Synthesis and Characterization of Fluorinated Polyimide Derived from 3,3′‐Diisopropyl‐4,4′‐diaminodiphenyl‐3′′,4′′‐difluorophenylmethane

A novel aromatic diamine monomer, 3,3′‐diisopropyl‐4,4′‐diaminodiphenyl‐3′′,4′′‐difluorophenylmethane (PAFM), was successfully synthesized by coupling of 2‐isopropylaniline and 3,4‐difluorobenzaldehyde. The aromatic diamine was adopted to synthesize a series of fluorinated polyimides by polycondensation with various dianhydrides: pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (ODPA) and 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) via the conventional one‐step method. These polyimides presented excellent solubility in common organic solvents, such as N,N‐dimethylformamide (DMF), N,N‐dimethyl acetamide (DMAc), dimethyl sulfoxide (DMSO), N‐methyl‐2‐pyrrolidone (NMP), chloroform (CHCl₃), tetrahydrofuran (THF) and so on. The glass transition temperatures (T_g) of fluorinated polyimides were in the range of 260–306°C and the temperature at 10% weight loss in the range of 474–502°C. Their films showed the cut‐off wavelengths of 330–361 nm and higher than 80% transparency in a wavelength range of 385–463 nm. Moreover, polymer films exhibited low dielectric properties in the range of 2.76–2.96 at 1 MHz, as well as prominent mechanical properties with tensile strengths of 66.7–97.4 MPa, a tensile modulus of 1.7–2.1 GPa and elongation at break of 7.2%–12.9%. The polymer films also showed outstanding hydrophobicity with the contact angle in the range of 91.2°–97.9°.     

Organosoluble polyimides and copolyimides based on 1,1‐bis[4‐(4‐aminophenoxy)phenyl]‐1‐phenylethane and aromatic dianhydrides

1,1‐Bis[4‐(4‐aminophenoxy)phenyl]‐1‐phenylethane (BAPPE) was prepared through nucleophilic substitution reaction of 1,1‐bis(4‐hydroxyphenyl)‐1‐phenylethane and p‐chloronitrobenzene in the presence of K₂CO₃ in N,N‐dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. Novel organosoluble polyimides and copolyimides were synthesized from BAPPE and six kinds of commercial dianhydrides, including pyromellitic dianhydride (PMDA, I_a ), 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA, I_b ), 3,3′,4,4′‐ biphenyltetracarboxylic dianhydride (BPDA, I_c ), 4,4′‐oxydiphthalic anhydride (ODPA, I_d ), 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride (DSDA, I_e ) and 4,4′‐hexafluoroisopropylidenediphthalic anhydride (6FDA, I_f ). Differing with the conventional polyimide process by thermal cyclodehydration of poly(amic acid), when polyimides were prepared by chemical cyclodehydration with N‐methyl‐2‐pyrrolidone as used solvent, resulted polymers showed good solubility. Additional, I_a,b were mixed respectively with the rest of dianhydrides (I_c–f) and BAPPE at certain molar ratios to prepare copolyimides with arbitrary solubilities. These polyimides and copolyimides were characterized by good mechanical properties together with good thermal stability. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2082–2090, 2000     

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).     

Syntheses and properties of organosoluble polyimides based on 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐4, 7‐methanohexahydroindan

A series of organosoluble aromatic polyimides (PIs) was synthesized from 5,5′‐bis[4‐(4‐aminophenoxy)phenyl]‐4,7‐methanohexahydroindan (3) and commercial available aromatic dianhydrides such as 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (ODPA), 4,4′‐sulfonyl diphthalic anhydride (SDPA), or 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropanic dianhydride (6FDA). PIs (III_c–f), which were synthesized by direct polymerization in m‐cresol, had inherent viscosities of 0.83–1.05 dL/g. These polymers could easily be dissolved in N,N′‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), N,N‐dimethylformamide (DMF), pyridine, m‐cresol, and dichloromethane. Whereas copolymerization was proceeded with equivalent molar ratios of pyromellitic dianhydride (PMDA)/6FDA, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA)/6FDA, or BTDA/SDPA, or ½ for PMDA/SDPA, copolyimides (co‐PIs), derived from 3 and mixed dianhydrides, were soluble in NMP. All the soluble PIs could form transparent, flexible, and tough films, and they showed amorphous characteristics. These films had tensile strengths of 88–111 MPa, elongations at break of 5–10% and initial moduli of 2.01–2.67 GPa. The glass transition temperatures of these polymers were in the range of 252–311°C. Except for III_e, the 10% weight loss temperatures (T_d) of PIs were above 500°C, and the amount of carbonized residues of the PIs at 800°C in nitrogen atmosphere were above 50%. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1681–1691, 1999     

Polyimides from isomeric diphenylthioether dianhydrides

3,3′,4,4′‐Diphenylthioether dianhydride (4,4′‐TDPA), 2,3,3′,4′‐diphenylthioether dianhydride (3,4′‐TDPA), and 2,2′,3,3′‐diphenylthioether dianhydride (3,3′‐TDPA) were synthesized from 3‐chlorophthalic anhydride and 4‐chlorophthalic anhydride. A series of polyimides derived from the isomeric diphenylthioether dianhydrides with several diamines were prepared. The properties, such as the solubility, thermal and mechanical behavior, dynamic mechanical behavior, wide‐angle X‐ray diffraction, and permeability to some gases, were compared among the isomeric polyimides. Both 3,3′‐TDPA‐ and 3,4′‐TDPA‐based polyimides had good solubility in polar aprotic solvents and phenols. The 5% weight loss temperatures of all the obtained polyimides was near 500 °C in nitrogen. The glass‐transition temperatures decreased according to the order of the polyimides based on 3,3′‐TDPA, 3,4′‐TDPA, and 4,4′‐TDPA. The 3,4′‐TDPA‐based polyimides had the best permeability and lowest permselectivity, whereas the 4,4′‐TDPA‐based polyimides had the highest permselectivity and the lowest permeability of the three isomers. Furthermore, the rheological properties of thermoplastic polyimide resins based on the isomeric diphenylthioether dianhydrides were investigated, and they showed that polyimide 3,4′‐TDPA/4,4‐oxydianiline had the lowest melt viscosity among the isomers; this indicated that the melt processibility had been greatly improved. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 959–967, 2006     

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     

Amine–quinone polyimides

Two dianiline monomers were prepared by the reaction of either 4,4′‐methylenedianiline or 4,4′‐oxydianiline with 1,4‐benzoquinone. These monomers were used to synthesize a series of amine–quinone polyimides by condensation with either 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride or 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride to make the corresponding polyamic acid. The polyamic acids were converted to the polyimides by thermal imidization at 290 °C. The amine–quinone polyimides gave freestanding films with tensile strengths in the range of 90 to 150 MPa and Young's moduli of 0.9 to 1.5 GPa. The thermal decomposition temperature under nitrogen was 440 to 480 °C and the glass‐transition temperature was in the range of 280 to 310 °C. The amine–quinone polyimides had the excellent thermal and mechanical properties that one expects for polyimides. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4044–4049, 2001     

Polyimides from isomeric oxydiphthalic anhydrides

2,2′,3,3′‐Oxydiphthalic dianhydride (2,2′,3,3′‐ODPA) and 2,3,3′,4′‐ODPA were synthesized from 3‐chlorophthalic anhydride with 2,3‐xylenol and 3,4‐xylenol, respectively. Their structures were determined via single‐crystal X‐ray diffraction. A series of polyimides derived from isomeric ODPAs with several diamines were prepared in dimethylacetamide (DMAc) with the conventional two‐step method. Matrix‐assisted laser desorption/ionization time‐of‐flight spectra showed that the polymerization of 2,2′,3,3′‐ODPA with 4,4′‐oxydianiline (ODA) has a greater trend to form cyclic oligomers than that of 2,3,3′,4′‐ODPA. Both 2,2′,3,3′‐ODPA and 2,3,3′,4′‐ODPA based polyimides have good solubility in polar aprotic solvents such as DMAc, dimethylformamide, and N‐methylpyrrolidone. The 5% weight‐loss temperatures of all polyimides were obtained near 500 °C in air. Their glass‐transition temperatures measured by dynamic mechanical thermal analysis or differential scanning calorimetry decreased according to the order of polyimides on the basis of 2,2′,3,3′‐ODPA, 2,3,3′,4′‐ODPA, and 3,3′,4,4′‐ODPA. The wide‐angle X‐ray diffraction of all polyimide films from isomeric ODPAs and ODA showed some certain extent of crystallization after stretching. Rheological properties revealed that polyimide (2,3,3′,4′‐ODPA/ODA) has a comparatively lower melt viscosity than its isomers, which indicated its better melt processability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3249–3260, 2003     

Synthesis and characterization of novel fluorinated aromatic polyimides derived from 1,1‐bis(4‐amino‐3,5‐dimethylphenyl)‐1‐(3,5‐ditrifluoromethylphenyl)‐2,2,2‐trifluoroethane and various aromatic dianhydrides

A novel fluorinated aromatic diamine, 1,1‐bis(4‐amino‐3,5‐dimethylphenyl)‐1‐(3,5‐ditrifluoromethylphenyl)‐2,2,2‐trifluoroethane (9FMA), was synthesized by the coupling reaction of 3′,5′‐ditrifluoromethyl‐2,2,2‐trifluoroacetophenone with 2,6‐dimethylaniline under the catalysis of 2,6‐dimethylaniline hydrochloride. A series of fluorinated aromatic polyimides were synthesized from 9FMA and various aromatic dianhydrides, including pyromellitic dianhydride, 3,3′4,4′‐biphenyl tetracarboxylic dianhydride, 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′‐hexafluoroisopropylidene diphthalic anhydride, via a high‐temperature, one‐stage imidization process. The inherent viscosities of the polyimides ranged from 0.37 to 0.74 dL/g. All the polyimides were quickly soluble in many low‐boiling‐point organic solvents such as tetrahydrofuran, chloroform, and acetone as well as some polar organic solvents such as N‐methyl‐2‐pyrrolidinone, N,N′‐dimethylacetamide, and N,N′‐dimethylformamide. Freestanding fluorinated polyimide films could be prepared and exhibited good thermal stability with glass‐transition temperatures of 298–334 °C and outstanding mechanical properties with tensile strengths of 69–102 MPa and elongations at break of 3.3–9.9%. Moreover, the polyimide films possessed low dielectric constants of 2.70–3.09 and low moisture absorption (<0.58%). The films also exhibited good optical transparency with a cutoff wavelength of 303–351 nm. One polyimide (9FMA/BTDA) also exhibited an intrinsic negative photosensitivity, and a fine pattern could be obtained with a resolution of 5 μm after exposure at the i‐line (365‐nm) wavelength. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2665–2674, 2006     

Synthesis and properties of fluorinated polyimides from a new unsymmetrical diamine: 1,4‐(2′‐Trifluoromethyl‐4′,4′‐diaminodiphenoxy)benzene

A new aromatic, unsymmetrical ether diamine with a trifluoromethyl pendent group, 1,4‐(2′‐trifluoromethyl‐4′,4″‐diaminodiphenoxy)benzene, was successfully synthesized in three steps with hydroquinone as a starting material and polymerized with various aromatic tetracarboxylic acid dianhydrides, including 4,4′‐oxydiphthalic anhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, 2,2′‐bis(3,4‐dicarboxyphenyl)‐hexafluoropropane dianhydride, and pyromellitic dianhydride, via a conventional two‐step thermal or chemical imidization method to produce a series of fluorinated polyimides. The polyimides were characterized with solubility tests, viscosity measurements, IR, ¹H NMR, and ¹³C NMR spectroscopy, X‐ray diffraction studies, and thermogravimetric analysis. The polyimides had inherent viscosities of 0.56–0.77 dL/g and were easily dissolved in both polar, aprotic solvents and common, low‐boiling‐point solvents. The resulting strong and flexible polyimide films exhibited excellent thermal stability, with decomposition temperatures (at 5% weight loss) above 522 °C and glass‐transition temperatures in the range of 232–272 °C. Moreover, the polymer films showed outstanding mechanical properties, with tensile strengths of 74.5–121.7 MPa, elongations at break of 6–13%, and initial moduli of 1.46–1.95 GPa, and good dielectric properties, with low dielectric constants of 1.82–2.53 at 10 MHz. Wide‐angle X‐ray diffraction measurements revealed that these polyimides were predominantly amorphous. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced microelectronic applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6836–6846, 2006     

Aromatic polyamides and polyimides derived from 3,3′-diaminobiphenyl: Synthesis,characterization, and molecular simulation study

In this article a new synthesis of 3,3′-diaminobiphenyl (3,3′-DABP) is described, along with the preparation and characterization of polyamides and polyimides based on it. Reactivity of this monomer was calculated by a molecular simulation study, using ab initio quantum-mechanical methods. Terephthaloyl and isophthaloyl chloride were used for the synthesis of polyamides, while 3,3′,4,4′-biphenylenetetracarboxylic acid dianhydride and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride were used for the synthesis of polyimides. Medium to high molecular weight polymers were attained, with inherent viscosities near or higher than 1.0 dL/g, the solubility of the 3,3′-DABP polymers was much better than that of the homologous polymers from benzidine (4,4′-DABP), the glass-transition temperatures were lower, by about 40°C, and the thermal resistance, as measured by thermogravimetry, was virtually the same. Amorphous films, made from cast polymer solutions, showed excellent mechanical properties, comparable to conventional aromatic polyamides and polyimides. Theoretical calculations demonstrated that the radius of giration, end-to-end distance and density of poly(3,3′-DABP-isophthalamide) were lower than those of poly(4,4′-DABP-isophthalamide), as a consequence of the chain folding induced in the backbone by the m-substitution in 3,3′-DABP. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4646–4655, 1999     

Fully imidized soluble polyimides based on a novel dianhydride: 2,2′-dichloro-4,4′,5,5′-benzophenone tetracarboxylic dianhydride

We have synthesized a novel dianhydride, 2,2′-dichloro-4,4′,5,5′-benzophenone tetracarboxylic dianhydride (DCBTDA). Polyimides were synthesized with DCBTDA or 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and several relatively rigid meta- and para- substituted mononuclear diamines. The BTDA based systems were insoluble in dipolar, aprotic solvents whereas the DCBTDA based polymers displayed enhanced solubility in these solvents. The thermal stability of these polyimides was excellent as measured by 5% weight loss decomposition. The T_g's of the polymers were all above 290°C.     

Synthesis and characterization of photosensitive polyimides from methylthiomethyl-substituted 4,4′-diaminodiphenylmethanes and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride

A series of novel polyimides are synthesized by the reaction of 3,3′,4,4′-benzophenonete-tracarboxylic dianhydride (BTDA) with four methylthiomethyl-substituted aromatic diamines: 3-methylthiomethyl-4,4′-diaminodiphenylmethane ( I ), 3,3′-dimethylthiomethyl-4,4′-diaminodiphenylmethane ( II ), 3,3′,5-trimethylthiomethyl-4,4′-diaminodiphenylmethane ( III ), and 3,3′,5,5′-tetramethylthiomethyl-4,4′-diaminodiphenylmethane ( IV ) in refluxing m-cresol. The polyimide of diamine I and BTDA carrying only one pendant methylthiomethyl group in a repeating unit is readily soluble in m-cresol, chloroform, and polar aprotic solvents. Increasing the number of the pendant group results in higher solubility. These fully imidized polyimides are also intrinsically photosensitive. The fraction of photoreactive benzophenone sites that relates to the rate and degree of completion of photocrosslinking reaction increases systematically with the increase of the pendant group content. As the average number of the pendant group in a repeating unit reaches 3, 63% of benzophenone sites are found to be photoreactive. These methylthiomethyl-substituted polyimides possess moderate tensile strength which falls in the range of 67–81 MPa. As a result of the increase of methylthiomethyl content, this type of polyimide reveals higher glass transition temperature but lower thermal stability due to the considerable dimension of the pendant group and the ready cleavage nature of the C? S bond. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of hyperbranched polyimides with good organosolubility and thermal properties based on a new triamine and conventional dianhydrides

A triamine monomer, 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB), was synthesized from phloroglucinol and 4‐chloronitrobenzene, and it was successfully polymerized into soluble hyperbranched polyimides (HB PIs) with commercially available dianhydrides: 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA). Different monomer addition methods and different monomer molar ratios resulted in HB PIs with amino or anhydride end groups. From ¹H NMR spectra, the degrees of branching of the amino‐terminated polymers were estimated to be 0.65, 0.62, and 0.67 for 6FDA–TAPOB, ODPA–TAPOB, and BTDA–TAPOB, respectively. All polymers showed good thermal properties with 10% weight‐loss temperatures (T₁₀'s) above 505 °C and glass‐transition temperatures (T_g's) of 208–282 °C for various dianhydrides. The anhydride‐terminated HB PIs showed lower T₁₀ and T_g values than their amino‐terminated counterparts. The chemical conversion of the terminal amino or anhydride groups of the 6FDA‐based polyimides into an aromatic imido structure improved their thermal stability, decreased their T_g, and improved their solubility. The HB PIs had moderate molecular weights with broad distributions. The 6FDA‐based HB PIs exhibited good solubility even in common low‐boiling‐point solvents such as chloroform, tetrahydrofuran, and acetone. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3804–3814, 2002     

New organo‐soluble aromatic polyimides based on 3,3′,5,5′‐tetrabromo‐2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and aromatic diamines

New aromatic tetracarboxylic dianhydride, having isopropylidene and bromo‐substituted arylene ether structure 3,3′,5,5′‐tetrabromo‐2,2‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride, was synthesized by the reaction of 4‐nitrophthalonitrile with 3,3′,5,5′‐tetrabromobisphenol A, followed by alkaline hydrolysis of the intermediate bis(ether dinitrile) and subsequent dehydration of the resulting bis(ether diacid). The novel aromatic polyetherimides having inherent viscosities up to 1.04 dL g⁻¹ were obtained by either a one‐step or a conventional two‐step polymerization process starting from the bis(ether anhydride) and various aromatic diamines. All the polyimides showed typical amorphous diffraction patterns. Most of the polyimides were readily soluble in common organic solvents such as N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), pyridine, and even in less polar solvents like chloroform and tetrahydrofuran (THF). These aromatic polyimides had glass transition temperatures in the range of 256–303°C, depending on the nature of the diamine moiety. Thermogravimetric analysis (TGA) showed that all polymers were stable, with 10% weight loss recorded above 470°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1673–1680, 1999     

Comparative study on polyimides from isomeric 3,3′‐, 3,4′‐, and 4,4′‐linked bis(thioether anhydride)s

Three isomeric bis(thioether anhydride) monomers, 4,4′‐bis(2,3‐dicarboxyphenylthio) diphenyl ketone dianhydride (3,3′‐PTPKDA), 4,4′‐bis(3,4‐dicarboxyphenylthio) diphenyl ketone dianhydride (4,4′‐PTPKDA), and 4‐(2,3‐dicarboxyphenylthio)‐4′‐(3,4‐dicarboxyphenylthio) diphenyl ketone dianhydride (3,4′‐PTPKDA), were prepared through multistep reactions. Their structures were determined via Fourier transform infrared, NMR, and elemental analysis. Three series of polyimides (PIs) were prepared from the obtained isomeric dianhydrides and aromatic diamines in N‐methyl‐2‐pyrrolidone (NMP) via the conventional two‐step method. The PIs showed excellent solubility in common organic solvents such as chloroform, N,N‐dimethylacetamide, and NMP. Their glass‐transition temperatures decreased according to the order of PIs on the basis of 3,3′‐PTPKDA, 3,4′‐PTPKDA, and 4,4′‐PTPKDA. The 5% weight loss temperatures (T_5%) of all PIs in nitrogen were observed at 504–519 °C. The rheological properties of isomeric PI resins based on 3,3′‐PTPKDA/4,4′‐oxydianiline/phthalic anhydride showed lower complex viscosity and better melt stability compared with the corresponding isomers from 4,4′‐ and 3,4′‐PTPKDA. In addition, the PI films based on three isomeric dianhydrides and 2,2′‐bis(trifluoromethyl)benzidine had a low moisture absorption of 0.27–0.35%. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and properties of new polyimides derived from 1,5-bis(4-aminophenoxy)naphthalene and aromatic tetracarboxylic dianhydrides

Novel aromatic polyimides containing bis(phenoxy)naphthalene units were synthesized from 1,5-bis(4-aminophenoxy)naphthalene (APN) and various aromatic tetracarboxylic dianhydrides by the usual two-step procedure that included ring-opening polyaddition in a polar solvent such as N,N-dimethylacetamide (DMAc) to give poly(amic acid)s, followed by cyclodehydration to polyimides. The poly(amic acid)s had inherent viscosities between 0.72 and 1.94 dL/g, depending on the tetracarboxylic dianhydrides used. Excepting the polyimide IVb obtained from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), all other polyimides formed brown, flexible, and tough films by casting from the poly(amic acid) solutions. The polyimide synthesized from BPDA was characterized as semicrystalline, whereas the other polyimides showed amorphous patterns as shown by the x-ray diffraction studies. Tensile strength, initial moduli, and elongation at break of the APN-based polyimide films ranged from 105–135 MPa, 1.92–2.50 GPa, and 6–7%, respectively. These polyimides had glass transition temperatures between 228 and 317°C. Thermal analyses indicated that these polymers were fairly stable, and the 10% weight loss temperatures by TGA were recorded in the range of 543–574°C in nitrogen and 540–566°C in air atmosphere, respectively. © 1993 John Wiley & Sons, Inc.     

Synthesis and properties of polyimides from thianthrene-2,3,7,8-tetracarboxylic dianhydride-5,5,10,10-tetraoxide

Thianthrene - 2,3,7,8 - tetracarboxylic dianhydride - 5,5,10,10 - tetraoxide (TADATO), a dianhydride having two sulfonyls between two phenyl rings, was synthesized and polymerized with several diamines by a two-step method. Tough polyimide membranes were obtained with flexible diamines but not with rigid diamines. Most of TADATO-based polyimides are soluble in polar solvents such as N,N-dimethylacetamide and N-methyl-2-pyrrolidone. IR study confirmed that almost complete imidization of TADATO-based poly(amic acid) membranes could be achieved by thermal treatment at 100, 200, and 300°C for each 1 h. In a series of polyimides based on 4,4′-oxydianiline, the polyimide from TADATO showed higher gas permeability coefficient of CO₂ and higher selectivities of CO₂/N₂ and CO₂/CH₄ than those of polyimides from pyromellitic dianhydride and 3,3′,4,4′-biphenyltetracarboxylic dianhydride, and was comparable to that from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36 : 485–494, 1998     

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.     

Synthesis and properties of aromatic polyimides derived from 2,2,′3,3′‐biphenyltetracarboxylic dianhydride

2,2,′3,3′‐Biphenyltetracarboxylic dianhydride (2,2,′3,3′‐BPDA) was prepared by a coupling reaction of dimethyl 3‐iodophthalate. The X‐ray single‐crystal structure determination showed that this dianhydride had a bent and noncopolanar structure, presenting a striking contrast to its isomer, 3,3,′4,4′‐BPDA. This dianhydride was reacted with aromatic diamines in a polar aprotic solvent such as N,N‐dimethylacetamide (DMAc) to form polyamic acid intermediates, which imidized chemically to polyimides with inherent viscosities of 0.34–0.55 dL/g, depending on the diamine used. The polyimides from 2,2,′3,3′‐BPDA exhibited a good solubility and were dissolved in polar aprotic solvents and polychlorocarbons. These polyimides have high glass transition temperatures above 283°C. Thermogravimetric analyses indicated that these polyimides were fairly stable up to 500°C, and the 5% weight loss temperatures were recorded in the range of 534–583°C in nitrogen atmosphere and 537–561°C in air atmosphere. All polyimides were amorphous according to X‐ray determination. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1425–1433, 1999