Diimide-diacid Monomer Research Articles

Synthesis and Properties of Polyamide 6 Random Copolymers Containing an Aromatic Imide Structure.

In order to adjust the properties of polyamide 6 (PA6) and expand its application, a new strategy of introducing an aromatic imide structure into the PA6 chain through the random copolymerization method is reported. The diimide diacid monomer was first synthesized by the dehydration and cyclization of pyromellitic dianhydride and 6-aminocaproic acid before it reacted with 1,6-hexamethylene diamine to form poly(amide imide) (PAI) salt, and finally synthesized PA6/PAI random copolymers containing an aromatic imide structure by the random copolymerization of ε-caprolactam and PAI salt. The introduction of an aromatic imide structural unit into the PA6 chain could have a great influence on its properties. As the content of PAI increases, the crystallinity (Xc) and melting temperature (Tm) of the PA6/PAI random copolymer gradually decrease, but its glass transition temperature (Tg) increases obviously. When the PAI content is 20 wt%, the copolymer PA6/PAI-20 has the best comprehensive performance and not only has high thermal stabilities but also excellent mechanical properties (high strength, high modulus, and good toughness) and dielectric properties (low dielectric constant and dielectric loss). Moreover, these properties are significantly superior to those of PA6. Such high-performance PA6 random copolymers can provide great promise for the wider applications of PA6 materials.

Synthesis and Characterization of Bio-Based Poly(amide imide)s Derived from 11-Aminoundecanoic Acid and 1,10-Diaminodecane

Three diimide diacid (DIDA) monomers possessing different rigid groups (phenyl, biphenyl and diphenyl ether group) between two imide rings were prepared through the dehydration cyclization reaction of 11-aminoundecanoic acid and aromatic dianhydride. These DIDA monomers were polymerized with 1,10-diaminodecane to produce bio-based poly(amide imide)s (PAIs) by the ecofriendly and low-cost two-step polymerization method. All the PAIs have high thermal stabilities, and their initial thermal decomposition temperatures are above 400 °C at 5% weight loss. When the rigid group between two imide rings is changed from phenyl to diphenyl ether group, the glass transition temperature of PAI shows a decreasing trend from 54.7 °C to 42.4 °C, the tensile strength also reduces from 62.4 MPa to 49.5 MPa, but elongation at break increases from 3.7% to 6.8%. Moreover, the PAI with phenyl group between two imide rings is a semicrystalline polymer, while the PAI with biphenyl or diphenyl ether group is an amorphous polymer. It is a viable way to regulate the properties of PAIs by changing the structure of rigid group between two imide rings. Such bio-based PAIs with high thermal stabilities, low glass transition temperatures and good mechanical strength will provide great promise for their wider applications.

Novel fluorinated long linear segment hyperbranched polyimides bearing various pendant substituents for applications as optical materials

Four novel hyperbranched polyimides (HBPI) (a-d) with long linear segments have been synthesized from a triamine monomer and a series of diimide-diacid monomers (I-IV). All of these HBPIs exhibit good solubility as well as excellent thermal stability. As a result of the presence of long linear segments in the hyperbranched structure, the HBPI films exhibit better flexibility than previously reported polymers, with an elongation at break of 6.7–7.2%. Each of these HBPIs has a cutoff wavelength that is shorter than 356 nm. In addition, all of the HBPIs exhibit a high optical transmittance at 800 nm. The refractive indices of the HBPIs were investigated, and the values were found to be in the range of 1.5631–1.5727 at a wavelength of 650 nm, and the refractive index by copolymerization of HBPI is adjustable. Furthermore, the HBPI films obtained via spin-coating presented extremely low birefringence values (0.0013–0.0021), and low NIR absorption losses of 1310 and 1550 nm at the communication windows.

Synthesis, Characterization and Structure–Property Relationships of Processable Poly(amide-imide)s Containing Novel Tetraphenylthiophene-Thiazole Diimide-Diacid (TPTPThDIDA) Moiety

The main objective of this research was to study the structure–property relationships to high performance polymers with thermal stability, solubility and viscosity. Hence, a series of novel poly(amide-imide)s (PAIs) was synthesized from a tetraphenylthiophene-thiazole containing diimide-diacid(TPTPThDIDA) monomer with commercially available various aromatic diamines by using Yamazaki’s direct phosphorylation reaction. The resulting PAIs were obtained in high yields and inherent viscosities in the range of 0.86–0.96 dL/g. The reinforcement of the heterocyclic thiazole ring unit on the properties of these PAIs was studied by comparison of the corresponding polymers containing tetraphenylthiophene groups. The PAIs exhibited excellent solubility and good thermal stability. PAIs showed high glass-transition temperatures in the range of 267 °C–302 °C. Thermogravimetric analysis of the PAIs indicated a 10% weight loss (T10) in the temperature range of 609–736 °C and char yields at 900 °C under nitrogen atmosphere in the range of 73–80% depending on the diamine monomer used for the synthesis PAIs. The LOI of all poly(amide-imide)s were more than 29, thus such type polymers of can act as flame-retardant materials.

New poly(amide-imide)s with trifluoromethyl and chloride substituents: Synthesis, thermal, dielectric, and optical properties

Two novel fluorinated diimide-diacid monomers, [2,2′-(4,4′-(4′-chloro-3′-(trifluoromethyl)biphenyl-2,5-diyl)bis(oxy)bis(3-(trifluoromethyl)-4,1-phenylene))bis(1,3-dioxoisoindoline-5-carboxylic acid)] (III) and [2,2′-(4,4′-(3′,5′-bis(trifluoromethyl)biphenyl-2,5-diyl)bis(oxy)bis(3-(trifluoromethyl)-4,1-phe-nylene))bis(1,3-dioxoisoindoline-5-carboxylic acid)] (IV), were respectively designed and synthesized viathe reactions between the diamine (I or II) and two molar equivalents of trimellitic anhydride. Based on these two diimide-diacids, two families of novel poly(amide-imide)s (PAIs) (IIIa–IIIe and IVa–IVe) bearing different trifluoromethyl groups were prepared by directly polymerizing diimide-diacids with a series of aromatic diamines (a–e). All of the PAIs exhibited high glass transition temperatures (Tgs, 236–268°C), excellent thermal stability (only 5% weight loss at 493–542°C under nitrogen) and good solubility in various organic solvents since the bulky pendant groups were introduced. The cast films of these PAIs (thickness=80–90μm) had excellent optical transparency (70–83% at 450nm, 85–87% at 550nm and 88–89% at 800nm) and low dielectric constants (2.62–2.92 at 1MHz). In addition, the spin-coated films of these PAIs presented very low birefringence values the minimum of which was 0.0073 at 650nm. These spin-coated films also exhibited very weak absorption at the near-infrared communication wavelengths of 1310 and 1550nm.

Molecular design and synthesis of thermotropic liquid crystalline poly(amide imide)s with high thermal stability and solubility

Abstract A series of thermotropic liquid crystalline poly(amide imide)s (PAIs) with well-defined structure were prepared by the Yamazaki-Higashi phosphorylation method. To obtain the target polymers, several diimide diacid monomers (DIDAs) as mesogenic units were synthesized by the dehydration cyclization of aromatic anhydride with aliphatic 11-aminoundecanoic acid (AU). The chemical structure of these DIDAs and PAIs was confirmed via Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. Thermotropic liquid crystalline characteristics of the DIDAs and PAIs were investigated by differential scanning calorimetry (DSC), polarizing light microscopy (PLM) and X-ray diffraction (XRD) analysis. Encouragingly, all of these liquid crystalline PAIs exhibited good thermal stability, in which the decomposition temperatures are much higher than the melting temperatures of PAIs. Furthermore, the liquid crystalline PAIs can be dissolved into some common solvents such as dimethyl sulfoxide (DMSO) and m-cresol, which indicates these liquid crystalline PAIs could be processed not only by melting-processing but also by solution spin-coating.

Synthesis of electroactive and electrochromic poly(amide-imide)s containing diphenylpyrenylamine moieties

A novel dicarboxylic acid monomer bearing two built-in imide rings, namely N,N-bis(4-trimellitimidophenyl)-1-aminopyrene, was synthesized from the condensation of N,N-di(4-aminophenyl)-1-aminopyrene and two equivalent amount of trimellitic anhydride. New poly(amide-imide)s (PAIs) with diphenylpyrenylamine segments were prepared by the direct phosphorylation polyamidation reactions from the newly synthesized diimide-diacid monomer with two different aromatic diamines or from N,N-di(4-aminophenyl)-1-aminopyrene with four different imide ring-preformed dicarboxylic acids. All the polymers were readily soluble in many organic solvents and could be solution-cast into tough and flexible polymer films. These PAIs showed glass-transition temperatures (T gs) in the range of 211–352 °C, and they did not show significant weight-loss before 500 °C. Cyclic voltammograms of the PAI films cast onto the indium-tin oxide (ITO)-coated glass substrate revealed reversible electrochemical oxidation processes accompanied with strong color changes from the pale yellow neutral state to the purplish blue oxidized state and the orange reduced state, respectively. Incorporating the diphenylpyrenylamine unit on the amide side of PAIs led to lower oxidation potentials and higher redox reversibility and, thus, better electrochromic performance such as high coloration efficiency, fast switching speed, and high electrochromic stability.

Synthesis and structure–property relationships of novel thiazole‐containing poly(amide imide)s with high refractive indices and low birefringences

AbstractThe primary objective of this study was to investigate the structure–property relationships in high‐performance polymers with high refractive indices and low birefringences. A series of novel poly(amide imide)s (PAIs) were synthesized from a thiazole‐containing diimide–diacid monomer and various aromatic diamines. The influence of the pendant phenyl substituents on the optical properties of these PAIs was studied by comparison with the analogous polymers containing methyl groups. The PAIs exhibited excellent solubility and good thermal stability. The optical transmittances of the PAI films at 450 nm were higher than 75%. The combination of the thiazole units, thioether linkages and pendant phenyl rings provided the PAIs with high average refractive indices of 1.7361–1.7536 and low birefringences of 0.0066–0.0097 at 632.8 nm. © 2014 Society of Chemical Industry

Synthesis and characterization of novel nanostructured, organosoluble, thermally stable and wholly aromatic poly(amide-imide)s from a new diimide-diacid monomer by direct polycondensation

In the present work, a new diimide-diacid monomer bearing pyridine rings was prepared. A series of novel nanostructured, organosoluble, thermally stable and wholly aromatic poly(amide-imide)s (PAIs) were synthesized from diimide-diacid, by direct polycondensation with various aromatic diamines in N-methyl-2-pyrrolidone using triphenyl phosphite and pyridine as a condensing agent. The nanostructured PAIs were achieved in good yields and possessed moderate inherent viscosities in the range of ηinh = 0.37–0.51 dL g−1. The synthesized polymers were characterized with FT-IR, 1H-NMR, UV–vis spectroscopy, elemental analysis, X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and thermogravimetric analysis (TGA) techniques. All of the PAIs were amorphous in nature, were readily soluble in many organic solvents and could be solution cast into tough and flexible films. These polymers exhibited strong UV–vis absorption in the range of 294–311 nm in solution and in films. According to TGA data, these polymers exhibited initial decomposition temperature in the range of 396–433 °C, temperature of 10% weight loss from 446 to 537 °C, char yields more than 75% at 700 °C in nitrogen atmosphere and can be classified as self-extinguishing polymers. FE-SEM results show that, these nanostructured PAIs have spherical and cylindrical beads and the particle size is around 35–90 nm.

New triphenylamine-based poly(amine-imide)s with carbazole-substituents for electrochromic applications

A new carbazole-derived triphenylamine-containing diimide-diacid monomer (5), 4,4′-bis(trimellitimido)-4″-N-carbazolytriphenylamine, is prepared by the condensation of 4,4′-diamino-4″-N-carbazolytriphenylamine (4) and two molar equivalents of trimellitic anhydride (TMA). A series of new poly(amide-imide)s (PAIs) 7a–7d with carbazole-substituted triphenylamine units are prepared by direct polymerization from the new diimide-diacid (5) and various aromatic diamines (6a–6d). The PAIs shows high glass transition temperature between 269 and 297°C, and high 5% weight loss temperature between 526 and 561°C under nitrogen environment. Cyclic voltammograms of the PAIs films, which are casted onto the indium–tin oxide (ITO)-coated glass substrate, exhibit two reversible oxidation redox couples at 1.05–1.08V and 1.38–1.46V under an anodic sweep. The PAI-7a film reveals excellent stability of electrochromic characteristics for the radical cations generated, changing color from original pale yellowish neutral form to the green and then to dark blue oxidized forms. Furthermore, the anodically coloring of PAI-7a shows high coloration efficiency (CE=205cm2/C), high contrast of optical transmittance change (ΔT=80% at 776nm) and long-term redox reversibility.

Synthesis and characterization of phosphorus containing aromatic poly(amide-imide)s copolymers for high temperature applications

A series of novel thermally stable poly(amide-imide)s (PAIs) based on non-coplaner diimide-diacid (DIDA) monomer is synthesized. These polymers are characterized by elemental analysis, FT-IR, 1H-NMR, 13C-NMR and 31P-NMR spectroscopic techniques and their physical and thermal properties are also studied. Four different dianhydrides pyromellitic anhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA)/1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA)/4,4′-oxydiphthalic anhydride (ODPA) and amino acid l-tryptophan are used to synthesize DIDA. The polymerization of DIDA with phosphorus containing triamines having phenyl moieties gives poly(amide-imide)s. The synthesized polymers are obtained in high yield and possessed inherent viscosity in the range 0.66–0.98 dL/g. These polymers display higher solubility in polar aprotic solvents, such as DMSO, NMP and DMF. In addition, the absorption edge values (λ o) obtained from their UV curves are determined, and all the resulting poly(amide-imide)s films exhibited high optical transparency. The glass transition temperature (T g) of these polymers is recorded in the range 211–265 °C, initial decomposition temperature in excess of 435 °C and char yield at 800 °C in nitrogen ranged from 52 to 70 %. Wide angle X-ray diffraction showed that all the polymers are almost amorphous.

Synthesis of Diimide-Diacid Monomers and Poly(amideimide)s: Effects of Flexible Linkages and Pendant Hexafluoroisopropylidine Unit on Processability, Thermal Stability and Electrical Properties

Two diimide-diacid monomers N,N′-bis(4-carboxypheny-4-oxyphenyl)oxydiphthalimide and N,N′-bis(4-carboxyphenyl-4-oxyphenyl)4,4′-(hexafluoroisopropylidene)diphthalimide were synthesized and characterized by IR and 1H-NMR. A series of poly(amideimide)s were prepared by direct polycondensation of diimide-diacids with aromatic diamines through phosphorylation reaction. The poly(amideimide)s were characterized by IR, XRD, TGA, DSC, solution viscosity, solubility studies and electrical properties. X-ray diffraction studies indicate that the poly(amideimide)s were amorphous. Poly(amideimide)s were soluble in common organic solvents and exhibit excellent thermal stability. The PAIs have electrical insulation character and can be used in insulation of electrical items operating at elevated temperatures.

Synthesis of new diacid monomers and poly(amide-imide)s: study of structure–property relationship and applications

Two diimide-diacid monomers 4,4′-bis[4″-(trimellitimido)phenyl isopropylidene-4″′-phenoxy]diphenyl sulfone and 4,4′-bis[4″-(trimellitimido)phenylisopropylidene-4″′-phenoxy] were synthesized. The structures of the monomers were characterized by FT-IR and 1H-NMR spectroscopy. A series of novel poly(amide-imide)s were prepared from this two diacids and aromatic diamines through phosphorylation reaction. The PAIs were characterized by FT-IR, 1H-NMR, XRD, TGA, and DSC, solution viscosity, solubility test and electrical properties. Poly(amide-imide)s showed excellent solubility due to the presence of flexible groups and isopropylidene unit in the polymer backbone. They also exhibited good thermal stability and the temperatures at which 10% weight loss occurred in the range 385–465 °C. These PAIs found to have a dielectric constant in the range 3.25–4.20 at 10 kHz and have excellent electrical insulation character and can be used as insulation materials for electrical items operating at elevated temperatures.

Synthesis and Characterization of Chiral Poly(Amide-Imide) Containing L-Alanine

A novel chiral poly(amide imide) containing L-alanine was synthesized by direct polycondensation reaction of newly synthesized N,N’-(4,4’-diphthaloyl)-bis-L-alanine diacid with 4,4’-diaminodiphenyl ether in a medium consisting of N-methyl-2-pyrrolidone (NMP), triphenylphosphite (TPP), calcium chloride (CaCl2), and pyridine. The new chiral diimide-diacid monomer was synthesized by direct reaction of 3,3’-4,4’-Biphenyl tetracarboxylic acid dianhydride with L-alanine in acetic acid under refluxing conditions. The resulting compounds were obtained in quantitative yields and high purity. The synthetic diacid monomer was characterized by elemental analysis, 1H-NMR spectroscopy, FT-IR techniques and specific rotation, the obtained polymer was characterized by FTIR techniques, specific rotation and solubility testing.

Heat-resistant and soluble fluorinated poly(amide imide)s based on non-coplanar ortho-linked diimide-dicarboxylic acid

A series of novel fluorinated heat-resistant poly(amide imide)s (PAIS) based on non-coplanar diimide-diacid monomer (DIDA) were synthesized and characterized. The poly(amide imide)s were obtained in high yields and possessed inherent viscosities in the range of 0.47–0.91 dL g −1. All of the polymers were amorphous in nature, showed outstanding solubility and could be readily soluble in common organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidinoned, dimethyl sulfoxide, N,N-dimethylformamide, pyridine and tetrahydrofuran. Glass transition temperatures were in the range of 221–263 °C, as determined by differential scanning calorimetry. Degradation temperatures for 10% weight loss occurred all above 520 °C and char yields was more than 50% at 700 °C in nitrogen atmosphere. Moreover, these PAIs possessed low refractive indexes ( n = 1.58–1.59), birefringence (Δ n = 0.008–0.013), and dielectric constants ( ɛ ≈ 2.5) due to the trifluoromethyl pendent groups and ortho-catenated aromatic rings that interrupt chain packing and increase free volume.

Novel heat-resistant and organosoluble poly(amide-imide)s containing laterally-attached phenoxy phenylene groups

In this research a new diimide-diacid monomer, 2,2′-bis(4-phenoxyphenyl)-4,4′-bis( N-trimellitoyl)diphenyl ether ( BPDPE) containing two laterally-attached phenoxy phenylene groups was prepared by the reaction of 2,2′-bis[( p-phenoxy phenyl)]-4,4′-diaminodiphenyl ether ( PPAPE) with trimellitic anhydride in refluxing glacial acetic acid. Ether-hinged wholly aromatic poly(amide-imide)s with limited viscosity number values of 0.61–0.87 dL g −1 were prepared by triphenyl phosphate (TPP)-activated polycondensation of BPDPE with diamines including PPAPE and 4,4′-diaminodiphenyl ether ( DADPE). For comparative purposes, reference poly(amide-imide)s were also prepared by reacting diimide-diacid monomer lacking phenoxy phenylene lateral groups namely 4,4′-bis( N-trimellitoyl)diphenyl ether ( BTDPE) with the same diamines under similar conditions. A model compound MODEL was also synthesized by the reaction of BTBPE with two mole equivalents of aniline to compare the spectral characteristics results. Number and weight average molecular weights ( M ¯ n and M ¯ w ) were determined by gel permeation chromatography (GPC) technique. The phenoxy phenylene-containing poly(amide-imide)s (all, except that of resulted from BTDPE and DADPE) had excellent organosolubility in common polar solvents. A low crystallinity extent was only observed using their wide-angle X-ray diffractograms (WAXD). A qualitative study showed the prepared polymers could also be cast into optically-transparent and flexible thin films. The ether-containing lateral groups attached to the ether-hinged macromolecular main chains had no substantial diminishing effect on the thermal stability of these structurally-modified poly(amide-imide)s.

Synthesis of aromatic poly(amide-imide)s from novel diimide-diacid (DIDA) containing sulphone and bulky pendant groups by direct polycondensation with various diamines

A novel diimide-diacid (DIDA) monomer, 4-{4-[(4-methyl phenyl) sulphonyl]}-1,3-bis-trimellitoimido benzene containing sulphone and bulky pendant groups was successfully synthesized and used to synthesize a series of wholly aromatic poly(amide-imide)s (PAIs) by direct polycondensation method. The direct polycondensation of newly synthesized DIDA with different diamines was carried out via Yamazaki’s phosphorylation method using triphenyl phosphite and pyridine system. The resulting poly(amide-imide)s were obtained in quantitative yields with inherent viscosities 0.36–0.47 dl/g in DMAc at 30 ± 0.1 °C. The poly(amide-imide)s were amorphous and were readily soluble in various solvents such as N-methyl-2-pyrrolidinone (NMP), N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), and pyridine. Tough and flexible films were obtained by casting their DMAc solution. According to thermogravimetric analysis, the polymers were fairly stable up to temperature around 396 °C, and 10% weight losses in the temperature range of 476–511 °C that showed good thermal stabilities of these polymers.

Synthesis and characterization of heterocyclic, and optically active poly(amide-imide)s by phosphorylation polycondensation

N,N′-Pyromelliticdiimido-di-L-methionine (1), N,N′-Pyromelliticdiimido-di-L-alanine (2), N,N′-Pyromelliticdiimido-di-L-phenylalanine (3) , and N,N′-Pyromelliticdiimido-di-L-leucine (4) were prepared from the reaction of Pyromellitic dianhydride with corresponding L-amino acids in a mixture of glacial acetic acid and pyridine solution (3/2 ratio) under refluxing conditions. The phosphorylation polycondensation of the corresponding diimide-diacid monomers with 4-phenyl-2,6-bis(4-aminophenyl) pyridine (6) or 4-(p-methylthiophenyl)-2,6-bis(4-aminophenyl) pyridine (8) were carried out in N-methyl-2-pyrolidone (NMP). The resulting poly (amide-imide)s were obtained in quantitative yields, showed admirable inherent viscosities (0.20-0.97 dl g-1), were soluble in polar aprotic solvents, showed good thermal stability and high optical purity. The synthetic compounds were characterized by IR, MS, 1H NMR and 13C NMR spectroscopy, elemental analysis and specific rotation.

Synthesis and characterization of new optically active and photolable poly (amide-imide)s from N,N ′-(3,3′,4,4′-benzophenonetetracarboxylic)-3,3′,4,4′-diimido-di-L-methionine and different diamines

N,N′-(3,3′,4,4′-benzophenonetetracarboxylic)-3,3′,4,4′-diimido-di-L-methionine (3) was prepared from the reaction of 3,3′,4,4′-benzophenonetetracarboxylic-3,3′,4,4′-dianhydride (1) with L-methionine (2) in a solution of (glacial acetic acid/pyridine) at refluxing temperature. The phosphorylation polycondensation of the diimide-diacid monomer (3) with 1,3-phenylenediamine (4a), 1,4-phenylenediamine (4b), 2,6-diaminopyridine (4c), 3,5-diaminopyridine (4d), 4,4′-diaminobiphenyl (4e) and 4,4′-diaminodiphenylsulfone (4f) was carried out in N-methyl-2-pyrolidone (NMP). The resulting poly (amide-imide)s showed admirable moderate inherent viscosities (0.23–0.48 dl g-1), good thermal stability and improved optical activity. All of the above compounds were fully characterized by IR spectroscopy, elemental analysis and specific rotation. Some structural characterization and physical properties of these new poly (amide-imide)s are presented.

Synthesis and properties of poly(amide–imide)s based on N,N′‐bis(4‐carboxyphenyl)‐4,4′‐oxydiphthalimide, p‐aminobenzoic acid and various aromatic diamines

AbstractA new diimide–diacid monomer, N,N′‐bis(4‐carboxyphenyl)‐4,4′‐oxydiphthalimide (I), was prepared by azeotropic condensation of 4,4′‐oxydiphthalic anhydride (ODPA) and p‐aminobenzoic acid (p‐ABA) at a 1:2 molar ratio in a polar solvent mixed with toluene. A series of poly(amide–imide)s (PAI, IIIa–m) was synthesized from the diimide–diacid I (or I′, diacid chloride of I) and various aromatic diamines by direct polycondensation (or low temperature polycondensation) using triphenyl phosphite and pyridine as condensing agents. It was found that only IIIk–m having a meta‐structure at two terminals of the diamine could afford good quality, creasable films by solution‐casting; other PAIs III using diamine with para‐linkage at terminals were insoluble and crystalline; though IIIg–i contained the soluble group of the diamine moieties, their solvent‐cast films were brittle. In order to improve their to solubility and film quality, copoly(amide–imide)s (Co‐PAIs) based on I and mixtures of p‐ABA and aromatic diamines were synthesized. When on equimolar of p‐ABA (m = 1) was mixed, most of Co‐PAIs IV had improved solubility and high inherent viscosities in the range 0.9–1.5 dl g−1; however, their films were still brittle. With m = 3, series V was obtained, and all members exhibited high toughness. The solubility, film‐forming ability, crystallinity, and thermal properties of the resultant poly(amide–imide)s were investigated.© 2002 Society of Chemical Industry