Synthesis and properties of polyimides derived from 1,6-bis(4-aminophenoxy)naphthalene and aromatic tetracarboxylic dianhydrides

1,6-Bis(4-aminophenoxy)naphthalene ( I ) was used as a monomer with various aromatic tetracarboxylic dianhydrides to synthesize polyimides via a conventional two-stage procedure that included ring-opening polyaddition in a polar solvent such as N,N-dimethylacetamide (DMAc) to give poly(amic acid)s, followed by thermal cyclodehydration to polyimides. The diamine ( I ) was prepared through the nucleophilic displacement of 1,6-dihydroxynaphthal-ene with p-chloronitrobenzene in the presence of K₂CO₃, followed by catalytic reduction. Depending on the dianhydrides used, the poly(amic acid)s obtained had inherent viscosities of 0.73–2.31 dL/g. All the poly(amic acid)s could be solution cast and thermally converted into transparent, flexible, and tough polyimide films. The polyimide films had a tensile modulus range of 1.53–1.84 GPa, a tensile strength range of 95–126 MPa, and an elongation range at break of 9–16%. The polyimide derived from 4,4′-sulfonyldiphthalic anhydride (SDPA) had a better solubility than the other polyimides. These polyimides had glass transition temperatures between 248–286°C (DSC). Thermogravimetric analyses established that these polymers were fairly stable up to 500°C, and the 10% weight loss temperatures were recorded in the range of 549–595°C in nitrogen and 539–590°C in air atmosphere. © 1995 John Wiley & Sons, Inc.     

Synthesis and properties of polyimides derived from 1,4-bis(4-aminophenoxy)2,5-di-tert-butylbenzene

Novel aromatic polyimides containing symmetric, bulky di-tert-butyl substituents unit were synthesized from 1,4-bis(4-aminophenoxy)2,5-di-tert-butylbenzene (BADTB) and various aromatic tetracarboxylic dianhydrides by the conventional two-stage procedure that included ring-opening polyaddition in a polar solvent such as N,N-dimethylacetamide to give poly(amic acid)s, followed by cyclodehydration to polyimides. The diamine was prepared through the nucleophilic displacement of 2,5-di-tert-butylhydroquinone with p-chloronitrobenzene in the presence of K₂CO₃, followed by catalytic reduction. Depending on the dianhydrides used, the poly(amic acid)s obtained had inherent viscosities of 0.83–1.88 dL g⁻¹. Most of the polyimides formed transparent, flexible, and tough films. Tensile strength and elongation at break of the BADTB-based polyimide films ranged from 68–93 MPa and 7–11%, respectively. The polyimide derived from 4,4′-hexafluoro-isopropylidenebisphathalic anhydride had better solubility than the other polyimides. These polyimides had glass transition temperatures between 242–298°C and 10% mass loss temperatures were recorded in the range of 481–520°C in nitrogen. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1527–1534, 1997     

Synthesis and properties of polyimides derived from 1,7-bis(4-aminophenoxy)naphthalene and aromatic tetracarboxylic dianhydrides

The novel diamine, 1,7-bis(4-aminophenoxy)naphthalene (1,7-BAPON), was synthesized and used to prepared polyimides. 1,7-BAPON was synthesized through the nucleophilic displacement of 1,7-dihydroxynaphthalene with p-fluoronitrobenzene in the presence of K₂CO₃ followed by catalytic-reduction. Polyimides were prepared from 1,7-BAPON and various aromatic tetracarboxylic dianhydrides by the usual two-step procedure that included ring-opening polyaddition to give poly(amic acid)s, followed by cyclodehydration to polyimides. The poly(amic acid)s had inherent viscosities of 0.74-2.48 dL/g. Most of the polyimides formed tough, creasible films. These polyimides had glass transition temperatures between 247–278°C and their 10% weight loss temperatures were recorded in the range of 515–575°C in nitrogen atmosphere. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of new cardo polyimides prepared from 5,5-Bis[4-(4-aminophenoxy)phenyl]-4,7-methanohexahydroindane

A new cardo diamine monomer, 5,5-bis[4-(4-aminophenoxy)phenyl]-4,7-methanohexahydroindane (II), was prepared in two steps with high yield. The monomer was reacted with six different aromatic tetracarboxylic dianhydrides in N,N-dimethylacetamide (DMAc) to obtain the corresponding cardo polyimides via the poly(amic acid) precursors and thermal or chemical imidization. All the poly(amic acid)s could be cast from their DMAc solutions and thermally converted into transparent, flexible, and tough polyimide films which were further characterized by x-ray and mechanical analysis. All of the polymers were amorphous and the polyimide films had a tensile strength range of 89–123 MPa, an elongation at break range of 6–10%, and a tensile modulus range of 1.9–2.5 GPa. Polymers V_c, V_e, and V_f exhibited good solubility in a variety of solvents such as N-methyl-2-pyrrolidinone (NMP), DMAc, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, γ-butyrolactone, and even in tetrahydrofuran and chloroform. These polyimides showed glass-transition temperatures between 274 and 299°C and decomposition temperatures at 10% mass loss temperatures ranging from 490 to 521°C and 499 to 532°C in nitrogen and air atmospheres, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2815–2821, 1999     

Syntheses and properties of aromatic polyamides and polyimides derived from 9,9-bis[4-(p-aminophenoxy)phenyl]fluorene

9,9-Bis[4-(p-aminophenoxy)phenyl]fluorene ( II ) was used as a monomer with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to synthesize polyamides and polyimides, respectively. The diamine II was derived by a nucleophilic substitution of 9,9-bis(4-hydroxyphenyl)fluorene with p-chloronitrobenzene in the presence of K₂CO₃ and then hydro-reduced. Polyamides IV _a-g having inherent viscosities of 0.73–1.39 dL/g were prepared by the direct polycondensation of the diamine II with various aromatic diacids using triphenyl phosphite and pyridine as condensing agents. All the aromatic polyamides were amorphous and readily soluble in various polar solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, and N-methyl-2-pyrrolidone. Transparent and flexible films of these polymers could be cast from the DMAc solutions. These aromatic polyamides had glass transition temperatures in the range of 283–309°C and 10% weight loss occurred up to 460°C. The polyimides were synthesized from diamine II and various aromatic dianhydrides via the two-stage procedure that included ring-opening poly-addition in DMAc to give poly(amic acid)s, followed by thermal or chemical conversion to polyimides. The poly(amic acid)s had inherent viscosities of 0.62–1.78 dL/g, depending on the dianhydrides. Most of the aromatic polyimides obtained by chemical cyclization were found to be soluble in NMP. These polyimides showed almost no weight loss up to 500°C in air or nitrogen atmosphere. © 1993 John Wiley & Sons, Inc.     

Syntheses and properties of aromatic polyamides and polyimides based on N-phenyl-3,3-bis[4-(p-aminophenoxy) phenyl] phthalimidine

N-Phenyl-3,3-Bis[4-(p-aminophenoxy)phenyl] phthalimidine ( II ) was used as a monomer with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to synthesize polyamides and polyimides, respectively. The diamine II was derived by a nucleophilic substitution of N-phenyl-3,3-bis(4-hydroxyphenyl) phthalimidine with p-chloronitrobenzene in the presence of K₂CO₃ and then hydro-reduced. Polyamides IV _a-g having inherent viscosities of 0.55–1.64 dL/g were prepared by the direct polycondensation of the diamine II with various aromatic diacids using triphenyl phosphite and pyridine as condensing agents. All the aromatic polyamides were amorphous and readily soluble in various polar solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, dimethylsulfoxide, and N-methyl-2-pyrrolidone (NMP). Transparent and flexible films of these polymers could be cast from the DMAc solutions. These aromatic polyamides had glass transition temperatures in the range of 293–319°C and 10% weight loss occurred up to 480°C. The polyimides were synthesized from diamine II and various aromatic dianhydrides via the two-stage procedure that included ring-opening polyaddition in DMAc to give poly(amic acid)s, followed by thermal or chemical conversion to polyimides. Most of the aromatic polyimides obtained by chemical cyclization were found to be soluble in NMP, m-cresol, and o-chlorophenol. These polyimides showed almost no weight loss up to 500°C in air or nitrogen atmosphere. © 1994 John Wiley & Sons, Inc.     

Highly soluble fluorinated polyimides based on an asymmetric bis(ether amine): 1,7‐bis(4‐amino‐2‐trifluoromethylphenoxy)naphthalene

A novel structurally asymmetric bis(ether amine) monomer containing trifluoromethyl groups, 1,7‐bis(4‐amino‐2‐trifluoromethylphenoxy)naphthalene, was prepared through the nucleophilic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride and 1,7‐dihydroxynaphthalene in the presence of potassium carbonate in N‐methyl‐2‐pyrrolidone (NMP), followed by catalytic reduction with hydrazine and Pd/C in ethanol. A series of new fluorine‐containing polyimides were synthesized from the diamine with various commercially available aromatic tetracarboxylic dianhydrides using a two‐stage process with thermal or chemical imidization method. The intermediate poly(amic acid)s had inherent viscosities between 0.93 and 1.93 dL/g. Most of the polyimides obtained from both routes were readily soluble in many organic solvents such as NMP and N,N‐dimethylacetamide (DMAc). All the polyimides could afford transparent, flexible, and strong films with low moisture absorptions of 0.29–0.69%, low dielectric constants of 2.81–3.23 at 10 kHz, and an ultraviolet‐visible absorption cutoff wavelength at 358–423 nm. The glass‐transition temperatures (T_gs) (by DSC) and softening temperatures (by thermomechanical analysis) of the polyimides were recorded in the range of 222–271 °C and 210–266 °C, respectively. Decomposition temperatures for 10% weight loss all occurred above 500 °C in both nitrogen and air atmospheres. For a comparative study, some properties of the present polyimides will be compared with those of structurally related ones derived from 1,7‐bis(4‐aminophenoxy)naphthalene and 1,5‐bis(4‐amino‐2‐trifluoromethylphenoxy)naphthalene. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1756–1770, 2009     

Polyimides with alicyclic diamines. I. Syntheses and thermal properties

The polyaddition reactions of alicyclic diamines such as 1,4-diaminocyclohexane (1,4-CHDA) or 4,4′-diaminodicyclohexylmethane (DCHM) and configurational isomers of 1,4-CHDA or DCHM with tetracarboxylic aromatic anhydrides in aprotic solvents were carried out to prepare high molecular weight poly(amic acid)s. Through the thermal imidization of poly(amic acid)s, several flexible polyimide films were prepared. Because of the stiffness of the alicyclic moieties in diamines, the resulting polyimides exhibit high glass transition temperatures (220–340°C) almost similar to those for corresponding aromatic polyimides which have phenylene groups in place of cyclohexyl groups, and show good thermal stability. The partial crystallization was observed for polyimides with trans-cyclohexyl moiety during the heating in differential scanning calorimetry and ascertained by wide-angle x-ray diffraction. Thus, the inhibition of the occurrence of charge transfer in polyimides is accomplished by introducing alicyclic diamines in place of aromatic diamines without reducing their thermal stability. © 1993 John Wiley & Sons, Inc.     

Synthesis and properties of new hydroxyl‐pendant aromatic polyimides derived from trimethylsilylated 4,4′‐diamino‐3,3′‐dihydroxybiphenyl and aromatic tetracarboxylic dianhydrides

New phenolic hydroxyl‐pendant aromatic polyimides were synthesized with the N‐silylated diamine method in two steps: the ring‐opening polyaddition of tetrakis(trimethylsilyl)‐substituted 4,4′‐diamino‐3,3′‐dihydroxybiphenyl to various aromatic tetracarboxylic dianhydrides, giving trimethylsiloxy‐pendant poly(amic acid) trimethylsilyl esters, and thermal imidization. The hydroxyl‐bearing polyimides were amorphous but insoluble in organic solvents. They had glass‐transition temperatures greater than 370 °C and temperatures of 10% weight loss greater than 415 °C in nitrogen. The hydroxyl‐pendant polypyromellitimide film had a high tensile strength and a high modulus of 310 MPa and 10 GPa, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1790–1795, 2002     

Preparation and properties of new polyimides derived from 1,6-diaminodiamantane

New polyimides containing diamantane units were prepared by a conventional two-step method starting from 1,6-diaminodiamantane and aromatic dianhydrides. The intermediate poly(amic acid)s had inherent viscosities of 0.33–0.55 dL/g. These polyimides did not decompose below 400°C in air or nitrogen atmosphere, and the temperature at 5% weight loss were above 491°C. The glass transition temperatures of the polyimides were found to be 375–429°C by DSC. These polyimides had almost the same semicrystalline patterns and exhibited crystalline diffraction peak (2 θ) at around 15°. The polyimide Vb exhibited a melting endothermic peak at 514°C. © 1996 John Wiley & Sons, Inc.     

Preparation and properties of aromatic polyimides from 2,2′-bis(p-aminophenoxy)biphenyl or 2,2′-bis)p-aminophenoxy)-1,1′-binaphthyl and aromatic tetracarboxylic dianhydrides

New aromatic polyimides containing a biphenyl-2,2′-diyl or 1,1′-binaphthyl-2,2′-diyl unit were prepared by a conventional two-step method starting from 2,2′-bis(p-aminophenoxy) biphenyl or 2,2′-bis(p-aminophenoxy)-1,1′-binaphthyl and aromatic tetracarboxylic dianhydrides. The polyimides having inherent viscosities of 0.69–0.99 and 0.51–0.59 dL/g, respectively, were obtained. Some of these polymers were readily soluble in a variety of organic solvents including N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide, and pyridine. Transparent, flexible, and pale yellow to brown films of these polymers could be cast from the DMAc or NMP polyamic acid solutions. These aromatic polyimides containing biphenyl and binaphthyl units had glass transition temperatures in the range of 200–235 and 286–358°C, respectively. They began to lose weight around 380°C, with 10% weight loss being recorded at about 470°C in air. © 1993 John Wiley & Sons, Inc.     

Preparation and properties of novel soluble aromatic polyimides from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides

New aromatic polyimides containing triphenylamine unit were prepared by two different methods, i.e., a conventional two-step method starting from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides and the one-step thioanhydride method starting from the aromatic diamine and aromatic tetracarboxylic dithioanhydrides. Both procedures yielded high-molecular-weight polyimides with inherent viscosities of 0.47–1.17 dL/g. Some of these polymers were soluble in organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, m-cresol, and pyridine. All the polyimides afforded transparent, flexible, and tough films, and the color varied from pale yellow to dark red, depending markedly on the tetracarboxylic acid components. The glass transition temperatures (T_gs) of these polyimides were in the range of 287–331°C and the 10% weight loss temperatures were above 520°C in air. The polyimides prepared by the one-step method exhibited better solubility in organic solvents and had somewhat lower T_gs than the polymers prepared by a conventional two-step method.     

Novel Non‐Coplanar and Tertbutyl‐Substituted Polyimides: Solubility,Optical, Thermal and Dielectric Properties

A novel aromatic diamine monomer bearing tertbutyl and 4‐tertbutylphenyl groups, 3,3′‐ditertbutyl‐4,4′‐diaminodiphenyl‐4′′‐tertbutylphenylmethane (TADBP), was prepared and characterized. A series of non‐coplanar polyimides (PIs) were synthesized via a conventional one‐step polycondensation from TADBP and various aromatic dianhydrides including pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (OPDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) and 4,4′‐(hexafluoroisopropylidene)dipthalic anhydride (6FDA). All PIs exhibit excellent solubility in common organic solvents such as N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), dimethyl sulfoxide (DMSO), chloroform (CHCl₃), tetrahydrofuran (THF), and so on. Furthermore, the obtained transparent, strong and flexible polyimide films present good thermal stability and outstanding optical properties. Their glass transition temperatures (T_gs) are in the range of 298 to 347°C, and 10% weight loss temperatures are in excess of 490°C with more than 53% char yield at 800°C in nitrogen. All the polyimides can be cast into transparent and flexible films with tensile strength of 80.5–101 MPa, elongation at break of 8.4%–10.5%, and Young's modulus of 2.3–2.8 GPa. Meanwhile, the PIs show the cutoff wavelengths of 302–356 nm, as well as low moisture absorption (0.30% –0.55%) and low dielectric constant (2.78–3.12 at 1 MHz).     

New polyimides incorporated with diphenylpyrenylamine unit as fluorophore and redox‐chromophore

A series of novel polyimides based on N,N‐di(4‐aminophenyl)‐1‐aminopyrene and aromatic or alicyclic tetracarboxylic dianhydrides were synthesized. The polymers exhibited good solubility in many polar organic solvents and could afford robust films via solution casting. The polyimides derived from aromatic dianhydrides exhibited high thermal stability and high glass‐transition temperatures (333–364 °C). Cyclic voltammetry studies of the polymer films showed that these polyimides are both p and n dopable and have multicolored electrochromic states. For the polyimides derived from alicyclic dianhydrides, they revealed a strong blue‐light emission with high fluorescence quantum yields (?_PL > 45%) and a marked solvatochromic behavior. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of new soluble aromatic polyimides from 3,4-bis (4-aminophenyl)-2,5-diphenylfuran and aromatic tetracarboxylic dianhydrides

New soluble polyimides with inherent viscosities of 0.2–0.6 dL/g were synthesized from 3,4-bis (4-aminophenyl)-2,5-diphenylfuran and various aromatic tetracarboxylic dianhydrides by the conventional two-step method which involved ring-opening polyaddition and subsequent cyclodehydration. Almost all of the polymides were generally soluble in a wide range of organic solvents such as N,N-dimethylacetamide, 1,3-dimethyl-2-imidazolidone, m-cresol, o-chlorophenol, and pyridine. The polyimide prepared from pyromellitic dianhydride was crystalline, whereas the other polyimides were amorphous. All the polyimides have glass transition temperatures in the range of 281–344°C and showed no appreciable weight loss up to 410°C in both air and nitrogen atmospheres.     

Phthalonitrile‐containing aromatic polyimide thin films with nano‐actuation properties

Polymer films of some polyimides containing pendant phthalonitrile groups were prepared by casting the corresponding poly(amic acid) solutions onto glass plates, followed by thermal imidization under controlled temperature conditions. The poly(amic acid)s were synthesized by polycondensation reaction of 4,4′‐diamino‐4″‐(3,4‐dicyanophenoxy)triphenylmethane, 1, or of different amounts of 1 and 4,4′‐bis(4‐aminophenoxybiphenyl), with two aromatic dianhydrides, 4,4′‐oxydiphthalic anhydride or benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride. Most of the films were flexible and tough and exhibited high thermal stability, having the initial decomposition temperature above 400 °C. Dynamic mechanical analysis and dielectric spectroscopy revealed the influence of phthalonitrile group content on the relaxation processes of polyimides. The values of the dielectric constant at 10 kHz and 20 °C were in the range of 3.25–3.61. The films exhibited nano‐actuation in the range of 240–480 nm, depending on the phthalonitrile group content, when an electric voltage was applied on their surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Polyimides derived from novel asymmetric ether diamine

A new aromatic asymmetrical ether diamine, 5‐(4‐aminophenoxy)‐1‐naphthylamine, was synthesized through the nucleophilic displacement of 4‐chloronitrobenzene with the potassium phenolate of 5‐amino‐1‐naphthol in dimethylformamide, followed by hydrazine palladium‐catalyzed reduction. A series of novel aromatic polyimides containing asymmetrical diaryl ether segments were prepared from the diamine with various aromatic dianhydrides via a conventional two‐step thermal or chemical imidization method. The poly(amic acid) precursors had inherent viscosities of 1.21–1.99 dL/g, and all of them could be cast and thermally converted into transparent, flexible, and tough polyimide films. The polyimides derived from less stiff dianhydrides generally displayed higher solubility. The glass‐transition temperatures of these polyimides were recorded between 307 and 336 °C by differential scanning calorimetry, and the softening temperatures of the polymer films were 299–344 °C according to thermomechanical analysis. The polyimides showed insignificant decomposition before 520 °C in air or nitrogen. For a comparative study, two series of analogous polyimides based on symmetrical diamines such as 1,5‐diaminonaphthalene and 1,5‐bis(4‐aminophenoxy)naphthalene were also prepared and characterized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 331–341, 2005     

Synthesis and characterization of polyimides derived from (3‐amino‐2,4,6‐trimethylphenyl)‐(3′‐aminophenyl)methanone and aromatic dianhydrides

A series of new polyimides were prepared via the polycondensation of (3‐amino‐2,4,6‐trimethylphenyl)‐(3′‐aminophenyl)methanone and aromatic dianhydrides, that is, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride. The structures of the polyimides were characterized by Fourier transform infrared and NMR measurements. The properties were evaluated by solubility tests, ultraviolet–visible analysis, differential scanning calorimetry, and thermogravimetric analysis. The two different meta‐position‐located amino groups with respect to the carbonyl bridge in the diamine monomer provided it with an unsymmetrical structure. This led to a restriction on the close packing of the resulting polymer chains and reduced interchain interactions, which contributed to the solubility increase. All the polyimides except that derived from BPDA had good solubility in strong aprotic solvents, such as N‐methyl‐2‐pyrrolidinone, N,N′‐dimethylacetamide, N,N‐dimethylformamide, and dimethyl sulfone, and in common organic solvents, such as cyclohexanone and chloroform. In addition, these polyimides exhibited high glass‐transition values and excellent thermal properties, with an initial thermal decomposition temperature above 470 °C and glass‐transition temperatures in the range of 280–320 °C. The polyimide films also exhibited good transparency in the visible‐light region, with transmittance higher than 80% at 450 nm and a cutoff wavelength lower than 370 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1291–1298, 2006     

Polyimide containing internal acetylene units linked para to the aromatic ring

4,4′-Diaminodiphenylacetylene (p-intA) was reacted with 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and pyromellitic dianhydride (PMDA) in N-methyl-2-pyrrolidone (NMP) to give poly(amic acid) solution of moderate to high viscosity. Thermal imidization gave polyimide having acetylene units that are linked para to the aromatic connecting unit. Polyimide having acetylene units that are linked meta to the aromatic connecting unit also was prepared utilizing 3,3′-diaminodiphenylacetylene (m-intA) for comparison. The crosslinking behavior of the acetylene units was observed with DSC. Exotherm due to the crosslinking of the para-linked acetylene units appeared at ca. 340 to 380°C depending on the structure of polyimide, whereas meta-linked acetylene units appeared at lower temperature as 340–350°C. After thermal treatment at high temperature such as 350 or 400°C, the amount of the exotherm became smaller and finally disappeared on DSC, confirming the progress of crosslinking. Dynamic mechanical properties of the polyimide films show that glass transition temperature increased with higher heat treatment, also confirming the progress of crosslinking. Tensile properties of the polyimide films showed that rigid polyimide films consisting of p-intA with BPDA or PMDA have considerably higher modulus than those consisting of m-intA. Cold-drawing of the poly(amic acid) followed by imidization gave much higher modulus in the case of rigid polyimide. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2395–2402, 1997     

Synthesis and characterization of new fluorene‐based poly(ether imide)s

A novel bis(ether anhydride) monomer, 9,9‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]fluorene dianhydride (4), was synthesized from the nitrodisplacement of 4‐nitrophthalonitrile by the bisphenoxide ion of 9,9‐bis(4‐hydroxyphenyl)fluorene (1), followed by alkaline hydrolysis of the intermediate tetranitrile and dehydration of the resulting tetracarboxylic acid. A series of poly(ether imide)s bearing the fluorenylidene group were prepared from the bis(ether anhydride) 4 with various aromatic diamines 5a–i via a conventional two‐stage process that included ring‐opening polyaddition to form the poly(amic acid)s 6a–i followed by thermal cyclodehydration to the polyimides 7a–i. The intermediate poly(amic acid)s had inherent viscosities in the range of 0.39–1.57 dL/g and afforded flexible and tough films by solution‐casting. Except for those derived from p‐phenylenediamine, m‐phenylenediamine, and benzidine, all other poly(amic acid) films could be thermally transformed into flexible and tough polyimide films. The glass transition temperatures (T_g) of these poly(ether imide)s were recorded between 238–306°C with the help of differential scanning calorimetry (DSC), and the softening temperatures (T_s) determined by thermomechanical analysis (TMA) stayed in the range of 231–301°C. Decomposition temperatures for 10% weight loss all occurred above 540°C in an air or a nitrogen atmosphere. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1403–1412, 1999