Synthesis of semiaromatic polyimides from aromatic diamines containing adamantyl units and alicyclic dianhydrides

We prepared new semiaromatic polyimides from alicyclic dianhydrides and aromatic diamines containing adamantyl and biadamantyl units. Polycondensations were performed in 1‐methyl‐2‐pyrrolidinone at room temperature for 7 h and then 80 °C for 23 h, giving poly(amic acid)s with inherent viscosities up to 0.58 dL/g. Poly(amic acid)s were converted to corresponding poly(imide)s by thermal treatment. Poly(imide)s showed relatively high thermal stability (5% weight loss around 450 °C) and low dielectric constants (2.69–2.79). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 144–150, 2004     

New polymer systems based on alicyclic polyimides

Specific features of modification of some alicyclic polyimides with polyamido acids derived from aromatic tetracarboxylic acid dianhydrides were studied. The possibility of preparing new polymer systems with improved characteristics was demonstrated.     

Study of thermochemical conversions of alicyclic polyimides

The thermochemical conversions of certain polyimides obtained by the polycondensation of dianhydrides of alicyclic tetracarboxylic acids and 4,4-diaminodiphenyl oxide were studied by different methods of thermal analysis (thermogravimetry, mass-spectrometric evolved gas analysis, and pyrolytic gas chromatography). The thermal dissociation of dianhydride fragments according to the reverse reaction of retrodiene synthesis is the basic reaction that determines the thermal stabilities of the polymers studied. It is shown that the absence of endoethylene bonding or its substitution by oxygen in the dianhydride fragments leads to increases in the thermal stabilities of alicyclic polyimides.

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Zusammenfassung Thermochemische Umwandlungen einiger Polyimide, die durch Polykondensation der Dianhydride alicyclischer Tetracarbonsäuren mit 4,4-Diaminodiphenyloxid dargestellt waren, wurden durch verschiedene thermoanalytische Methoden (TG, massenspektrometrische EGA und Pyrolyse-Gaschromatographie) untersucht. Die thermische Spaltung der Dianhydrid-Komponente nach einer Retro-Diensynthese ist die Hauptreaktion, die die thermische Stabilität der Polymeren bestimmt. Bei Abwesenheit der endo-Ethylen-Bindung in der Dianhydrid-Komponente oder Substitution durch eine Etherbindung wird die thermische Stabilität von Polyimiden mit alicyclischen Baugruppen erhöht.

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The authors would like to thank Yu. A. Sazanov and L. A. Shibaev (IVS AN SSSR, Leningrad) for help in the mass-spectrometric thermal analysis of the polymers.     

Soluble and transparent polyimides from unsymmetrical diamine containing two trifluoromethyl groups

A new unsymmetrical diamine monomer containing two trifluoromethyl (CF₃) groups is prepared from 2‐bromo‐5‐nitro‐1,3‐bis(trifluoromethyl)benzene. The monomer is polymerized with typical dianhydrides, in this case PMDA, BPDA, BTDA, ODPA, and 6‐FDA, using a one‐pot synthetic method to obtain corresponding polyimides. All of the prepared polyimides are readily soluble in many organic solvents and can be solution‐cast into transparent, flexible, and tough films. These films have a UV–vis absorption cut‐off wavelength at 340–375 nm and light transparencies of 87–91% at a wavelength of 550 nm. Incorporation of two CF₃ groups unsymmetrically into rigid polyimides improves their solubility and transparencies without decreasing their physical properties. The polymers exhibit high thermal stability with 5% weight loss at temperatures ranging from 534 to 593 °C in nitrogen and from 519 to 568 °C in air, and high glass transition temperatures (T_g) above > 300 °C depending on their molecular structures. They also have a coefficient of thermal expansion (CTE) value of 46–69 ppm/°C. In addition, they show low refractive indices in the range of 1.535–1.602 at a wavelength of 633 nm due to the unsymmetrical incorporation effect of the two CF₃ groups. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4413–4422     

Soluble polyimides from a semi-aliphatic diamine containing ester,amide and ether groups

A diamine was synthesized by two successive reactions.Nucleophilic reaction of 4-hydroxybenzoic acid with terephthaloyl chloride yielded terephthaloyl bis(4-oxybenzoic) acid.Then reaction of this compound with 1,8-diamino-3,6- dioxaoctane via Yamazaki method resulted in preparation of diamine named terephthalic acid bis(4-{2-[2-(2-amino ethoxy)ethoxy]ethyl carbamoyl}phenyl) ester.After fully characterization it was used to prepare new polyimides through polycondensation with different dianhydrides using trimethylchlorosilane.Characterization of polymers was achieved by common methods and their physical properties including inherent viscosity,thermal behavior,thermal stability,crystallinity and solubility were studied.Prepared polyimides showed improved solubility and good thermal stability.     

Organosoluble and transparent polyimides derived from alicyclic dianhydride and aromatic diamines

Organosoluble polyimides were synthesized with the alicyclic dianhydride 1,8‐dimethylbicyclo[2,2,2]oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride and aromatic diamines. The polyimides possessed good solubility both in strong dipolar solvents and in common solvents; the thermal decomposition temperature of the polyimides exceeded 420 °C. Strong and flexible films of the polyimides, with the cutoff of ultraviolet–visible absorption lower than 310–320 nm, exhibited good features as the alignment layers for nematic liquid crystals with pretilt angles of 1.5–2.9°. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 110–119, 2002     

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

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

Synthesis of optically active alicyclic polyimides from a chiral,nonracemic dianhydride

Optically active alicyclic polyimides were prepared for the first time from (?)‐[1S*,5R*,6S*]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐ 2′,5′‐dione) [(?)‐DAn] via polycondensation with diamines and subsequent chemical or thermal imidization. The dianhydride (?)‐DAn was synthesized by an asymmetric Diels–Alder reaction of a chiral itaconic acid derivative as a key step. Colorless or slightly yellow flexible films were obtained for the (?)‐DAn‐derived polyimides {PI[(?)‐DAn]s}. PI[(?)‐DAn]s showed good solubility toward dipolar aprotic solvents and pyridine. For 1,4‐dioxane and chloroform, the optically active polyimides showed slightly better solubility than the corresponding polyimides prepared from rac‐DAn [PI(rac‐DAn)s]. PI[(?)‐DAn]s showed glass‐transition temperatures of 267–268 °C and 10% weight‐loss temperatures of 416–424 °C in nitrogen. These values were almost identical to those of PI(rac‐DAn)s. The circular dichroism spectra of PI[(?)‐DAn]s showed exciton coupling patterns indicating that to some extent these polyimides had a higher order structure in solution. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4038–4044, 2002     

Polyimides with alicyclic diamines. II. Hydrogen abstraction and photocrosslinking reactions of benzophenone-type polyimides

Photosensitive polyimides with alicyclic diamines and benzophenone moiety were prepared by reactions of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with diamines in aprotic solvents, followed by thermal or chemical imidizations. Among them the polyimide from BTDA and bis(4-amino-3-methylcyclohexyl) methane (DMDHM) can be dissolved in several organic solvents such as dichloromethane, tetrachloroethane, and N-methyl-2-pyrrolidone (NMP). In order to compare properties of the polyimides with alicyclic diamines with those of corresponding aromatic polyimides, the UV absorption spectra and fluorescence spectra of these polyimides and their model compounds were investigated. No occurrence of charge transfer at photoexcited states was ascertained for the polyimides with alicyclic diamines. The hydrogen abstraction and crosslinking during photoirradiation have been studied to learn the influence of the elimination of charge transfer process in these photosensitive polyimides. The quantum yield of hydrogen abstraction for the model compound of alicyclic polyimides is 0.56 in THF measured with HPLC. The quantum yield for the photocrosslinking reaction of the solvent-soluble polyimide with alicyclic diamine, PI(BTDA/DMDHM), was determined to be 0.004 in air from gel permeation chromatography (GPC) measurement, which is four times higher than that for photosensitive polyimides with aromatic diamines. © 1994 John Wiley & Sons, Inc.     

Synthesis of aliphatic polyimides containing adamantyl units

Aliphatic polyimides containing adamantyl units (APIs) were prepared by the poly(addition/condensation) of a dianhydride bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic 2,3 : 5,6-dianhydride with a rigid diamine, 1,3-diaminoadamantane or 3,3′-diamino-1,1′-biadamantyl, and a flexible diamine, 4,4′-methylenebis(cyclohexylamine) or 1,4-cyclohexanediamine. One-step polymerizations were conducted at 80–200°C in m-cresol, producing APIs with inherent viscosities up to 0.53 dL g⁻¹. These APIs are soluble in haloalkanes, m-cresol, and sulfuric acid and show high thermal stability and excellent transparency. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3584–3590, 1999     

Transport properties of polyimides containing phenylquinoxaline moieties

The gas permeabilities of a number of new structurally related polyimides containing phenylquinoxaline moieties were studied for the first time. The test polymers had different dianhydride units, whereas their diamine components differed in the presence of flexible ether bonds-O-in the main chain, a structure that is reflected in the effective packing of chains and, as a result, in transport parameters. The permeability, diffusion, and solubility coefficients for the gases H₂, He, O₂, N₂, CO, CO₂, and CH₄, as well as the ideal separation factors for gas pairs, were determined. The transport characteristics of polymers were compared within the given polymer series and with published data for other polymer series.     

Soluble and transparent polyimides with high Tg from a new diamine containing tert‐butyl and fluorene units

A novel diamine monomer 1 , 4,4'‐(9H‐fluorene‐9,9‐diyl)‐bis(2‐tert‐butylaniline), was synthesized from 9‐fluorenone and 2‐tert‐butylaniline by the condensation reaction. Then it was polymerized with several commercial aromatic dianhydrides, respectively, to produce polyimides (PIs) by the one‐pot method. The number‐averaged molecular weights of the resulting PIs are in the range of (4.54–8.82) × 10⁴ with polydispersity indices from 2.51 to 4.33 by gel permeation chromatography measurement. They are soluble in many organic solvents and can form transparent and tough films by solution‐casting. The cut‐off wavelengths of UV–vis absorption for the PI films are below 360 nm, which are much lower than that of Kapton film. The light transparency of them is above 90% in the visible light range from 400 to 760 nm. They also display relatively low dielectric constants (from 2.79 to 3.00), low water absorption rates (<1%), and high tensile strength (> 50 MPa). Their excellent solubility and transparency can be attributed to the incorporation of tert‐butyl groups and fluorene units into the rigid backbones of PIs. Simultaneously, they still maintain the high thermal stability (the 5% weight loss temperature in the range from 526 to 539 °C in nitrogen) and the high glass transition temperatures (T_g > 340 °C). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 976–984     

Crosslinkable aromatic polyimides containing 2,3-dicyanopyrazine rings

New crosslinkable aromatic polyimides were synthesized from 2,3-dicyano-5,6-di(aminophenyl)pyrazine ( 1b ) and 2,3-dicyanopyrazino [5,6–9,10] diaminophenanthrene ( 2b ). They were characterized by viscosimetry, IR, NMR, x-ray, DTA, TMA, TGA, and isothermal gravimetric analysis. The polyimides derived from 1b were amorphous whereas those prepared from 2b showed microcrystalline or crystalline character. The polymers were soluble in polar aprotic solvents (DMF, NMP, DMSO) at ambient temperature or upon heating. They dissolved also completely or partially in certain hot inorganic and organic acids (H₂SO₄, CCl₃COOH). Their glass transition temperatures were in the range of 257–370°C. The crosslinked polymers obtained after an appropriate thermal treatment, were stable up to 397–426°C in N₂ or air and afforded anaerobic char yields of 62–75% at 800°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1303–1311, 1997     

Concept of a sterically active environment in alicyclic structures

By seeking analogies in behavior between aliphatic and alicyclic carboxylic acids, it is possible to determine the sterically active sites of the latter.     

Thermo-oxidatively stable polyimides and their chemical structures

A series of aromatic diamines having ether and/or carbonyl moieties in their structures were synthesized. By using these synthesized diamines and commercially available tetracarboxylic dianhydrides, various kinds of polyimides having ether and/or carbonyl moieties were synthesized. The thermo-oxidative stability of the obtained polyimides was investigated by focusing on the chemical structures of their repeating structure units. The reason for the improved thermo-oxidative stability of the ether–carbonyl polyimide structure was explained by an electronically balanced condition, i.e., the balance of electron donor moiety (—O—) and electron acceptor moiety (—CO—) in a chemical structure, and the degree of electron deficiency of the benzene–imide ring structure. The possibility of the formation of a charge transfer complex (CT-complex) was also mentioned as an explanation of the improved thermo-oxidative stability of ether–carbonyl polyimide structures. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1717–1723, 1998     

Comparative study of polyimides containing different flexible linkages

Two series of polyimides were synthesized based on different aromatic dianhydrides containing various flexible linkages and two aromatic diamines containing ether and nitrile groups. The structure of the polymers was confirmed by FTIR and ¹H NMR spectroscopy. The correlation between some physical properties, such as solubility, thermal stability and glass transition temperature, and conformational rigidity parameters, such as Kuhn segment, characteristic ratio and rigidity parameter p, was studied.     

Electroluminescent properties of anthracene‐containing polyimides

Optical and electroluminescent properties of a new soluble anthracene‐containing polyimide (ACPI) was studied. Solubility of ACPI in organic solvents allows direct spin casting of the polymer films exhibiting intense photo‐ and electroluminescence (EL) in the visible range. This non‐conjugated polymer was used as emitting and electron‐hole transporting layers in polymer light‐emitting devices (LEDs). EL properties of the uni‐ and bilayer LEDs are discussed in terms of the band structure, bipolar transport and electron donor‐acceptor interactions. Copyright © 2000 John Wiley & Sons, Ltd.     

Synthesis and characterization of polyimides containing heterocyclic units

Five new polyimides containing phenoxaphosphine as well as dibenzothiophene, phenoxathiin, and thianthrene units have been synthesized from 10-phenylphenoxaphosphine-2,3,7,8-tetracarboxylic dianhydride-10-oxide and heterocyclic diamines by the cyclopolycondensation method. These polyimides had inherent viscosities in the 0.75–1.10 dL/g range in conc. H₂SO₄ at 30°C. All the polymers were characterized by elemental analysis, density, solubility, crystallinity, IR spectra, and thermal methods.