Synthesis and characterization of highly soluble poly(ether imide)s containing indane moieties in the main chain

A new indane containing unsymmetrical diamine monomer ( 3 ) was synthesized. This diamine monomer leads to a number of novel semifluorinated poly (ether imide)s when reacted with different commercially available dianhydrides like benzene‐1,2,4,5‐tetracarboxylic dianhydride (PMDA), benzophenone‐3,3′, 4,4′‐tetracarboxylic dianhydride (BTDA), 4,4′‐(hexafluoro‐isopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 4,4′‐(4,4′‐Isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) by thermal imidization route. All the poly(ether imide)s showed excellent solubility in several organic solvents such as N‐methylpyrrolidone (NMP), N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), tetrahydrofuran (THF), chloroform (CHCl₃) and dichloromethane (DCM) at room temperature. These light yellow poly (ether imide)s showed very low water absorption (0.19–0.30%) and very good optical transparency. Wide angle X‐ray diffraction measurements revealed that these polymers were amorphous in nature. The polymers exhibited high thermal stability up to 526°C in nitrogen with 5% weight loss, and high glass transition temperature up to 265°C. The polymers exhibited high tensile strength up to 85 MPa, modulus up to 2.5 GPa and elongation at break up to 38%, depending on the exact polymer structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Gas permeability and permselectivity of polyimides prepared from phenylenediamines with methyl substitution at the ortho position

Polyimides were prepared from diamines: 2,4,6-trimethyl-1,3-phenylenediamine (3MPDA) and 2,3,4,5-tetramethyl-1,4-phenylenediamine (4MPDA). 1,4-Bis(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), 3,3′-4,4′-diphenylsulphone tetracarboxylic dianhydride (SO₂PDA), 3,3′,4,4′-diphenylsulphide tetracarboxylic dianhydride (SPDA), pyromellitic dianhydride (PMDA), and 2,2′-bis(3,4-dicarboxyphenyl)hexafluoroisopropane dianhydride (6FDA) were used as dianhydride. The gas permeabilities of H₂, O₂ and N₂ through the polyimides were measured at temperatures from 30 °C to 90 °C. The results show that as methyl and trifluoromethyl substitution groups densities increase from 7.73 × 10⁻³ mol cm⁻³ to 13.50 × 10⁻³ mol cm⁻³, the peameability of H₂ increases 10-fold at 60% loss of permselectivity of H₂/N₂; however, the permeability of O₂ increases 20-fold at 20% loss of permselectivity of O₂/N₂. For O₂/N₂ separation, PMDA-3MPDA has similar performance to 6FDA-3MPDA and 6FDA-4MPDA; all have higher permeabilities for O₂ than normal polyimides, and the P(O₂)/α(O₂/N₂) trade-off relationships lie on the upper bound line for polymers. © 1999 Society of Chemical Industry     

Synthesis,characterization, and gas permeability of aromatic polyimides containing pendant phenoxy group

A diamine containing a pendant phenoxy group, 1-phenoxy-2,4-diaminobenzene, was synthesized and condensed with different aromatic dianhydrides [4,4′-oxydiphthalic dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracorboxylic dianhydride, and pyromellitic dianhydride] by one-step synthesis at a high temperature in m-cresol to obtain polyimides in high yields. Most of the polyimides exhibited good solvent solubility and could be readily dissolved in chloroform, sym-tetrachloroethane, N,N-dimethylformamide, N,N-dimethylacetamide, and nitrobenzene. Their inherent viscosities were in the range of 0.33–1.16 dL/g. Wide-angle X-ray spectra revealed that these polymers were amorphous in nature. All these polyimides were thermally stable, having initial decomposition temperatures above 500°C and glass-transition temperatures in the range of 248–281°C. The gas permeability of 4,4′-oxydiphthalic dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride based polyimides was investigated with pure gases: He, H₂, O₂, Ar, N₂, CH₄, and CO₂. A polyimide containing a  C(CF₃)₂ linkage showed a good combination of permeability and selectivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Resistive switching characteristics of polyimides derived from 2,2′‐aryl substituents tetracarboxylic dianhydrides

2,2′‐Position aryl‐substituted tetracarboxylic dianhydrides including 2,2′‐bis(biphenyl)‐4,4′,5,5′‐biphenyl tetracarboxylic dianhydride and 2,2′‐bis[4‐(naphthalen‐1‐yl)phenyl)]‐4,4′,5,5′‐biphenyl tetracarboxylic dianhydride were synthesized. A new series of aromatic polyimides (PIs) were synthesized via a two‐step procedure from 3,3′,4,4′‐biphenyl tetracarboxylic dianhydride and the newly synthesized tetracarboxylic dianhydrides monomers reacting with 2,2′‐bis[4′‐(3″,4″,5″‐trifluorophenyl)phenyl]‐4,4′‐biphenyl diamine. The resulting polymers exhibited excellent organosolubility and thermal properties associated with T_g at 264 °C and high initial thermal decomposition temperatures (T_5%) exceeding 500 °C in argon. Moreover, the fabricated sandwich structured memory devices of Al/PI‐a/ITO was determined to present a flash‐type memory behaviour, while Al/PI‐b/ITO and Al/PI‐c/ITO exhibited write‐once read‐many‐times memory capability with different threshold voltages. In addition, Al/polymer/ITO devices showed high stability under a constant stress or continuous read pulse voltage of ? 1.0 V. Copyright © 2011 Society of Chemical Industry     

Synthesis and properties of polyimides derived from diamine monomer containing bi-benzimidazole unit

A new aromatic heterocyclic diamine monomer containing bi-benzimidazole unit, 2,2-bis(4′-aminophenyl)-5,5-bi-1H-benzimidazole, was synthesized from 2,2-bis(4′-nitrophenyl)-5,5-bi-1H-benzimidazole (BNPBBI) prepared via the reaction of 3,3′,4,4′-biphenyltetramine and p-nitrobenzaldehyde with a high yield. Their compositions and chemical structures containing polybenzimidazole backbone were characterized by FTIR, ¹H NMR and elemental analysis. A series of aromatic polyimides containing the heterocyclic moiety in the main chain were prepared by the reaction of BAPBBI with various aromatic dianhydrides of 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride or pyromellitic dianhydride. The polymers possess a high glass transition temperature of >415 °C and a good thermal stability up to 566 °C with a 5 % weight loss. The combination of polybenzimidazole and polyimide via introducing BAPBBI into the main chains provides the rigid structure, and macromolecular interactions are thus enhanced, resulting in the outstanding mechanical properties. These polyimides exhibit the strong tensile strength of 201 to 327 MPa, and the ultrahigh tensile moduli of 10.7 to 15.5 GPa without post stretching.     

Tris(3-aminophenyl)Phosphine oxide-based nadimide resins. II

A series of phosphorus-containing nadimide end-capped resins having different backbones was prepared by reacting endo-5-norbornene-2-3-dicarboxylic acid anhydride (nadic anhydride), pyromellitic dianhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6F) and tris(3-aminophenyl)phosphine oxide (TAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, FTIR, and ¹H-NMR. Thermogravimetric studies revealed a multistep decomposition reaction for uncured resins. Residual weight at 800°C in nitrogen was found to be 50–60%. Resins cured at 300°C for 1 h in air atmosphere were stable up to 440 ± 20°C and decomposed in a single step above this temperature. The char yields of cured resins were in the range 63–71.5%. © 1992 John Wiley & Sons, Inc.     

Synthesis and characterization of some aromatic polyimides

The diamine 2‐methyl‐1,3‐bis(4‐aminophenyloxy)benzene was prepared via a nucleophilic substitution reaction and was characterized with Fourier transform infrared, elemental analysis, and ¹H‐ and ¹³C‐NMR spectroscopy. The prepared diamine was also characterized with single‐crystal analysis. The geometric parameters of C₁₉H₁₈N₂O₂ were in the usual ranges. The dihedral angles between the central phenyl ring and the two terminal aromatic rings were 88.9 and 91.6°. The crystal structure was stabilized by N? H···N hydrogen bonds. The diamine was then polymerized with 3,3′,4,4′‐benzophenone tetracarboxylic acid dianhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, 3,4,9,10‐perylenetetracarboxylic acid dianhydride, and pyromellitic dianhydride by either a one‐step solution polymerization reaction or a two‐step procedure. These polymers had inherent viscosities ranging from 0.61 to 0.85 dL/gm. Some of the polymers were soluble in most common organic solvents even at room temperature, and some were soluble on heating. The degradation temperatures of the resultant polymers fell in the range of 260–500°C in nitrogen (with only 10% weight loss). The specific heat capacity at 200°C ranged from 1.0 to 2.21 J g^?1 K^?1. The temperatures at which the maximum degradation of the polymer occurred ranged from 510 to 610°C. The glass‐transition temperatures of the polyimides ranged from 182 to 191°C. The activation energy and enthalpy of the polyimides ranged from 44.44 to 73.91 kJ/mol and from 42.58 to 72.08 kJ/mol K, respectively. The moisture absorption was found in the range of 0.23–0.71%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,characterization, thermal and optical properties of soluble polyimides derived from an unsymmetrical diamine

A new unsymmetrical diamine monomer, 2,4‐diaminophenyl [4′‐(2′′,6′′‐diphenyl‐4′′‐pyridyl)phenyl]ether, was successfully synthesized by nucleophilic substitution of 1‐chloro‐2,4‐dinitrobenzene with 4‐(2′,6′‐diphenyl‐4′‐pyridyl) phenol. The diamine monomer was characterized by FTIR, ¹H and ¹³C NMR, and elemental analysis techniques and used for the preparation of novel polyimides (PIs) by reaction with commercially available tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and bicyclo[2.2.2]‐oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride. These PIs with inherent viscosities ranged from 0.43 to 0.48 dL/g were readily soluble in many organic solvents and afforded tough and flexible films by solution casting. These polymers exhibited T_gs between 237 and 294°C, and 10% weight loss temperatures in excess of 500°C with up to 56% char yield at 600°C in air. Their maximum fluorescence emission in dilute (0.2 g/dL) NMP solution appeared at 450 nm. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of aromatic polyimide,poly(benzoxazole imide), and poly(benzoxazole amide imide)

Two series of heterocyclic aromatic polymers were synthesized from 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthaltic anhydride) and 2,2′‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride by two‐step method. The inherent viscosities were in the range of 24–45 cm³/g. The effects of the rigid benzoxazole group in the backbone of copolymer on the thermal, mechanical, and physical properties were investigated. These polymers exhibit good thermal stability. The temperatures of 5% weight loss (T₅) of these polymers are in the range of 403–530°C in air and 425–539°C in nitrogen. The chard yields of these polymers are in the range of 15–24% in air and 54–61% in nitrogen. These polymers also have high glass‐transition temperatures and a low coefficient of thermal expansion and good mechanical properties. The poly(benzoxazol imide) has a higher tensile strength and modulus than those of neat polyimide. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Methyl nadimide resins: Synthesis and characterization

This article describes the synthesis and characterization of several methyl nadimides endcapped resins based on tris(3-aminophenyl)phosphine oxide. These resins were prepared by reacting methyl-5-norbornene 2,3-dicarboxylic anhydride (methyl nadic anhydride) (MNA), pyromellitic dianhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6F), and tris(3-aminophenyl)phosphine oxide (TAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, IR, and ¹H-NMR. Thermal characterization of uncured resins using DSC and TGA techniques revealed an exothermic transition accompanied by a weight loss in the temperature range of 200–350°C. Residual weight at 800°C in nitrogen was found to be 47–55%. Isothermal curing of the resins was done at 340°C for 1 h in an air atmosphere. The cured resins were stable up to 400 ± 20°C. © 1994 John Wiley & Sons, Inc.     

Bis(3-aminophenyl)methyl phosphine oxide-based (methyl) nadicimide resins

Ten nadicimide/methyl nadicimide end-capped oligomeric resins were prepared by reacting endo-5-norbornene-2,3-dicarboxylic acid anhydride (methyl nadic anhydride), pyromellitic dianhydride (PMDA)/3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6F), and bis(3-aminophenyl) methyl phospine oxide (BAP) in glacial acetic acid/acetone. Structural characterization of the resins was done by elemental analysis, IR, and ¹H-NMR. Multistep decomposition was observed in the TG scan of uncured resins in a nitrogen atmosphere. Residual weight at 800°C depended on the structure and ranged between 25 and 51%. Isothermal curing of the resins was done at 300°C for 1 h in an air atmosphere. These cured resins were stable to 350 ± 30°C and decomposed in a single step above this temperature. The char yield of the resins increased on curing and was in the range 34–70%. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:861–869, 1997     

Synthesis of highly soluble and transparent polyimides

A novel aromatic diamine, 3,3′‐diisopropyl‐4,4′‐diaminophenyl‐4″‐methyltoluene with a 4‐methylphenyl pendant group and isopropyl side groups, was designed and synthesized in this study. Then it was polymerized with various aromatic dianhydrides including pyromellitic dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride, 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride via a one‐pot high temperature polycondensation procedure to produce a series of aromatic polyimides. These polyimides exhibited excellent solubility even in common organic solvents, such as chloroform and tetrahydrofuran. The flexible and tough films can be conveniently obtained by solution casting. The films were nearly colorless and exhibited high optical transparency, with the UV cutoff wavelength in the range 302–365 nm and the wavelength of 80% transparency in the range 385–461 nm. Moreover, they showed low dielectric constants (2.73–3.23 at 1 MHz) and low moisture absorption (0.13%–0.46%). Furthermore, they also possessed good thermal and thermo‐oxidative stability with 10% weight loss temperatures (T_10%) in the range 489–507 °C in a nitrogen atmosphere. The glass transition temperatures of all polyimides are in the range 262–308 °C. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of polyimides and co-polyimides having pendant benzoic acid moiety

A novel diamine monomer, 2,4-diamino-4′-carboxy diphenyl ether had been synthesized. Several polyimides were prepared by reacting this diamine with commercially available dianhydrides, such as benzophenone tetracarboxylic acid dianhydride (BTDA), 4,4′-bis{hexafluoroisopropylidene bis (phthalic anhydride)}(6-FDA), oxydiphthalic anhydride (ODPA) and 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA). Furthermore, copolymers from the resulting diamine and oxydianiline (ODA) with 6 FDA were also synthesized. The inherent viscosities of the polymers were 0.42-0.67 dl g⁻¹. The polymers have good solubility in polar aprotic solvents, high thermal stability up to 410 °C in nitrogen and high glass transition temperatures (T_g) ranging from 260-330 °C. These polymers formed tough flexible films by solution casting.     

Thermally stable polyureas and poly(urea‐imide)s containing zinc and nickel napthtrien complexes

Two new napthtrien metal complexes, MNapth₂trien; where M = Zn and Ni, were synthesized and used for the synthesis of metal‐containing polyureas and poly(urea‐imide)s. MNapth₂trien underwent polymerization reaction with two diisocyanates, namely, 4,4′‐diphenylmethane diisocyanate and isophorone diisocyanate to yield polyureas. Poly(urea‐imide)s were obtained by the synthesis of metal‐containing isocyanate‐terminated polyurea prepolymers from the reaction between MNapth₂trien and excess diisocyanates, which could then undergo further reaction with different dianhydrides. The dianhydrides used were pyromellitic dianhydride and benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride. The polymers were characterized by infrared, nuclear magnetic resonance, elemental analysis, X‐ray diffraction, solubility, and viscosity. Glass transition temperature of the polymers was obtained from differential scanning calorimetry and dynamic mechanical thermal analysis. Thermal stability of polymers was studied by thermogravimetric analysis in air. It was found that the resulting metal‐containing polymers exhibited good thermal stability. Initial decomposition temperatures of the polymers depend on the amount of MNapth₂trien in the polymer composition. Char yields of metal‐containing poly(urea‐imide)s are higher than those of metal‐containing polyureas. Most metal‐containing polymers show good solubility in organic solvents. Shore D hardness test indicates that metal‐containing poly(urea‐imide)s are hard materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of soluble and thermally stable polyimides from 3,5‐diamino‐N‐(4‐(8‐quinolinoxy) phenyl) aniline and various dianhydrides

Three novel polyimides (PIs) having pendent 4‐(quinolin‐8‐yloxy) aniline group were prepared by polycondensation of a new diamine with commercially available tetracarboxylic dianhydrides, such as pyromellitic dianhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and bicyclo[2.2.2]‐oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride. These PIs were characterized by FTIR, ¹H NMR, and elemental analysis; they had high yields with inherent viscosities in the range of 0.4–0.5 dl g⁻¹, and exhibited excellent solubility in many organic solvents such as N,N‐dimethyl acetamide, N,N′‐dimethyl formamide, N‐methyl pyrrolidone (NMP), dimethyl sulfoxide, and pyridine. These PIs exhibited glass transition temperatures (T_g) between 250 and 325° C. Their initial decomposition temperatures (T_i) ranged between 270 and 450°C, and 10% weight loss temperature (T₁₀) up to 500°C with 68% char yield at 600°C under nitrogen atmosphere. Transparent and hard polymer films were obtained via casting from their NMP solutions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of organo‐soluble polyimides based on 4,4′‐diamino‐3,3‐dimethyldiphenylmethane and conventional dianhydrides

4,4′‐Diamino‐3,3′‐dimethyldiphenylmethane was used to prepare polyimides in an attempt to achieve good organo‐solubility and light color. Polyimides based on this diamine and three conventional aromatic dianhydrides were prepared by solution polycondensation followed by chemical imidization. They possess good solubility in aprotonic polar organic solvents such as N‐methyl 2‐pyrrolidone, N,N‐dimethyl acetamide, and m‐cresol. Polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is even soluble in common solvents such as tetrahydrofuran and chloroform. Polyimides exhibit high transmittance at wavelengths above 400 nm. The glass transition temperature of polyimide from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and pyromellitic dianhydride is 370°C, while that from 4,4′‐diamino‐3,3′‐dimethyldiphenylmethane and diphenylether‐3,3′,4,4′‐tetracarboxylic acid dianhydride is about 260°C. The initial thermal decomposition temperatures of these polyimides are 520–540°C. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1299–1304, 1999     

Synthesis and properties of thermostable naphthalate-containing copoly(amide–imide)s

Thermostable naphthalate-containing copoly(amide-imide)s with inherent viscosity of 0.53–0.96 dL/g were synthesized by reacting diacid-terminated naphthalate monomers with various diisocyanate-terminated polyimide prepolymers. The poly-imide prepolymers were prepared by using 4,4′-diphenylmethane diisocyanate to react with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, or 3,3′,4,4′-sulfonyl diphthalic anhydride using a direct one-pot method to improve their solubility without sacrificing their thermal properties. The copolymers, except the B-2 and P-2 series, can be dissolved in N,N-dimethylacetamide and 5% lithium chloride or dimethyl sulfoxide at high temperature but are not soluble in pyridine. The solubility of the copolymers is related to their chemical and crystalline structures. Those copolymers with sulfonyl or amorphous structures display good solubility. All the naphthalate-containing copoly(amide-imide)s have glass transition temperatures and melting points in the range of 223–312°C and 348–366°C, respectively, and show a 10% weight-loss temperature of 485–549°C in air and 465–564°C in a nitrogen atmosphere. The tensile strength, elongation at break, and initial modulus of polymer films range from 25–74 MPa, 4–9%, and 0.74–1.60 GPa, respectively. From the X-ray diffraction studies, copolymers of B-2, P-2, and D-2 with symmetrical 2,6-naphthalate amide structure are crystalline, but the others are amorphous. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1581–1593, 1997     

Synthesis and characterization of polyimides and polyamide-imides containing azomethine linkages

Polyimides and polyamide-imides containing azomethine linkages in the polymer backbone have been synthesized from 4,4′-bis(4-isocyanatobenzylidene)-diaminodiphenylether (ODAI), 4,4′-bis(4-isocyanatobenzylidene)-diaminodiphenyl-methane (MADI), 4,4′-bis(4-isocyanatobenzylidene)-diaminodiphenylsulphone (SDAI), pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA), and trimellitic anhydride (TMA), by a one-step process. The diisocyanates ODAI, MDAI and SDAI were prepared from the corresponding diacids, namely, 4,4′-bis(4-carboxybenzylidene)-diaminodiphenylether (ODAA), 4,4′-bis(4-carboxybenzylidene)-diaminodiphenylmethane (MDAA) and 4,4′-bis-(4-carboxybenzylidene)-diaminodiphenylsulphone (SDAA) by a Weinstock-modified Curtius rearrangement method. All the polycondensation reactions were conducted in N-methyl-2-pyrrolidone (NMP) under identical conditions and the polymers obtained were characterized by IR spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction.     

Preparation of poly(amic acid) and polyimide derived from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride with different diamines by microwave irradiation

Polycondensation‐type poly(amic acid) (PAA) was synthesized with 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride as a dianhydride monomer and 4,4′‐diaminodiphenylmethane and 4,4′‐oxydianiline as diamine monomers under microwave irradiation in dimethylformamide. Then, PAA was used to make polyimide (PI) by imidization at a low temperature. The structure and performance of the polymers were characterized with Fourier transform infrared (FTIR), proton nuclear magnetic resonance (¹H‐NMR), viscosity, X‐ray diffraction (XRD), and thermogravimetry (TG) curve analyses. The FTIR spectra of the polymers showed characteristic peaks of PI around 1779 and 1717 cm^?1. The ¹H‐NMR spectrum of PAA indicated a singlet at 6.55 ppm assigned to ? NHCO? and a singlet at 10.27 ppm assigned to carboxylic acid protons. The XRD spectrum demonstrated that the obtained PI had a low‐order aggregation structure with a d‐spacing of 0.5453 nm. The TG results revealed that the PI was thermally stable with 10% weight loss at 565°C in an N₂ atmosphere. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Synthesis and thermal,mechanical and gas permeation properties of aromatic polyimides containing different linkage groups

Two series of aromatic polyimides containing various linkage groups based on 2,7‐bis(4‐aminophenoxy)naphthalene or 3,3′‐dimethyl‐4,4′‐diaminodiphenylmethane and different aromatic dianhydrides, namely 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride), 4,4′‐(hexafluoroisopropylidene)bis(phthalic anhydride), 3,3′,4,4′ benzophenonetetracarboxylic dianhydride, 9,9‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]fluorene dianhydride and 4,4′‐(4,4′‐hexafluoroisopropylidenediphenoxy)bis(phthalic anhydride), were synthesized and compared with regard to their thermal, mechanical and gas permeation properties. All these polymers showed high thermal stability with initial decomposition temperature in the range 475–525 °C and glass transition temperature between 208 and 286 °C. Also, the polymer films presented good mechanical characteristics with tensile strength in the range 60–91 MPa and storage modulus in the range 1700–2375 MPa. The macromolecular chain packing induced by dianhydride and diamine segments was investigated by examining gas permeation through the polymer films. The relationships between chain mobility and interchain distance and the obtained values for gas permeability are discussed. © 2014 Society of Chemical Industry