Structure and properties of poly(2,5-dimethylterephthalamides)

Six methyl-substituted wholly aromatic polyamides were synthesized from the reaction of 2,5-dimethylterephthaloyl chloride with p-phenylenediamine, its 2,5-dimethyl and 2-methyl derivatives, m-phenylenediamine, or its 2-methyl and 4-methyl derivatives by solution polycondensation at low temperature. The x-ray diffraction diagrams of the polyamides obtained exhibit crystal patterns. Density values range from 1.26 to 1.37 g/cm³. NMR spectra determined in concentrated H₂SO₄ solution are reported. Poly(2,5-dimethylterephthalamides) have lower thermal stability than the corresponding polyterephthalamides. The increase in solubility of polyamide by the introduction of the 2,5-dimethylterephthaloyl linkage is accompanied by a decrease in thermal stability. The effect of methyl substituents on thermal properties and solubility is discussed in terms of the packing of polymeric molecules and the extent of hydrogen bonding of the amide groups.     

Comparison of the properties of the polyimides,polyamides and polyureas derived from 1-[(dialkoxyphosphinyl)-methyl]-2,4- and -2,6-diaminobenzenes and m-phenylenediamine

The physical and thermal properties of various phosphorus-containing polyimides, polyamides and polyureas based on 1-[(dialkoxyphosphinyl)methyl]-2,4- and -2,6-diaminobenzenes as well as of the corresponding common polymers derived from m-phenylenediamine were compared and correlated with their chemical structure. Differential scanning calorimetry (DSC) measurements showed that the introduction of the (dialkoxyphosphinyl) methyl groups in the polymers converted their endothermic pyrolysis under anaerobic conditions to exothermic or reduced the heat adsorbed during their pyrolysis. Thermogravimetric analysis (TGA) showed that the thermal stability of the polymers and the char yield formed during their pyrolysis were in the order polyureas < polyamides < polyimides. All phosphorylated polymers showed a lower degree of polymerization, a lower polymer decomposition temperature and formed higher char residue on pyrolysis than the corresponding common polymers.     

Polyamides based on diamines and N,N′-dimethyldiamines derived from biphenol

Aromatic-aliphatic polyamides containing a biphenyl mesogen were prepared by both interfacial and solution polymerization reactions. Substitution of the amide nitrogen with methyl groups yielded polymers with significantly different properties than the unsubstituted polyamides. The methyl-substituted polyamides had improved thermal stability, significantly lower meltin temperatures, and greater solubility in common solvents. Copolyamides were also synthesized which contained different flexible spacer units that varied in the number of methylene groups. No evidence for the presence of liquid crystalline phases could be obtained in either the unsubstituted polyamides or polyamides containing N-methylated amide units. © 1994 John Wiley & Sons, Inc.     

Synthesis and studies of homopolyamides based on 2,4-bis(6-chlorocarbonyl-2-naphthyloxy)-6-(4-methyl-1-piperazinyl)-s-triazine

Abstract  

Ten homopolyamides have been synthesized by polycondensation of the monomer 2,4-bis(6-chlorocarbonyl-2-naphthyloxy)-6-(4-methyl-1-piperazinyl)-s-triazine and different diamines such as 4,4′-biphenyldiamine, 4,4′-diaminobenzanilide, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfonamide, 2,4-diaminotoluene, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and ethylenediamine. All polyamides were characterized by solubility, density, viscosity measurements, IR, NMR spectroscopy, and thermogravimetric analysis. The products were found to possess high thermal stability.     

Synthesis and properties of polyamides of p-phenylenedioxydiacetic acid

Several polyamides of p-phenylenedioxydiacetic acid (PDDA) were synthesized by the low-temperature solution polycondensation techniques. Six different diamines were condensed independently with p-phenylenedioxydiacetyl chloride (PDC) in a mixture of N-methyl pyrolidone (NMP) and hexamethyl phosphoramide (HMPA). The polymers were obtained in 80–95% yield and possessed inherent viscosities in the range 0.32–0.81 dL/g. The polymers were characterized by infrared (IR) and H¹-NMR spectra. The solubility, density, crystallinity, and thermal stability of the polyamides were also determined. A model diamide (MDA-1) was also synthesized from aniline and PDC to confirm the formation of polyamides from diamines.     

多取代芳香类聚酰胺的合成

芳香聚酰胺具有优异的热稳定性,但在溶剂中的溶解性能较差。人们发现在聚酰胺中的苯环上引进甲基取代基是改善聚合物溶解性能的一种有效的途径,Takatsuka等曾合成了一系列一取代和二取代甲基的芳香聚酰胺,聚合物的溶解性有较大的改善。但尚未见关于三甲基取代聚合物的合成报道。     

Aromatic rigid chain copolymers. I. Synthesis,structure, and solubility of phenyl-substituted para-linked aromatic random copolyamides

Four 2,5-biphenylene based difunctional condensation monomers, such as 2,5-diphenyldicar-boxylic acid or phenylterephthalic acid (PTA), 2,5-bis(carbonylimino-4-benzoic acid)biphenyl (2,5-BCIBABP), 2,5-diaminobiphenyl hydrochloride (2,5-DABP.HCl) and 2,5-bis(iminocarbonyl-4-benzoic acid)biphenyl (2,5-BICBABP), have been synthesized and characterized. These monomers were polymerized in combination with terephthalic acid (TA) and p-phenylenediamine (PPD) via the phosphorylation reaction to prepare a series of phenyl-substituted random copolyamides having all amide groups attached to para-positions of the benzene rings. All the copolyamides have been characterized by solubility, solution viscosity, and by differential scanning calorimetry (DSC). Some of these copolyamides have unusual solubility in organic solvents such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidinone (NMP) containing dissolved lithium chloride. A few copolyamides were tested for lyotropic behavior and found to form anisotropic solutions at critical concentrations in organic solvents. A randomly distributed unsymmetrical phenyl substituent on the benzene ring of para-oriented wholly aromatic polyamides dramatically changes the solubility and melting point. The phenyl substituent on a terephthalic acid unit is more efficient in decreasing melting point and increasing solubility in organic solvents of aromatic polyamides than the one on a p-phenylenediamine unit. However, the former also introduces a more flexible link in the extended polyamide chain.     

Optically high transparency and light color of organosoluble polyamides containing trifluoromethyl and kink diphenylmethylene linkage

New polyamides were prepared directly from a diamine, bis[4‐(2‐trifluoromethyl 4‐aminophenoxy)phenyl] diphenylmethane, containing an electron‐withdrawing trifluoromethyl group and a kink diphenylmethylene linkage with various aromatic dicarboxylic acids having inherent viscosities ranging from 0.66 to 0.83 dL g^?1. All the polyamides showed outstanding solubility and could be easily dissolved in amide‐type polar aprotic solvents (e.g., N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, and N,N‐dimethylformamide) and even dissolved in less polar solvents (e.g., pyridine, cyclohexanone, and tetrahydrofuran). The dielectric constants of the polyamide films were 3.37–3.87 (100 KHz) and decreased with an increase in the frequency, which ranged from 1 Hz to 100 KHz. A low coefficient of thermal expansion for the polyamides was observed in the range of 54–78 ppm/°C (by thermomechanical analysis). These polyamides showed excellent thermal stability, and the 10% weight loss temperatures were in the range of 484–507 °C in an atmosphere of nitrogen. The polymers had an initial modulus of 1.8–2.2 GPa. The polyamides with kink and electron‐withdrawing trifluoromethyl units afforded light‐color polymer films with high transmittance in the visible region (400–700 nm), and their cutoff wavelength was lower than 362 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4559–4569, 2005     

Synthesis and characterization of N‐benzoylated wholly aromatic polyamides from 4,4′‐oxydianilinobis(benzimidoyl) chloride and aromatic dicarboxylic acids

A novel type of polyamides, N‐benzoylated wholly aromatic polyamides, were synthesized by low‐temperature solution polycondensation of a new aromatic bis(imidoyl) chloride, 4,4′‐oxydianilinobis(benzimidoyl) chloride, with aromatic dicarboxylic acids, 4,4′‐oxydibenzoic acid and isophthalic acid. Compared with the conventional all aromatic polyamides and also N‐phenylated wholly aromatic polyamides, these N‐benzoylated aramides exhibit better solubility in organic solvents, lower glass transition temperatures and thermal stability.     

Synthesis and properties of novel aromatic polyamides based on 4-aryl-2,6-bis(4-chlorocarbonylphenyl) pyridines

A facile synthesis of three new diacid chlorides containing pyridine ring bearing aromatic type pendant groups on its 4-position is described. The monomers were characterized by FTIR, 1HNMR, mass spectroscopies and elemental analysis. Polycondensation reactions of the prepared diacid chlorides with different commercially available diamines resulted in the preparation of novel polyamides. Optimal conditions for polyamidations were obtained via study of the model compounds. The polymers were characterized by FTIR, 1HNMR, and elemental analysis and their physical properties including solution viscosity, solubility properties, thermal stability and thermal behavior were studied as well. The polyamides show excellent thermal stability and solubility in polar aprotic solvents.     

Novel two-step synthesis of polybenzothiazoles via precursor polyamides from 2,5-bis(isopropylthio)-1,4-phenylenediamine and aromatic dicarboxylic acid chlorides

A novel two-step method for the synthesis of polybenzothiazoles has been developed starting from 2,5-bis(isoprophylthio)-1,4-phenylenediamine and aromatic dicarboxylic acid chlorides. The low-temperature solution polycondensation of these monomer pairs in N-methyl-2-pyrrolidone afforded the aromatic polyamides with pendant isopropylthio groups having inherent viscosities in the range of 0.8 and 2.4 dL/g. The soluble precursor polyamides were subjected to thermal cyclization to the corresponding polybenzothiazoles along with the elimination of propylene and water. The resulting polymers were also characterized.     

Mass spectrometry of imidazole-4(5)-carboxaldehyde and some 1-methyl and nitro derivatives

The mass spectra of imidazole-4(5)-carboxaldehyde, its two 1-methyl derivatives, 4(5)-nitroimidazole, 5(4)-nitroimidazole-4(5)-carboxaldehyde and 1-methyl-5-nitroimidazole-4-carboxaldehyde are presented and discussed in comparison with those of other imidazole-carboxaldehydes and nitroimidazoles earlier reported. The imidazole-carboxaldehydes and their 1-methyl derivatives exhibit the characteristic fragmentation of aromatic aldehydes, and differences between the isomers can be observed. The nitroimidazoles show the fragmentation typical of aromatic nitrocompounds. In the o-nitroimidazole-carboxaldehydes, the typical losses of aldehydes do not occur, but primary ortho effects between the formyl and nitro groups give rise to important fragmentation routes. In their 1-methyl derivatives, the presence of the methyl group adjacent to the nitro group originates additional double and secondary ortho effects. For some of these transformations, fragmentation mechanisms are proposed.     

Effect of methyl substituents on permeability and permselectivity of gases in polyimides prepared from methyl-substituted phenylenediamines

Permeability and solubility coefficients for H₂, CO₂, O₂, CO, N₂, and CH₄ in polyimides prepared from 6FDA and methyl-substituted phenylenediamines were measured to investigate effects of the substituents on gas permeability and permselectivity. The methyl substituents restrict internal rotation around the bonds between the phenyl rings and the imide rings. The rigidity and nonplanar structure of the polymer chain, and the bulkiness of methyl groups make chain packing inefficient, resulting in increases in both diffusion and solubility coefficients of the gases. Polyimides from tetramethyl-p-phenylenediamine and trimethyl-m-phenylenediamine display very high permeability coefficients and very low permselectivity due to very high diffusion coefficients and very low diffusivity selectivity, as compared with the other polyimides having a similar fraction of free space. This suggests that these polyimides have high fractions of large-size free spaces.     

Aromatic polyisophthalamides with N-benzylidene pendant groups

A new series of modified polyisophthalamides bearing N-benzylidene pendant groups was prepared by reacting various aromatic diamines with 5-(N-benzylidene) isophthalic acid. The latter was synthesized from the reaction of 5-aminoisophthalic acid with benzaldehyde and characterized by IR and ¹H-NMR spectroscopy. Triphenyl phosphite and pyridine was used as condensing agents for preparing polyamides. In addition, the corresponding unsubstituted polyisophthalamides were prepared under identical experimental conditions for comparative purposes. Characterization of modified polyamides was accomplished by IR as well as inherent viscosity measurements. They showed a slightly lower solubility in various media than the corresponding unsubstituted polyamides. The cured modified polyamides displayed significantly higher thermal stability than the cured unsubstituted polyamides. They were stable up to 355–308°C in N₂ or air and afforded anaerobic char yield of 66–61% at 800°C. © 1992 John Wiley & Sons, Inc.     

Synthesis and characterization of polyamides obtained from tartaric acid and L-lysine

Two sets of AA · BB-type polyamides (PLyTA) were synthesized from natural compounds L-lysine and D- or L-tartaric acid via the active ester polycondensation method. The carboxyl and hydroxyl side groups were orthogonally protected as methyl ester and methyl ether, respectively. Direct reaction of methyl L-lysinate dihydrochloride with bis(pentachlorophenyl) di-O-methyl tartaric acid led to the aregic polyamide ar-PLyTA, whereas isoregic (ir-PLyTA) and syndioregic (sr-PLyTA) polyamides were obtained by polycondensation of specifically designed amide–aminoacid and amide–diamine monomeric precursors, respectively. These polyamides have intrinsic viscosities in the 0.50–0.76 dl g⁻¹ range, display optical activity, and are readily soluble in chloroform. They start to decompose well above 200 °C and display glass-transition temperatures at 100–105 °C. DSC and X-ray diffraction results indicated that these polyamides are not crystalline but they seem to adopt a partially ordered phase. No differences in properties other than optical rotation were observed between PLyTA made of D- and L-tartaric acid.     

Synthesis and characterization of polyamides containing pendant pentadecyl chains

A new aromatic diacid monomer viz., 4-(4′-carboxyphenoxy)-2-pentadecylbenzoic acid was synthesized starting from cardanol and was characterized by FTIR, ¹H- and ¹³C NMR spectroscopy. A series of new aromatic polyamides containing ether linkages and pendant pentadecyl chains was prepared by phosphorylation polycondensation of 4-(4′-carboxyphenoxy)-2-pentadecylbenzoic acid with five commercially available aromatic diamines viz., 1,4-phenylenediamine, 4,4′-oxydianiline, 4,4′-methylenedianiline, 1,3-phenylenediamine, and 4,4′-(hexafluoroisopropylidene)dianiline. Inherent viscosities of the polyamides were in the range 0.45-0.66 dL/g in N,N-dimethylacetamide at 30 ± 0.1 °C. The introduction of ether linkages and pendant pentadecyl chains into polyamides led to an enhanced solubility in N,N-dimethylacetamide and 1-methyl-2-pyrrolidinone at room temperature or upon heating. The polyamides could be solution-cast into tough, flexible and transparent films from their N,N-dimethylacetamide solution. Wide angle X-ray diffraction patterns exhibited broad halo indicating that the polymers were essentially amorphous in nature. X-Ray diffractograms also displayed a diffuse to sharp reflection in the small-angle region (2θ = ∼2-5°) for the polyamides characteristics of formation of loosely to well-developed layered structure arising from packing of flexible pentadecyl chains. The glass transition temperature observed for the polyamides was in range 139-189 °C. The temperature at 10% weight loss (T₁₀), determined by TGA in nitrogen atmosphere, of the polyamides was in the range 425-453 °C indicating their good thermal stability.     

Effect of N-methyl substitution on the thermal decomposition processes in aliphatic–aromatic polyamides

The thermal decomposition processes of two polyamides, derived from succinic acid and two aromatic diamines, were studied by direct pyrolysis mass spectrometry. Fast atom bombardment (FAB) mass spectrometry has been also used in order to provide additional information for the elucidation of the thermal degradation mechanism of the polymers investigated. FAB mass spectra, obtained by introducing in the FAB ion source the solid residues from polymer pyrolysis performed in thermogravimetric experiments, allowed the detection of diagnostic compounds up to about 1600 amu. Our results indicate that the thermal stability of the N-methyl-substituted polyamide is higher than that of the unsubstituted polyamide. The difference in the thermal degradation mechanism accounts for the difference in the thermal stability of the two polyamides. In fact, the unsubstituted polyamide decomposes via an intramolecular exchange and a concomitant N? H hydrogen transfer process with formation of compounds with amine and/or succinimide end groups. Instead, the N-methyl-substituted polyamide decomposes via an α C? H hydrogen transfer process from the methyl group to the nitrogen atom with formation of compounds with amine and/or 2,5-piperidinedione end groups.     

A stereochemical investigation of 2-methyl- and 2,5-dimethyl-3-phenyl-1,3-oxazolidines using NMR

The stereochemical properties of two 2-methyl-3-phenyl-1,3-oxazolidines and two of its 5-methyl substituted and four of its 2,5-dimethyl substituted derivatives have been investigated by pmr and cmr methods. The compounds of 2,5-dimethyl-3-phenyl-1,3-oxazolidines exist in isomeric cis and trans forms at the two methyl groups on the heterocyclic ring.     

Soluble and fusible polyamides and polyimides containing pyrazoline moieties and their crosslinking to heat-resistant resins

3-(4-Aminophenyl)-5-(3-aminophenyl)-2-pyrazoline as well as the 1-acetyl- or 1-benzoyl-substituted derivatives of this compound were synthesized and used for preparing a new series of polyamides and polyimides. Characterization of polymers was accomplished by inherent viscosity, ¹H-NMR, ¹³C-NMR, x-ray, DTA, TMA, TGA, and isothermal gravimetric analysis. The properties of polymers were correlated with their chemical structures. They were amorphous or microcrystalline and soluble in polar aprotic solvents, CCl₃COOH, and m-cresol. The polyamides showed an excellent solubility being soluble even in o-dichlorobenzene, 1,2-dichloroethane, and chloroform. The polymers displayed T_g at 127–163°C and softening at 150–195°C. The polyamide bearing unsubstituted pyrazoline moieties was remarkably more hydrophilic than those containing 1-acetyl- or 1-benzoyl-substituted pyrazoline segments. Upon curing, crosslinked polymers were obtained and their thermal stability was evaluated. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1353–1361, 1997     

Model compounds and polymers with quinoxaline units

Tetra- and heptanuclear N-heterocycles, their dimers and their polymers have been prepared by condensation of o-phenylenediamine or 3,3'-diaminobenzidine with 2,3-dihydroxyquinoxaline, 2,3,2,3'-tetrahydroxy-6,6'-bisquinoxaline, or 2,3,7,8-tetrahydroxy-1,4,6,9-tetraazaanthracene in polyphosphoric acid, or with the O-phenyl derivatives of the latter three compounds in phenol. The condensation products are highly colored compounds with characteristic absorption spectra. The polymers show good thermal stability.