported for the copolymer. Some correlating TGA and DTA are also discussed.     

Utilization of N,N-diethyl-3,5-difluorobenzene sulfonamide to prepare functionalized poly(arylene ether)s

A series of poly(arylene ether)s carrying a pendant diethyl sulfonamide group was prepared by the meta activated nucleophilic aromatic substitution reaction of a new aryl difluoride monomer, N,N-diethyl-3,5-difluorobenzene sulfonamide. The synthesis of N,N-diethyl-3,5-difluorobenzene sulfonamide was achieved via the one-step reaction of diethyl amine with commercially available 3,5-difluorobenzenesulfonyl chloride. Model reactions and NMR data indicated that the fluoride atoms were sufficiently activated by the sulfonamide group, located in the meta position, to provide access to high molecular weight poly(arylene ether)s. The corresponding poly(arylene ether)s, were prepared by reaction of N,N-diethyl-3,5-difluorobenzene sulfonamide with bisphenol A, bisphenol AF, 4,4′-biphenol, hydroquinone, resorcinol, and 4,4′-dihydroxydiphenyl ether. The polymers were characterized via NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. The sulfonamide based poly(arylene ether)s displayed moderate thermal stability with 5% weight loss temperatures ranging from 366 to 385 °C, but possessed relatively low glass transition temperatures, 72–142 °C.     

Synthesis and characterization of poly(ether sulfone) copolymers

Poly(ether sulfone) copolymers I–V were synthesized by the nucleophilic substitution reaction of 4,4-dichlorodiphenyl sulfone with varying mole proportions of 4,4-isopropylidene diphenol (bisphenol A) and 4,4-dihydroxydiphenyl sulfone (bisphenol S) using sulfolane as the solvent in the presence of anhydrous K₂CO₃. The polymers were characterized by different physicochemical techniques. The glass transition temperature was found to decrease with increase in the concentration of bisphenol A units in the polymers. All polymers were found to be amorphous. Thermogravimetric studies showed that all the polymers were stable up to 400°C with a char yield of about 36% at 900°C in a nitrogen atmosphere. ¹³C-NMR spectral analysis reveals that bisphenol S-based triads are preferentially formed compared to bisphenol-A triads, indicating greater reactivity of bisphenol S toward dichlorodiphenyl sulfone. The overall activation energy for the thermal decomposition of bisphenol A-based polymer (1) is much higher than that of bisphenol S-based polymer ( II ). This was attributed to the modification of the backbone of polymer I during the initial cleavage of the C—CH3 bond of the isopropyledene group. Polymer II decomposes by cleavage of the C—SO2 bond. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 743–750, 1998     

The effect of catalyst and heat treatment on the properties of carbon–metal composites

Carbon gel and carbon–nickel–palladium doped gels (C–Ni–Pd) were prepared by carbonising resorcinol–formaldehyde (RF) hydrogel and resorcinol–formaldehyde–nickel–palladium (RF–Ni–Pd) hydrogels at 900 °C in a nitrogen atmosphere. RF and RF–Ni–Pd hydrogels were synthesized through sol–gel polycondensation followed by ambient drying. The aim of this study was the determination of the effect of heat treatment in air at 450 °C on the properties of C–Ni–Pd gels prepared using different Pd salts. In the present work, Ni was added as acetate whereas Pd was added as acetate (CA–Ni–Pd) and as chloride (CB–Ni–Pd). Samples were examined by scanning electron microscopy and X-ray diffraction. Surface area was characterized by N₂ adsorption at ?195.5 °C. Thermogravimetric analysis was carried out in order to determine the thermal characteristics of carbon gel and nickel–palladium composites in air atmosphere. CA–Ni–Pd composite had a higher activity and two-phase reaction compared to the CB–Ni–Pd composite. Further improvement of the electrolyte diffusion into the particles of nickel and palladium was obtained by oxidative thermal treatment. During this process a structural modification of the material took place, consequently leading to changes in the electrochemical properties of the composites.