Synthesis and characterization of new polyimides containing ethynylene linkages

We have synthesized a series of new diamines containing bis(ethynylaniline) linkages by bromine substitution reaction of ethynylaniline with 4,4′-bis(4-bromophthalimido)diphenylether (PODA) or 1,4-bis(4-bromophthalimido)benzene (PPDA). The intermediates were separated at each step, purified and characterized by the spectroscopic techniques. The model compound having imide and triple bond moiety was synthesized in order to elucidate the nature of the products formed from the ethynyl curing by FT-IR spectroscopy. The polymerization reaction of ethynylaniline diamines with various dianhydrides gave fully imidized and soluble aromatic polyimides. The thermally cured polyimide samples displayed good solvent resistance. The thermal crosslinking of triple bond moieties in the main chain was carried out by heating in the temperature range from 150 to 400 °C. The glass transition temperature of polyimide completely disappeared after heat treatment at 400 °C for 5 min. The polyimides derived from diamines containing bis(ethynylaniline) groups were thermally stable after heat treatment.     

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.     

A new synthetic route of 4,4′-hexafluoroisopropylidene-2,2-bis-(phthalic acid anhydride) and characterization of 4,4′-hexafluoroisopropylidene-2,2-bis-(phthalic acid anhydride)-containing polyimides

The title product 4,4′-hexafluoroisopropylidene-2,2-bis-(phthalic acid anhydride) was prepared from hexafluoroacetone and o-xylene as the starting materials by condensation, oxidation and dehydration three-step reaction sequence. It reacted with diamines in DMF or xylene to give polyimides by condensation polymerization. Thermal and viscosity analyses show that these polyimides have lower molecular weight but excellent thermal stability.     

Synthesis and polymerization mechanism of bisacetoacetamides

Bisacetoacetamides were prepared, and their polymerization was investigated. The acetoacetyl groups were introduced to diamines by the reaction with diketene to give bisacetoacetamides. They were polymerized under high pressure (34.5 MPa) at 200 °C for 30 min to create the crosslinked films. The polymerization mechanism was studied by a model reaction of acetoacetanilide. The model‐reaction results indicated that the polymerization of bisacetoacetamides proceeded by addition reactions of the isocyanates formed as intermediates and in part by condensation reactions between the acetoacetamido groups. The isocyanates also reacted with the urea groups on the polymer chains to form biurets, which would cause crosslinking. In the presence of a diamine, the reaction produced a soluble oligourea. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1456–1462, 2001     

可溶性聚酰亚胺液晶取向膜的制备与性能

液晶取向膜是液晶显示器中的关键材料,为了制得性能优良的液晶取向膜,我们通过铃木偶联反应制备了3种含有不同末端基团的3,5-二氨基联苯,将制得的3种二胺单体分别与环丁烷四甲酸二酐聚合得到3种新型的聚酰亚胺。 利用核磁氢谱对单体和聚合物的结构进行了表征,测试了聚合物的溶解性、热稳定性以及用作液晶取向膜的性能。 结果表明,所得的聚酰亚胺具有良好的溶解性和热稳定性,经过机械摩擦后,末端带有甲氧基的聚酰亚胺能使液晶分子平行于摩擦方向取向,末端带有苯氧羰基和联苯氧羰基的聚酰亚胺能使液晶分子垂直于摩擦方向取向。 此类可溶性的聚酰亚胺液晶取向膜将简化制备工艺并在柔性显示器件中具有较大的应用价值。     

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.     

Soluble polyimides containing alicyclic structures

A series of novel aromatic diamines containing kinked cycloalkane structures between two phenyl rings were synthesized by HCl-catalyzed condensation reaction of excess aniline and corresponding cycloalkanone derivatives. The structures of the diamines were indentified by ¹H NMR, ¹³C NMR, FT-IR spectroscopy and elemental analysis. The polyimides were synthesized from the obtained diamines with various aromatic dianhydrides by one-step polymerization in m-cresol. The polymerization was conducted for 6∼8 h with refluxing, which was enough to obtain the polymers with high molecular weight. The inherent viscosities of the resulting polyimides were in the range of 0.37∼1.66 dl/g. All polymers were readily soluble in common organic solvents such as chloroform, tetrachloroethane, dimethylacetamide, etc. and the glass transition temperatures were observed at 290 to 372°C. UV-visible spectra were obtained to measure the transparency of polymer films. Most of the polymers showed high transmission above 90 % in the wavelength of 450 ∼ 600 nm.     

Preparation and properties of processable polyimides having bulky pendent ether groups

A series of aromatic diamines containing pendent methoxy, phenoxy, and biphenoxy moieties were synthesized. By the reaction of diamines with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), several kinds of polyimides having bulky pendent ether groups were synthesized. Thermal properties and processability such as melt processability and solubility in organic solvents of obtained polyimides were investigated by focusing on the chemical structures of their repeating structure units. It was found that the thermal stability and melt processability of the polyimides did not strongly depend on the existence of bulky pendent phenoxy and biphenoxy moieties. Their solubility in organic solvents, however, was improved by introducing the bulky pendent ether groups such as methoxy, phenoxy, and biphenoxy moieties into their repeating structure units. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 971–978, 1998     

Preparation and properties of polyamides and polyimides containing phenoxathiin units

Novel polyimides and polyimides having phenoxathiin units have been prepared. Polyamides with inherent viscosities in the range of 0.5–2.9 were readily prepared by the polycondensations of phenoxathiin diamines with aromatic diacyl chlorides and of aromatic diamines with new phenoxathiin diacyl chlorides. The polyimides were synthesized from phenoxathiin diamines and pyromellitic dianhydride by using a two-step procedure. The polyamic acids which formed in the first step had inherent viscosities ranging from 1.0 to 1.6, and they were converted to the polyimides by thermal cyclodehydration. Some of the phenoxanthiin-containing polyamides were highly soluble in polar amide solvents and dimethyl sulfoxide. A series of novel polymers containing phenoxathiin units were much more thermostable than the corresponding polymers having open-chain diphenyl ether linkages.     

Synthesis and characterization of soluble polyimides from 2,2-bis(4-aminophenyl)cycloalkane derivatives

New aromatic diamines [(1) and (2)] containing polycycloalkane structures between two benzene rings were synthesized by HCl-catalyzed condensation reaction of aniline hydrochloride and corresponding polycycloalkanone derivatives. The structures of diamines were identified by ¹H-NMR, ¹³C-NMR, FTIR spectroscopy, and elemental analysis. The polyimides were synthesized from the obtained diamines with various aromatic dianhydrides by one-step polymerization in m-cresol. The inherent viscosities of the resulting polyimides were in the range of 0.34–1.02 dL/g. The polyimides showed good thermal stabilities and solubility. All the polymers were readily soluble in N-methyl-2-pyrrolidone, m-cresol, tetrachloroethane, etc. Some of them were soluble even in chloroform at room temperature. The glass transition temperatures were observed in the range of 323–363°C, and all of the polymers were stable up to 400°C under nitrogen atmosphere. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3449–3454, 1999     

Polyimides containing carbonyl and ether connecting groups. III

Several new polyimides were prepared from the reaction of three aromatic dianhydrides with two new methyl substituted aromatic diamines containing carbonyl and ether connecting groups between the aromatic rings. The diamines were prepared from the reactions of 3-methyl-4-aminophenol and 3,5-dimethyl-4-aminophenol with 1,3-bis(4-fluorobenzoyl) benzene in the presence of potassium carbonate. The 300°C cured polyimides containing methyl substituents were shown to be armorphous by wide angle X-ray diffraction and exhibited glass transition temperatures between 231–281°C. The properties of these new polyimides containing methyl substituents were compared with polymides of the same chemical structure but without methyl substituents.     

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     

Synthesis and characterization of polyimides based on novel isomeric perfluorinated naphthylenediamines

Novel highly fluorinated polyimides containing hexafluoronaphthylene fragment in the main chain were prepared by the two-stage polymerization of 2,7- and 2,6-diaminohexafluoronaphthalenes with 4,4′-oxydiphthalic anhydride: polycondensation in a solution at 80 °C followed by high-temperature solid-state chain extension. The influence of hexafluoronaphthylene fragment isomerism on the key polyimide features - molecular weight, thermal stability, solubility, optical properties - was characterized. Polyimides based on 2,7-diaminohexafluoronaphthalene or easily accessible mixture of isomeric diamines formed the flexible, transparent, and thermostable films.     

Heat-resistant polymers containing bipyridyl units. III. Polyimides having o-, m-, or p-phenylenedioxy linkage

New series of diamines having pyridine rings and o-, m-, or p-phenylenedioxy linkages were prepared by condensation of chloronitropyridine with isomeric dihydroxybenzenes followed by chemical reduction. The polymerization of the diamines with benzo-phenonetetracarboxylic acid dianhydride gave polyamic acids with the inherent viscosities in the range 0.21 to 1.30 dl/g. The conversion of these polyamic acids to polyimides was carried out thermally and the resulting polyimides exhibited very good solubility in organic solvents.     

Thermal conversion of hydroxy-containing polyimides to polybenzoxazoles. Does this reaction really occur?

Hydroxy-containing polyimides with a low level of structural defects have been produced by the reaction of aromatic tetra-carboxylic acids with hydroxy containing aromatic diamines in water, as this method avoids the normal ester impurities formed by the standard polyimide synthesis techniques using tetra-carboxylic dianhydrides in dry polar solvents. Detailed FTIR studies focused on the controlled thermolysis of these purified alpha-hydroxypolyimides and their model compounds has revealed that the hydroxy groups are lost at significantly lower temperatures and times than the imide groups. This observation does not support previous literature reports which suggested that benzoxazole formation occurs and has implications for the style of materials ultimately produced. We propose a new mechanism and provide evidence to indicate that the polymers initially produced by the thermolysis reaction of alpha-hydroxypolyimides are actually crosslinked, imide containing biphenylene derivatives.     

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 evaluation of polyimides derived from spirobisindane dietheranhydride

Polyimides derived from 5,5′-[(2,2′,3,3′-tetrahydro-3,3,3′,3′-tetramethyl-1,1′-spirobi[1H-indene]-6,6′-diyl)bis(oxy)]bis-1,3-isobenzofurandione (spirobisindane dietheranhydride, SBIDA) and 20 plus aromatic diamines were prepared. The weight percentage of cyclic contaminants in each polyimide, estimated by gel permeation chromatography, ranges from 4 to 25%. The amount of cyclics formed in each polyimide depends on the distance and spatial orientation of the two amino groups on the aromatic diamines as well as the rigidity of the diamines. The formation of SBIDA-containing polyimide was found to be catalyzed by alkali metal ions even when the reaction was conducted in m-cresol. Thermal stability and glass transition temperature of those SBIDA-derived polyimides were examined with thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Two promising compositions were scaled up and their mechanical properties were obtained. © 1993 John Wiley & Sons, Inc.     

Designing aromatic polyamides and polyimides for gas separation membranes

Aromatic polyamides and polyimides with improved gas permselectivity, can be designed and prepared by systematically changing structural elements that affect these properties. Indeed, a conscientious choosing of the chemical changes may still provide a promising approach to get better and better polymers for selective filtration of gases. The results of this work, in which novel monomers have been used, have confirmed that gas permeability through aromatic polyamides and polyimides much higher than that of conventional polyamides and polyimides can be achieved. It has been done by introducing bulky side groups, using non-planar monomers, and combining these elements on both monomers: diamines and dianhydrides or diamines and diacids. A theoretical study has also been made to explain the behaviour of some individual polymers, comparing experimental and calculated values of density and free volume.     

Polyimides containing carbonyl and ether connecting groups

Geveral new polyimides were prepared from the reaction of four aromatic dianhydrides with four new diamines containing carbonyl and ether connecting groups between the aromatic rings. The diamines were prepared from the reaction of 4-aminophenol with activated aromatic difluoro compounds in the presence of potassium carbonate. Several of these polyimides were shown to be semicrystalline as evidenced by wide angle x-ray diffraction and differential scanning calorimetry. Glass transition temperatures ranged between 192 and 247°C and crystalline melt temperatures were observed between 350 and 442°C. The polyimide from the reaction of 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride and 1,3-bis(4-aminophenoxy-4′-benzoyl)benzene provided a semicrystalline solvent resistant transparent film with high tensile properties and compression molded compact tension specimens with high fracture toughness.     

Homogenous one-pot synthesis of polyimides in polyphosphoric acid

A one-pot synthetic method to produce aromatic polyimides with high molecular weights from corresponding diamines and dianhydrides was developed, in which polyphosphoric acid (PPA) played a role of an excellent media for one-step synthesis of completely cyclized polyimides. The polymerization was carried out in the solid content of 10 wt/v% at 220 °C. The resulting products exhibited a homogeneous solution in the non-volatilizable PPA instead of precipitation form of the polyimides. The content of P₂O₅ in PPA had an influence on the molecular weight of the products, and the high percentage of P₂O₅ resulted in the relative high inherent viscosity. FTIR and Carbon-13 NMR were employed to analyze the structures and TGA was used to evaluate the thermal stability. The polyimides prepared by this one-step route exhibited good thermal properties and high values of activation energies for the degradation, on comparison with the polyimides prepared in DAMc by two-step polymerization method.