Synthesis and properties of polyamides and copolyamides based on 2,6-naphthalene dicarboxylic acid

A number of polyamides based on 2,6-naphthalene dicarboxylic acid (NDA) and various aromatic diamines were synthesized in N-methyl pyrrolidone (NMP) containing lithium chloride (LiCl) or calcium chloride (CaCl₂) by direct polycondensation using triphenyl phosphite and pyridine. The best reaction conditions for polycondensation were determined in terms of factors such as the amount of the solvency-promoting reagent such as LiCl or CaCl₂ and the initial reactant concentration. Thus, almost all polyamides were obtained with inherent viscosities above 1.0 and up to 3.28 dL/g. Similarly, high molecular weight copolyamides with inherent viscosities of 1.76–3.61 dL/g were prepared from 4,4′-oxydianiline (ODA) and mixed dicarboxylic acids of NDA/terephthalic acid (TPA) or NDA/isophthalic acid (IPA). The solubility of NDA homopolyamides depended on the diamine components. The polyamides derived from meta-, sulfone-, or alkylene-linked diamine showed increased solubility. Copolymerization of ODA with NDA/IPA led to a significant increase in solubility, whereas with NDA/TPA, it gave a limited improvement. All the homopolyamides and copolyamides showed an amorphous X-ray diffraction pattern. Almost all the polymers soluble in aprotic solvents can be solution-cast into strong and tough films. Glass transition shifts of some NDA polyamides can be observed in the differential scanning calorimetry (DSC) curves ranging from 243 to 345°C. Most NDA/IPA–ODA copolyamides also showed clear transitions in the range of 255–268°C. In nitrogen, all the polymers showed no significant weight loss up to 400°C, and their 10% weight loss temperatures were recorded in the range of 434–541°C. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of new aromatic poly(amide–imide)s based on 4‐aryl‐2,6‐bis(4‐trimellitimidophenyl) pyridines

New diimide–dicarboxylic acids, ie 4‐phenyl‐2,6‐bis(4‐trimellitimidophenyl)pyridine and 4‐p‐biphenyl‐2,6‐bis‐(4‐trimellitimidophenyl)pyridine, were synthesized by the condensation reaction of 4‐phenyl‐2,6‐bis(4‐aminophenyl)pyridine and 4‐p‐biphenyl‐2,6‐bis(4‐aminophenyl)pyridine with trimellitic anhydride in glacial acetic acid or dimethylformamide. The monomers were fully characterized by FT‐IR and NMR spectroscopies, and elemental analyses. A series of novel poly(amide–imide)s with inherent viscosities of 0.68–0.87 dl g^?1 was prepared from the two diimide–diacids with various aromatic diamines by direct polycondensation. The poly(amide–imide)s were characterized by FT‐IR and NMR spectroscopies. The λ_max data for the resulting poly(amide–imide)s were in the range of 260–292 nm. These polymers exhibited good solubilities in polar aprotic solvents. The 10 % weight loss temperatures are above 485 °C under a nitrogen atmosphere. Copyright © 2004 Society of Chemical Industry     

Preparation and properties of new polycyclic aliphatic polyamides base on diamantane

A series of novel polycyclic aliphatic polyamides was synthesized by direct polycondensation of the 1,6-diamantane dicarboxylic acid with various alicyclic diamines in N-methyl–2–pyrrolidone (NMP) containing lithium chloride, using triphenyl phosphite and pyridine as a condensing agent. The polyamides had inherent viscosities of 0.33–0.49 dL/g. The glass transition temperatures of the these polyamides were in the range of 200–220°C, and the 5% weight loss temperatures were in the range were 290–319°C in nitrogen. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of polyamides and poly(amide‐imide)s derived from 2,6‐bis(3‐aminophenoxy)benzonitrile or 2,6‐bis(4‐aminophenoxy)benzonitrile

A series of polyamides and poly(amide‐imide)s was prepared by direct polycondensation of ether and nitrile group containing aromatic diamines with aromatic dicarboxylic acids and bis(carboxyphthalimide)s respectively in N‐methyl 2‐pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. New diamines, such as 2,6‐bis(4‐aminophenoxy)benzonitrile and 2,6‐bis(3‐aminophenoxy)benzonitrile, were prepared from 2,6‐dichlorobenzonitrile with 4‐aminophenol and 3‐aminophenol, respectively, in NMP using potassium carbonate. Bis(carboxyphthalimide)s were prepared from the reaction of trimellitic anhydride with various aromatic diamines in N,N′‐dimethyl formamide. The inherent viscosities of the resulting polymers were in the range of 0.27 to 0.93 dl g^?1 in NMP and the glass transition temperatures were between 175 and 298 °C. All polymers were soluble in dipolar aprotic solvents such as dimethylsulfoxide, dimethylacetamide and NMP. All polymers were stable up to 350 °C with a char yield of above 40 % at 900 °C in nitrogen atmosphere. All polymers were found to be amorphous except the polyamide derived from isophthalic acid and the poly(amide‐imide)s derived from diaminodiphenylether and diaminobenzophenone based bis(carboxyphthalimide)s. Copyright © 2004 Society of Chemical Industry     

Synthesis and properties of organosoluble polynaphthalimides bearing ether linkages and phthalide cardo groups

A series of organic‐soluble polynaphthalimides (PNI) bearing flexible ether links and phthalide cardo group were synthesized from 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA) with 3,3‐bis[4‐(4‐aminophenoxy)‐3‐methylphenyl]phthalide (BAMP) and its equimolar mixtures with other dietheramines by high‐temperature solution polycondensation in m‐cresol. The PNIs had moderate to high inherent viscosities in the range of 1.24–2.25 dL/g and could afford flexible and tough films with tensile strengths of 97–138 MPa by casting their m‐cresol solutions. These PNIs exhibited high thermal stability, with glass transition temperature of 291°C–321°C, 10% weight‐loss temperatures above 542°C, and char yields at 800°C in nitrogen higher than 56%. In comparison with PNIs without the BAMP component, these BAMP‐modified PNIs revealed an enhanced solubility and film‐forming capability. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1104–1109, 2007     

Modified poly(ether–imide–amide)s with pendent benzazole structures: Synthesis and characterization

Three series of novel modified poly(ether–imide–amide)s (PEIAs) having pendent benzazole units were prepared from diimide–dicarboxylic acids, including 2-[3,5-bis(4-trimellitimidophenoxy) phenyl]benzimidazole, 2-[3,5-bis(4-trimellitimidophenoxy) phenyl]benzoxazole, and 2-[3,5-bis(4-trimellitimidophenoxy) phenyl]benzothiazole, with various diamines by direct polycondensation in N-methyl-2-pyrrolidone with triphenyl phosphite and pyridine as condensing agents. These new diimide–dicarboxylic acids containing ether linkages and benzazole pendent groups were synthesized by the condensation reaction of 5-(2-benzimidazole)-1,3-bis(4-aminophenoxy)benzene, 5-(2-benzoxazole)-1,3-bis(4-aminophenoxy)benzene, or 5-(2-benzothiazole)-1,3-bis(4-aminophenoxy)benzene with trimellitic anhydride, respectively. All of the polymers were obtained in quantitative yields with inherent viscosities of 0.39–0.65 dL/g. For comparative purposes, the corresponding unsubstituted PEIAs were also prepared by the reaction of a diimide–dicarboxylic acid monomer lacking benzazole pendent groups, namely, 3,5-bis(4-trimellitimidophenoxy) phenyl, with the same diamines under similar conditions. The solubilities of the modified PEIAs in common organic solvents and their thermal stability were enhanced compared to those of the corresponding unmodified PEIAs. The glass-transition temperature, 10% weight loss temperature, and char yields at 800°C were 19–31°C, 22–57°C and 4–8% higher, respectively, than those of the unmodified polymers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of new polyamides and polyimides containing dioxypyrimidine moiety in the main chain with bulky imidazole pendent group: solubility, thermal and photophysical properties

A new symmetrical diamine monomer containing dioxypyrimidine and two diaryl imidazole bulky pendent group was synthesized by the nucleophilic substitution reaction of 4,6 dihydroxy pyrimidine with the synthesized 2-(2-chloro-5-nitrophenyl)-4,5-diphenyl-1H-imidazole (I). A series of novel fluorescent imidazole-containing polyamides (PAs) with inherent viscosities of 0.52–0.78 dL/g was prepared by direct polycondensation of the diamine with various dicarboxylic acids. These PAs were readily soluble in many organic solvents and could be solution-cast into tough and flexible films. The PAs exhibited glass transition temperatures (T_g)s between 202 and 260 °C, and 10% weight loss temperatures in the range of 345–470 °C in air. In addition, three novel polyimides (PIs) with inherent viscosities of 0.38–0.56 dL/g were prepared by addition reaction of the diamine with commercially available tetracarboxylic dianhydrides and subsequent chemical imidization. The PIs exhibited good solubility in polar solvents such as NMP. These polymers exhibited T_gs in the range of 237–285 °C and their 10% weight-loss temperatures varied from 440 to 520 °C.     

Synthesis and properties of new polyamides based on a hydroxyethyl cinnamide extended from 3,5‐diaminobenzoic acid

A series of new aromatic polyamides containing cinnamide pendent units were prepared from 2′‐(cinnamide)ethyl‐3,5‐diaminobenzoate and various aromatic dicarboxylic acids by the direct polycondensation reaction, with triphenyl phosphite and pyridine as condensing agents. The polyamides were characterized by ¹H NMR, IR, and UV spectroscopy, and gel permeation chromatography. Their thermal stability was studied by thermogravimetric analysis in air, and differential scanning calorimetry. These polymers were readily soluble in polar aprotic solvents and can be cast from their solutions in flexible and tough films. Glass transition temperatures (T_gs) of these polyamides were observed in the range of 225–245°C. Their inherent viscosities varied from 0.77 to 1.12 dL/g that corresponded to weight–average and number–average molecular weights of 39,000–72,700 and 18,800–29,000, respectively. These polymers can be photochemically crosslinked. The photochemical aspects were revealed by means of UV–vis and IR analyses onto thin films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2013–2020, 2007     

Synthesis and characterization of new thermally stable aromatic copoly(ester–amide)s from diester‐dicarboxylic acids

Two new aromatic diester‐dicarboxylic acids containing furan rings, namely, benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxyl‐bis‐pyridyl ester‐4,4′‐dicarboxylic acid and benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxyl‐bis‐phenyl ester‐4,4′‐dicarboxylic acid were synthesized by the reaction of benzofuro[2,3‐b]benzofuran‐2,9‐dicarbonyl chloride with 6‐hydroxynicotinic acid and 4‐hydroxybenzoic acid, respectively. These monomers were converted to aromatic copoly(ester–amide)s by reaction with various aromatic diamines via direct polycondensation. Polymers were characterized by FTIR and ¹H NMR spectroscopy, thermogravimetry, viscosity and solubility tests. The inherent viscosity of the polymers was in the range 0.23–0.46 dl g^?1 in dimethyl sulfoxide at 30 °C. They dissolved readily in polar solvents at room temperature. They possess a glass‐transition temperature in the range 210–260 °C and exhibit excellent thermal stability. Copyright © 2004 Society of Chemical Industry     

Synthesis of aromatic poly(ether ketone)s containing C36 aliphatic unsaturated groups in the main chain

Aromatic poly(ether ketone)s (PEKs) were modified with various amount of C36 dimer acid Pripol 1017 obtained from polymerization of unsaturated C18 fatty acids. To obtain modified PEKs, polycondensation was carried out using various dicarboxylic acids with diphenylether at 75°C in phosphorus pentoxide/methanesulfonic acid as condensing agent and solvent. The reduced viscosities of polymers are relatively low, up to 0.13 dL/g. PEK with a structure (molar ratio of aliphatic to aromatic segment: 0.33) is soluble in organic polar solvents and can be cast from a tetrahydrofuran solution with cobalt naphthenate air dryer in order to obtain crosslinked film at room temperature. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1275–1278, 1997     

Synthesis and characterization of new soluble polyamides from an unsymmetrical diamine bearing a bulky triaryl pyridine pendent group

New unsymmetrical diamine monomer containing triaryl pyridine pendent group, 2,4‐diaminophenyl [4‐(2, 6‐diphenyl‐4‐pyridyl) phenyl]ether, was synthesized via aromatic substitution reaction of 1‐chloro‐2,4‐dinitrobenzene with 4‐(2,6‐diphenyl‐4‐pyridyl) phenol, followed by Pd/C‐catalyzed hydrazine reduction. Five Polyamides (PA) were prepared by the phosphorylation polycondensation of different dicarboxylic diacids with the diamine. Inherent viscosities of PAs were in the range 0.51–0.59 g/dL indicating formation of medium molecular weight polymers. The weight and number average molecular weights of a PA, (PA‐d), determined by GPC were 6944 g/mol and 17,369 g/mol, respectively. PAs exhibited glass‐transition temperatures (T_g) in the range 140–235°C. These polymers, essentially amorphous, were soluble in polar aprotic solvents such as DMF, NMP, DMAc, DMSO, pyridine, m‐cresol, and THF. The initial decomposition temperatures (T_i) of PAs, determined by TGA in air, were in the range 300–380°C indicating their good thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of new polyamides and copolyamides containing 6,6'-sulfonediquinoline units

Summary Aromatic polyamides were obtained by the direct polycondensation reaction of a new monomer containing a 6,6'-sulfonediquinoline unit with various aromatic diamines. The polymers were characterised by elemental, infrared, wide angle X-ray diffraction and thermal analysis. The polyamides, possessed inherent viscosities in the range 0.24 – 0.43 dl g⁻¹, 10% weight loss in nitrogen and air above 410°C and glass transition temperatures in the range 170–220°C. The polyamides obtained by reaction with 4,4'-methylenedianiline and 4,4'-sulfonyldianiline were soluble on heating in N-methyl-2-pyrrolidinone and partially soluble in dimethylacetamide. Solubility and thermal properties of copolyamides, prepared from the reaction of 4,4'-oxydianiline with the new monomer and the 4,4'-dicarboxydiphenyl sulfone, were also studied. Received: 5 October 1998/Revised version: 19 April 1999/Accepted: 19 April 1999     

New poly(amide–imide)s syntheses. 17. Preparation and properties of poly(amide–imide)s derived from N-phenyl-3,3-bis[4-(4-aminophenoxy)-phenyl]phthalimidine,trimellitic anhydride,and various aromatic diamines

A dicarboxylic acid ( 1 ) bearing two phthalimide rings was prepared by the condensation of N-phenyl-3,3-bis[4-(4-aminophenoxy)phenyl]phthalimidine and trimellitic anhydride. A new family of poly(amide–imide)s having inherent viscosities of 0.65–1.65 dl/g was prepared by the triphenyl phosphite activated polycondensation of the diimide–diacid 1 with various aromatic diamines in a medium consisting of N-methyl-2-pyrrolidone (NMP), pyridine, and calcium chloride. All the resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP and N,N-dimethylacetamide. The soluble poly(amide–imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range 249–340°C and the 10% weight loss temperatures were above 545°C in nitrogen.     

Synthesis and study of new poly(ester‐imide)s containing triptycene groups

A new triptycene‐containing dicarboxylic acid monomer was successfully synthesized by refluxing the diamine, bis(4‐aminophenoxy)phenyl triptycene with trimellitic anhydride in glacial acetic anhydride. A series of novel thermally stable poly(ester‐imide)s were prepared from dicarboxylic acid, bis(4‐trimellitimido phenoxy)phenyl triptycene with various diols by the direct polycondensation. The polymers were obtained in quantitative yields with inherent viscosities of 0.27–0.74 dL g^?1. The resulting polymers dissolved in N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethyl sulfoxide, and pyridine. These polymers were fairly stable up to a temperature >450°C and lost 10% weight in the range of 477°C and 575°C in nitrogen. The UV–V is absorption spectra revealed that most of the polymers had absorption maxima around 310 and 341 nm. POLYM. ENG. SCI., 54:2252–2257, 2014. © 2013 Society of Plastics Engineers     

Synthesis,characterization, and curing of unsaturated polyamides derived from 2,6-di(4-carboxystyryl)pyridine and 2,6-bis(4-carboxybenzylidene) cyclohexanone

Two new series of heat-curable polyamides were prepared utilizing the unsaturated dicarboxylic acids 2,6-di(4-carboxystyryl)pyridine (DCSP) and 2,6-bis(4-carboxybenzylidene)cyclohexanone (BCBC) as starting materials. They were prepared from the condensation of 4-carboxybenzaldehyde with a half molar amount of 2,6-dimethylpyridine or cyclohexanone, respectively. The dicarboxylic acids reacted with various aromatic diamines, utilizing triphenyl phosphite and pyridine as condensing agents, to yield polyamides. In addition, two model diamides were prepared by condensing the dicarboxylic acids with aniline. Characterization of starting materials, polyamides, and model compounds was accomplished by IR and ¹H–NMR spectroscopy. The curing behavior of polyamides was investigated by DTA. Upon heat-curing, the unsaturated polyamides were crosslinked through their olefinic bonds to afford insoluble, heat-resistant resins. The thermal stability of the resins was evaluated by TGA and isothermal gravimetric analysis (IGA). The cured resins were stable up to 310–322°C in N₂ or air and afforded anaerobic char yield of 57–69% at 800°C.     

Synthesis and identification of organosoluble polyamides bearing a triaryl imidazole pendent: Thermal,photophysical, chemiluminescent,and electrochemical characterization with a modified carbon nanotube electrode

A novel monomer containing a triaryl imidazole pendent group was successfully synthesized by nucleophilic substitution of bisphenol A with 2-(2-chloro-5-nitrophenyl)-4,5-diphenyl-1H-imidazole (I). A series of new polyamides (PAs) with inherent viscosities of 0.95–1.2 dL/g was prepared by direct polycondensation of the diamine with various dicarboxylic acids. These PAs were readily soluble in many organic solvents and gave tough and flexible films by solution casting. These PAs exhibited T_gs between 189 °C and 252 °C, and 10% weight loss temperatures in excess of 400 °C with up to 68% char yield at 600 °C in air. All of the PAs emitted a greenish-yellow light in dilute THF solution, with photoluminescence (PL) quantum yields in the range of 10–25%. The chemiluminescent activity and electrochemical oxidation of the PAs were also investigated.     

Synthesis and properties of polyamides based on 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐hexahydro‐4,7‐methanoindan

A new diamine 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐hexahydro‐4,7‐methanoindan ( 3 ) was prepared through the nucleophilic displacement of 5,5′‐bis(4‐hydroxylphenyl)‐hexahydro‐4,7‐methanoindan ( 1 ) with p‐halonitrobenzene in the presence of K₂CO₃ in N,N‐dimethylformamide (DMF), followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of new polyamides were synthesized by the direct polycondensation of diamine 3 with various aromatic dicarboxylic acids. The polymers were obtained in quantitative yields with inherent viscosities of 0.76–1.02 dl g⁻¹. All the polymers were soluble in aprotic dipolar solvents such as N,N‐dimethylacetamide (DMAc) and N‐methyl‐2‐pyrrolidone (NMP), and could be solution cast into transparent, flexible and tough films. The glass transition temperatures of the polyamides were in the range 245–282 °C; their 10% weight loss temperatures were above 468 °C in nitrogen and above 465 °C in air. © 2000 Society of Chemical Industry     

Synthesis and characterization of novel aromatic poly(amide‐imide)s derived from 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl or 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl and various aromatic diamines

New aromatic diimide‐dicarboxylic acids having kinked and cranked structures, 2,2′‐bis(4‐trimellitimidophenoxy)biphenyl (2a) and 2,2′‐bis(4‐trimellitimidophenoxy)‐1,1′‐binaphthyl (2b), were synthesized by the reaction of trimellitic anhydride with 2,2′‐bis(4‐aminophenoxy)biphenyl (1a) and 2,2′‐bis(4‐aminophenoxy)‐1,1′‐binaphthyl (1b), respectively. Compounds 2a and 2b were characterized by FT‐IR and NMR spectroscopy and elemental analyses. Then, a series of novel aromatic poly(amide‐imide)s were prepared by the phosphorylation polycondensation of the synthesized monomers with various aromatic diamines. Owing to structural similarity, and a comparison of the characterization data, a model compound was synthesized by the reaction of 2b with aniline. The resulting polymers with inherent viscosities of 0.58–0.97 dl g^?1 were obtained in high yield. The polymers were fully characterized by FT‐IR and NMR spectroscopy. The ultraviolet λ_max values of the poly(amide‐imide)s were also determined. The polymers were readily soluble in polar aprotic solvents. They exhibited excellent thermal stabilities and had 10% weight loss at temperatures above 500 °C under a nitrogen atmosphere. Copyright © 2003 Society of Chemical Industry     

Synthesis and characterization of novel soluble pyridine‐containing polyimides based on 4‐phenyl‐2,6‐bis[4‐(4‐aminophenoxy)phenyl]‐pyridine and various aromatic dianhydrides

A new kind of pyridine‐containing aromatic diamine monomer, 4‐phenyl‐2,6‐bis[4‐(4‐aminophenoxy)phenyl]‐pyridine (PAPP), was successfully synthesized by a modified chichibabin reaction of benzaldehyde and a substituted acetophenone, 4‐(4‐nitrophenoxy)‐acetophenone (NPAP), followed by a reduction of the resulting dinitro compound 4‐phenyl‐2,6‐bis[4‐(4‐nitrophenoxy)phenyl]‐pyridine (PNPP) with Pd/C and hydrazine monohydrate. The aromatic diamine was employed to synthesize a series of new pyridine‐containing polyimides by polycondensation with various aromatic dianhydrides in N‐methy‐2‐pyrrolidone (NMP) via the conventional two‐step method, i.e., ring‐opening polycondensation forming the poly (amic acid)s and further thermal or chemical imidization forming polyimides. The inherent viscosities of the resulting polyimides were in the range of 0.79–1.13 dL/g, and most of them were soluble in common organic solvents such as N,N‐dimethylacetamide (DMAc), NMP, and tetrahydrofuran (THF), etc. Meanwhile, strong and flexible polyimide films were obtained, which had good thermal stability, with the glass transition temperatures (T_g) of 268–338°C and the temperature at 5% weight loss of 521–548°C in air atmosphere, as well as outstanding mechanical properties with tensile strengths of 89.2–112.1 MPa and elongations at break of 9.5–15.4%. The polyimides also were found to possess low dielectric constants ranging from 2.53 to 3.11. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 212–219, 2007     

Synthesis and properties of novel aromatic polyamides derived from 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy) phenyl]hexafluoropropane and aromatic dicarboxylic acids

A series of polyamides were synthesized by the direct polycondensation of 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy)phenyl]hexafluoropropane with various commercially available dicarboxylic acids such as terephthalic acid, isophthalic acid, 5‐t‐butyl isophthalic acid, and 2,6‐naphthalene dicarboxylic acid. The synthesized polyamides were soluble in several organic solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and chloroform, and they exhibited inherent viscosities of 0.42–0.59 dL/g. The polyamides exhibited weight‐average molecular weights of up to 26,000, which depended on the exact repeating unit structure. These polyamides showed good thermal stability up to 440°C for a 10% weight loss in synthetic air. The polyamides synthesized from 5‐t‐butyl isophthalic acid and isophthalic acid exhibited glass‐transition temperatures of 217 and 185°C, respectively (by differential scanning calorimetry) in nitrogen. The polyamides synthesized from terephthalic acid and 2,6‐naphthalene dicarboxylic acid showed melting temperatures of 319 and 385°C, respectively. The polyamides films were pale yellow, with tensile strengths of up to 82 MPa, moduli of elasticity of up to 2.3 GPa, and elongations at break of up to 9%, which depended on the exact repeating unit structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 691–696, 2003