Study of the formation of polyimide from complexes of benzophenonetetracarboxylic acid diester with different diamines. 3. Dielectric study of thermal imidization

Dielectric loss peaks caused by thermal imidization were observed for the three complexes of benzophenonetetracarboxylic acid dimethyl ester (BZPE) with different diamines. The mechanism of the formation of imide rings from complexes with hydrogen bonds and with separated charges was specified. The specific features of thermal imidization of the BZPE·diaminopyridine dimeric complex were confirmed and it was shown that heat treatment of the complex of BZPE with hexamethylenediamine yields a softening polyimide and thermal imidization takes place at lower temperatures.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 534–539, March, 1990.     

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.     

Investigation of the process of polyimide formation from complexes of the diester of benzophenonetetracarboxylic acid with diamines

The kinetics of thermal imidization of the H-complexes derived from the diethyl ester of 3,3,4,4-benzophenonetetracarboxylic acid (EBZP) and various diamines have been studied. A comparison of kinetic parameters obtained for the imidization of H-complexes based on ethyl or methyl esters of this acid has disclosed the differences in the behavior of each of the two H-bonds and the contribution of each bond to the mechanism of polyimide formation from the respective H-complexes.For part 5, see ref.¹ Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 300–303, February, 1993.     

Structure–property correlations of sulfonated polyimides. II. Effect of substituent groups on membrane properties

A series of sulfonated polyimides with increasing alkyl substituents in the o‐position to diamine were synthesized from 4,4′‐methylene dianiline, 4,4′‐diamine‐3,3′‐dimethyl‐diphenylmethane, and 4,4′‐diamine‐3,5,3′,5′‐tetraethyl‐diphenylmethane using 1,4,5,8‐naphthalenetetracarboxylic dianhydride and perylenetetracarboxylic dianhydride by chemical imidization method. 4,4′‐Diaminobiphenyl 2,2′‐disulfonic acid was used as sulfonated diamine. The variation in the membrane properties with increase in substitution was analyzed. Solubility increased with substitution whereas the thermal stability decreased with increase in substitution. Ion exchange capacity and water uptake reduced with increase in substitution because of the low sulfonic acid content at a particular weight due to the increased molecular weight of the repeating unit. The conductivity of the substituted diamines was higher than the unsubstituted diamines at higher temperature regardless of low ion exchange capacity and water uptake. The increase in conductivity with increase in temperature was more rapid in polyimides than in Nafion®115. Hydrolytic stability of the polyimides with substitution is more than the unsubstituted diamines. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3621–3630, 2004     

Preparation of ultrathin films of aromatic polymides by vapor deposition polymerization from N-silylated aromatic diamines or aromatic tetracarboxylic dithioanhydride

A novel method for the preparation of ultrathin films of aromatic polyimides was developed through vapor deposition polymerization from combinations of monomer pairs of either N,N′-bis (trimethylsilyl)-substituted aromatic diamines and pyromellitic dianhydride or aromatic diamines and pyromellitic dithioanhydride. Both diamine component and tetracarboxylic dianhydride component were evaporated simultaneously at a stoichiometric molar ratio under vacuum, giving a deposited film on a substrate, which consisted of a polyamic acid derivative formed by the ring-opening polyaddition. The deposit was then converted to polyimide by thermal imidization at a relatively lower temperature, compared with a conventional method using the parent diamine and tetracarboxylic dianhydride. The properties of polyimide ultrathin films such as thermal stability, chemical resistance, and dielectric behavior were almost the same as those of the polyimide films prepared by a conventional method.     

High temperature polymers. III. Diphenyl sulfone-based polyamide-imides

High temperature thermoplastic polyamide-imides were prepared from a new series of aromatic diamines containing the diphenylsulfone unit and alternatively, oxydiphenyl and diphenylisopropylidene units. The polymers were prepared in their completely imidized form by using a facile in situ chemical imidization reaction which offers several advantages over the conventional thermal imidization process. The sulfone-based polyamide-imides exhibited an excellent combination of moldability, thermal stability, mechanical properties and solvent resistance. Analysis of the properties of these polymers in terms of structural variations permits a useful correlation of the effect of various structural units on performance. The polar diphenyl sulfone and amide-imide units increase the glass transition temperature and improve solvent resistance while the oxydiphenyl and diphenylisopropylidene units improve thermoplasticity. Sulfone ether diamine polyamide-imide (VI) offers the best combination of high temperature performance and moldability.     

Synthesis of aromatic polyamide-imides from N,N′-bis(trimethylsilyl)-substituted aromatic diamines and 4-chloroformylphthalic anhydride

The polymerization of N,N′-bis(trimethylsilyl)-substituted aromatic diamines with 4-chloroformylphthalic anhydride in various solvents at a temperature range between 10 and 70°C afforded polyamide-amic acid trimethylsilyl esters having inherent viscosities of 0.8–1.4 dL/g. Transparent and flexible films of the silylated precursor polymers were obtained by casting directly from the polymer solutions. Desilylation of the silylated polymers with methanol resulted in the formation of the corresponding polyamide-amic acids. Subsequent thermal imidization of the silylated precursor polymers with the elimination of trimethylsilanol afforded yellow, transparent, and tough films of the aromatic polyamide-imides. The thermal conversion of the silylated precursor polymer to polyamide-imide proceeded almost as rapidly as that of the corresponding polyamide-amic acid prepared by a conventional method from the parent aromatic diamine and 4-chloroformylphthalic anhydride.     

Investigation of polyimide formation from the complexes of the diester of benzophenonetetracarboxylic acid with diamines 7. Role of theo-carboxylic group of acid diester in the formation and imidization of H-complexes

The kinetics of thermal imidization of various H-complexes of semiesters of bis(o-phthalic) acids with diamines was studied. The activation energy of the imidization was shown to increase with increasing pK_a value of the diamine andE _a value of the dianhydride and with decreasing nucleophilicity of the alcohol used for the synthesis of H-complexes. The experimental kinetic data and the results of quantum chemical calculations of the heats of formation of the initial H-complexes and transition states made it possible to propose a mechanism for the imidization reaction. This mechanism takes into account the catalytic effect of the carboxylic group of the semiester in theo-position with respect to the ester group.For report 6, seeIzv. Akad. Nauk, Ser. Khim., 1993, 300 [Russ. Chem. Bull., 1993,42, 255 (Engl. Transl.)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1060–1065, June, 1995.     

Synthesis of conformationally diverse tetrathiacalix[4]arene(amido)crowns and tetrathiacalix[4]arene amides with pendant amine functions

A series of conformationally diverse novel tetrathiacalix[4]arene(amido)crowns and amides from tetrakis((ethoxycarbonyl)methoxy)p-tert-butyl tetrathiacalix[4]arene and its debutylated analog have been prepared by their reaction with diamines [H₂N(CH₂)_nNH₂; n=2,3,4, and 6] and polyamines. It has been determined that the length of the alkyl spacer in diamines is pivotal for the formation of either the tetrathiacalix[4]arene bis(amido)crowns or tetrathiacalix[4]arene amides with pendant amine functions. The synthesized compounds represent potential building blocks for achieving sophisticated molecular assemblies for molecular organization and recognition. Single crystal X-ray analysis of tetrathiacalix[4]arene bis(amido)crown 6a revealed that it has a 1,3-alternate conformation, which forms supramolecular complexes with chloroform.     

Acid-catalyzed reactions in polyimide synthesis

Melts of aromatic carboxylic acids are found to be excellent reaction media for 1-pot high molecular weight polyimide synthesis from diamines and tetracarboxylic acid dianhydrides. No reversible reaction of polyamic acids (PAA) formation was observed. The effect of the reactivity equalization was observed for low- and high reactive diamines in acid media. The intrinsic acid catalysis of the imidization reaction was shown to take place also in polycyclization of PAA in concentrated solutions in amic solvents. It is found that the dependence of relative imidization rate (% conv./min) vs. AA/N-MP ratio for model low molecular and oligomeric amic acids (AA) in N-MP at 140–150°C possesses a sharp maximum near the molar ratio 1:1, the imidization rate at the point of the maximum being an order of magnitude higher than that for diluted solutions. A scheme is proposed which includes the opportunity of two reaction channels to occur: A usual one (I) and a catalytic one (II). In diluted solutions and in solid phase experiments with easy evacuation of volatile products, the role of catalytic channel II is low. To the contrary, in high concentrated solutions or in solid phase experiments under the conditions exluding volatile products evacuation, the catalytic channel becomes the key one. It is proposed that the catalytic reaction proceeds via the common acid catalysis mechanism, the solvent and water playing the role of co-catalysts, probably through the mechanism of ionic dissociation of AA or hydrogen- bound complex AA-solvent. It is shown that the water released in the course of solid phase imidization of phtalamic acid at 140°C under the conditions where vaporization is impossible causes a sharp autocatalytic effect after initial 20%-conversion period to obtain entirely imidizied product.     

Preparation and properties of novel polyimides derived from 4‐aryl‐2,6 bis(4‐amino phenyl)pyridine

To prepare novel polyimides with enhanced thermal stability and high solubility in common organic solvents, diamine monomers, 4‐aryl‐2,6 bis‐(4‐amino phenyl)pyridine, were introduced. The diamines were reacted with three different conventional aromatic dianhydrides including pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, and hexafluoroisopropylidene‐2,2‐bis(phthalic‐dianhydride) (6FDA) in dimethylacetamide solvent to obtain the corresponding polyimides via the polyamic acid precursors and chemical imidization. The monomers and polymers were characterized by Fourier transform infrared spectroscopy, ¹H NMR, mass spectroscopy, and elemental analysis; and the best condition of polymerization and imidization were obtained via the study of model compound. The polyimides showed little or no weight loss by thermogravimetric analysis up to 500 °C, and those derived from 6FDA exhibited good solubility in various polar solvents. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3826–3831, 2001     

Study of the formation of polyimide from complexes of benzophenonetetracarboxylic acid diester with different diamines. 2. Features of thermal imidization of the molecular complex of benzophenonetetracarboxylic acid diester with 2,6-diaminopyridine

H-bond complexes of benzophenonetetracarboxylic acid dimethyl ester with 2,6-diaminopyridine (BZPE·DAP) have a dimeric structure in which one of the amino groups of the diaminopyridine participates in the formation of an H bond and the other does not form strong intermolecular bonds. During thermal imidization, the relative reactivity of the free amino group is lower than the reactivity of the group bound in the complex. In the BZPE·DAP system, 10% of the free amino groups remain after completion of imidization and they disappear at a high temperature. It is hypothesized that they can participate in the formation of interchain imide bonds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 530–533, March, 1990.     

One-pot high-temperature synthesis of polyimides in molten benzoic acid: Kinetics of reactions modeling stages of polycondensation and cyclization

For aromatic and aliphatic diamines of significantly different basicities, the kinetics of acylation with phthalic anhydride in glacial acetic acid in the range 16–70°C and of imidization of corresponding bis(o-carboxyamides) in acetic acid at 140°C has been studied. The reactions under study model the stages of polycondensation and intramolecular cyclization, respectively, in the high-temperature catalytic synthesis of polyimides in molten benzoic acid. It has been established that the acylation of amino groups in acetic acid proceeds as a reversible reaction and is catalyzed by the acidic medium. The kinetic and thermodynamic parameters of the above-mentioned model reactions have been determined, and the effect of the chemical structure of diamines on these parameters has been assessed. On the basis of the experimental data obtained for the model reactions, it is inferred that, in the synthesis of polyimides in benzoic acid, the overall rate of the process is determined by the rate of the intramolecular cyclization. A low sensitivity of the cyclization reaction to a change in the structure of the starting diamines explains why high-molecular-mass polyimides can be prepared at comparable rates under these conditions from both high-and low-basicity diamines.     

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     

Kinetic investigations of formation of polyimides containing arylene sulfone ether linkages by potentiometric titration and their characterization

In this work, thermal solution imidization kinetics of two high performance polyimides, prepared from the polycondensation of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) with 4,4′-bis(3-aminophenoxy)diphenylsulfone (DAPDS) were investigated using nonaqueous titration technique with tetramethylammonium hydroxide. Most of the kinetic investigations, found in the literature, are based on the aromatic p-diamines.^1,2 In the present work, attention was focused on imidization kinetics with m-substituted aromatic diamines having electron donating ( O ) and electron withdrawing ( SO₂ ) groups in the same molecule. Kinetic parameters, namely the rate constants, activation energies, entropies and enthalpies of imidization reactions were determined and compared with the literature values. It is reported in literature³ that electron affinities of dianhydrides and ionization potentials of diamines, have strong influence on the reaction rate and activation energies of imidization. Activation energy (E_a) values were found to be 66 and 57 kJ/mol for DAPDS/PMDA and DAPDS/BTDA respectively, and order of reaction was found to be second order. Polyimides DAPDS/PMDA and DAPDS/BTDA, subjected to kinetic investigation, showed glass transition temperatures of 267°C and 241°C, both were found to be thermally stable up to 500°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2981–2990, 1997     

Non‐isocyanate strategy for anionically stabilized water‐borne polyurea dispersions and coatings

An isocyanate‐free strategy for the preparation of anionically stabilized water‐borne polyurea (PU) dispersions was developed with diamines, dicarbamates, and dianhydrides as monomers. Poly(amic acid urea)s (PAAUs) with number average molecular weights up to 34 kDa were synthesized from ethylenediaminetetraacetic dianhydride and diamine‐functional PUs. The latter were produced from polymerization of dicarbamates and diamines. The factors that affected the particle sizes of the corresponding PAAU dispersions were investigated. Water‐borne PAAU coatings cured at elevated temperatures exhibited much better material properties than those cured at 50 °C as a result of crosslinking due to amine/carboxylic acid reactions and noncyclic imidization. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1078–1090     

Synthesis and properties of poly(amic acid)s and polyimides based on 2,2′,6,6′‐biphenyltetracarboxylic dianhydride

Poly(amic acid)s (PAAs) having the high solution stability and transmittance at 365 nm for photosensitive polyimides have been developed. PAAs with a twisted conformation in the main chains were prepared from 2,2′,6,6′‐biphenyltetracarboxylic dianhydride (2,2′,6,6′‐BPDA) and aromatic diamines. Imidization of PAAs was achieved by chemical treatment using trifluoroacetic anhydride. Among them, the PAA derived from 2,2′,6,6′‐BPDA and 4,4′‐(1,3‐phenylenedioxy)dianiline was converted to the polyimide by thermal treatment. The heating at 300 °C under nitrogen did not complete thermal imidization of PAAs having glass‐transition temperatures (T_g)s higher than 300 °C to the corresponding PIs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6385–6393, 2006     

Structure‐property relationships for a series of amorphous partially aliphatic polyimides

High molecular weight, soluble, amorphous, partially aliphatic polyimides were successfully synthesized using an ester acid high‐temperature solution imidization route, which allows one to control desired glass‐transition (T_g) and processing temperatures. This method involves the prereaction of aromatic dianhydrides with ethanol and a tertiary amine catalyst to form ester acids, followed by the addition of diamines. Subsequent thermal reaction forms fully cyclized polyimides. This reaction pathway eliminates the need for anhydrous solvents and overcomes the problem of salt formation commonly observed for nucleophilic, more‐basic aliphatic amines when utilizing the traditional polyamic acid synthesis route. The molar ratio of aromatic‐to‐aliphatic diamines was varied to generate a series of copolyimides with the chosen dianhydride and tailor the physical properties for specific adhesive applications. This series of copolyimides was characterized by their molecular weight, T_g, thermal stability, coefficient of thermal expansion, refractive index, and dielectric constant. Structure‐property relationships were established. The γ and β sub‐T_g viscoelastic properties were researched to understand their molecular origins. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1503–1512, 2002     

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.     

Synthesis of Bis(Amido Sulfimides) from 2-Sulfoterephthalic Acid Imide Chloride

A series of bis(amido sulfimides) were prepared by condensation of 2-sulfoterephthalic acid imidechloride with aliphatic, aromatic diamines.