Synthesis and characterization of novel aromatic poly(imide–benzoxazole) copolymers

New poly(imide–benzoxazole) copolymers were prepared directly from a dianhydride, a diacid chloride, and a bis(o‐diaminophenol) monomer in a two‐step method. In the first step, poly(amic acid–hydroxyamide) precursors were synthesized by low‐temperature solution polymerization in an organic solvent. Subsequently, the thermal cyclodehydration of the poly(amic acid–hydroxyamide) precursors at 350 °C produced the corresponding poly(imide–benzoxazole) copolymers. The inherent viscosities of the precursor polymers were around 0.19–0.33 dL/g. The cyclized poly(imide–benzoxazole) copolymers had glass‐transition temperatures in the range of 331–377 °C. The 5% weight loss temperatures ranged from 524 to 535 °C in nitrogen and from 500 to 514 °C in air. The poly(imide–benzoxazole) copolymers were amorphous, as evidenced by the wide‐angle X‐ray diffraction measurements. The structures of the precursor copolymers and the fully cyclized copolymers were characterized by Fourier transform infrared, ¹H NMR, and elemental analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6020–6027, 2005     

Preparation of dibenzofuran-type amorphous polyetherketone by novel etherification reaction

4-Fluorobenzophenone reacted with potassium carbonate in the presence of silica catalyst in diphenyl sulfone solvent to yield 4,4′-dibenzoyldiphenyl ether. This new etherification reaction was extended to three difluoro aromatic ketones. 4,4′-Bis(4-fluorobenzoyl)diphenyl ether ( I ) reacted with potassium carbonate to yield a crystalline poly(oxy-1,4-phenylene-carbonyl-1,4-phenylene) (PEK) and 4,4′-bis{4-[4-(4-fluorobenzoyl)phenoxy]benzoyl}benzene ( II ) gave a crystalline poly(oxy-1,4-phenylene-carbonyl-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene-oxy-1,4-phenylene-carbonyl-1,4-phenylene-carbonyl-1,4-phenylene)(PEKEKEKK). 2,8-Bis(4-fluorobenzoyl)dibenzofuran ( III ) or 2,8-bis(4-chlorobenzoyl)dibenzofuran ( IV ) reacted with potassium carbonate to yield a poly(oxy-1,4-phenylene-carbonyl-2,8-dibenzofuran-carbonyl-1,4-phenylene) (PEKBK). The PEKBK was a noval amorphous polymer with the glass transition temperature of 222°C and it showed excellent thermal stability [T. Tanabe and I. Fukawa, Jpn. Pat., Kokai 64–74223 (1989)]. Several amorphous dibenzofuran type polyetherketone copolymers were prepared by coplycondensation of III with 4,4′-difluorobenzophenone ( V ) or 1,4-bis(4-fluorobenzoyl)benzene ( VI ) [T. Tanabe and I. Fukawa, Jpn. Pat., Kokai 1153722 (1989)]. © 1992 John Wiley & Sons, Inc.     

Novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor

A novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor based on a poly(amic acid hydroxyamide) bearing phenolic hydroxyl groups and carboxylic acid groups, a diazonaphthoquinone (DNQ) photosensitive compound, and a solvent was developed. Poly(amic acid hydroxyamide) was prepared through the polymerization of 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane, trimellitic anhydride chloride, and 4,4′‐oxydibenzoyl chloride. Subsequently, the thermal cyclization of the poly(amic acid hydroxyamide) precursor at 350 °C produced the corresponding poly(imide benzoxazole). The inherent viscosity of the precursor polymer was 0.17 dL/g. The cyclized poly(imide benzoxazole) showed a high glass‐transition temperature of 372 °C and 5% weight loss temperatures of 535 °C in nitrogen and 509 °C in air. The structures of the precursor polymer and the fully cyclized polymer were characterized with Fourier transform infrared and ¹H NMR. The photosensitive polyimide precursor containing 25 wt % DNQ photoactive compound showed a sensitivity of 256 mJ/cm² and a contrast of 1.14 in a 3‐μm film with a 0.6 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 5 μm was obtained from this composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5990–5998, 2004     

Diphosphan-tetraphenylnickelacyclopentadien

Reaction of 1,2-bis(diorganophosphino)ethanenickel dibromide (I) with 1,2,3,4-tetraphenyl-1,4-dilithiumbutadiene (II) at ?30°C yields diphosphannickelacyclopentadiene (III) which at elevated temperatures isomerizes to diphosphanecyclobutadienenickel(0) (IV). The thermodynamic and kinetic parameters of the rearrangement were determined. The structural and conformational analyses of III were carried out by means of ¹³C NMR, ³¹P NMR and Raman spectroscopy. The reactions of III and IV with CH₃COOH, CO, RCCR and RNCNR have been axamined and the observed reactivities III ? IV are discussed.     

Polyimides containing nonaromatic nitrogen linkages

Two diamines, 2,5-bis (4-aminophenyl)-2,5-diazahexane and 1,4-bis (4-aminophenyl)-1,4-diazacyclohexane were chosen as components for polyimidizations because they have melting points that differ by nearly 200°C (66–67 and 229–230°C, respectively) and are relatives of p-nitro-N,N-dimethylaniline. The melting points of the model compounds (phthalic anhydride) do not differ by as much as those of the free amines [303–304 and 386°C (DSC), respectively]. Six polyimides were prepared by a two-step polycondensation of the diamines with pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl) ethylidene] bis-1,3-isobenzofurandione. DSC thermograms failed to indicate any distinct transitions up to 450°C, however, the polyimide prepared from 2,5-bis (4-aminophenyl)-2,5-diazahexane and pyromellitic dianhydride shows a slight break in its DSC curve at 233°C.     

Synthesis and properties of novel poly(N-oxyimide)s

Novel poly(N-oxyimide)s (PNOI) were synthesized by the room temperature polycondensation of N,N′-dihydroxypyromellitimide (I) with dichloro compounds in N,N-dimethylformamide (DMF) in the presence of triethylamine both as base as well as catalyst. The dichloro compounds used were 1,4-bis(chloromethyl)-2,5-dimethylbenzene (II), 1,5-bis(chloromethyl)-2,4-dimethylbenzene (III), 1,4-bis(chloromethyl)-2,5-dimethoxybenzene (IV) and 1,4-dichlorobut-2-yne (V). Polymer synthesis, characterization, and properties such as density, viscosity, solubility, crystallinity, and thermal stability were described. Two model compounds, viz. (i) MNOI-1 from N-hydroxyphthalimide and a dichloro compound (III), (ii) MNOI-2 from I and benzyl chloride were also synthesized to confirm the formation of polymers. The polymers thus obtained had high intrinsic viscosities in the range 1.09–1.18 dl/g. The thermal decomposition of the polymers started around 260°C with 20–25% decomposition and about 50% weight loss was observed at 400°C.     

Thermal behaviour of ethynyl and ethenyl terminated imide resins

A series of ethynyl and ethenyl end-capped imide resins were synthesised by the reaction of 9,9-bis(4-aminophenyl) fluorene (BAF) with pyromellitic dianhydride (PMDA)3/3′, 4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA)/2,2-bis(3,4-dicarboxy phenyl) hexafluoropropane dianhydride (6F) and 3-ethynyl aniline/maleic anhydride. Structural characterisation was done by infra red and elemental analysis. Thermal characterisation was done by differential scanning calorimetry and thermogravimetric analysis. The decomposition temperatures of cured resins were above 200°C in nitrogen atmosphere. Char yield at 800°C ranged from 59–65.5%.     

Thermal and photochemical oxidation of 2,6-dimethylphenyl phenyl ether: A model for poly(2,6-dimethyl-1,4-phenylene oxide)

The oxygenation of 2,6-dimethylphenyl phenyl ether (I) at 260°C has resulted in the formation of 4-methylxanthone (II), 2-hydroxy-3-methylbenzophenone(III), 2-phenoxy-3-methylbenzaldehyde (IV), 2-phenoxy-3-methylbenzoic acid (V), 2-phenoxy-3-methylbenzyl o-cresotinate (VI), 2-phenoxy-3-methylbenzyl alcohol (VII), and 2-phenoxy-3-methylbenzyl 2-phenoxy-3-methylbenzoate (VIII), The photochemical oxidation at 75° produced compounds II, III, IV, VII, and VIII. Oxidation of poly(2,6-dimethyl 1,4-phenylene oxide) film at 200°C and photochemically at 50°C produced a carbonyl band at ca. 1730 cm^?1. The gel content of the photochemically aged film could be significantly reduced and the 1730 cm^?1 peak in the thermally aged specimen could be moved to longer wavelength by base treatment. The isolation of compound VIII in both processes with the model compound and the results with the polymer allows us to propose an ester group as a crosslinking unit in thermally and photochemically aged polymer film.     

New Coordination Polymers of 1,4-Bis(2″-Hydroxyphenylazomethine) Phenylene

Coordination polymers of 1,4-bis(2′-hydroxyphenylazomethine) phenylene have been prepared with the metal ions Ti(III), Cr(III), Fe(III), Mn(II), Ni(II), and Cu(II). They were characterized by elemental analysis, IR, and electronic spectra. The metal contents in all polymers were found to be consistent with a 1:1 (metal:ligand) stoichiometry. The thermal behavior of these coordination polymers has been studied by thermogravimetric analysis in air up to 750°C, and the data showed that they are thermally stable up to 200°C. Physical properties such as the solubility and viscosity of the polymer complexes were also determined. Electrical conductivity measurements of the synthesized polychelated polymers showed that they are insulators except for the Ni(II) complex which shows a semiconducting character. Mössbauer data clearly establish the 3 + oxidation state for the iron complex polymer.     

Phenylated polyquinoxalines from bis(phenylglyoxaloyl)benzene

Phenyl-substituted polyquinoxalines of unusually high oxidative-thermal stability were prepared by one-step solution condensations of aromatic tetraamines with 1,4-bis-(phenylglyoxaloyl)benzene and 1,3-bis(phenylglyoxaloyl)benzene. The final polymers thus obtained show exceptionally good solubility in a variety of common organic solvents, such as chloroform, tetrachloroethane, dichlorobenzenes, and certain phenols. Polymerizations in these solvents lead to polyquinoxalines of high molecular weight at reaction rates which depend upon the solvent used. The phenylated polyquinoxalines exhibited glass transition temperatures between 253 and 317°C and polymer decomposition temperatures between 515 and 540°C, depending upon structure. Isothermal decomposition at 400°C in air showed a strong dependency of weight loss on structure. Tough, flexible films were cast from solutions.     

Studies on heat-resistant poly(metal phthalocyanine)-imide copolymers

Several new poly(metal phthalocyanine)imide copolymers have been prepared using 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BPTDA), metal(11) 4,4′,4″,4″′-phthalocyanine tetraamines (MPTA), p-phenylenediamine, 4,4′-methylenedianiline, and 9,9-bis(4-aminophenyl)-fluorene (BAF). The attractive feature of these polymers is their high thermooxidative and thermal stability. The polymer decomposition temperatures of all the imide copolymers are greater than 500°C in air and N atomspheres. Another noteworthy property is their high char yield: 60–78% at 800°C in a N₂ atmosphere. Variation of the metal phthalocyanine concentration has a remarkable effect on the thermal stability and degree of polymerization. The most preferred molar proportion of the reagents MPTA, diamine, and BTDA is 1.25:7.5:10. These polymers may be useful in the preparation of heat-resistant films and fibers.     

Synthesis and properties of urethane-modified polyimides

The synthesis and properties of thermoplastic urethane-modified polyimides, based on different isocyanates, with different concentrations of hard segments and different ratios of imide and urethane groups, were studied. The effect of catalysts, isocyanates, and temperature was investigated on model reactions leading to formation of monoimides, bisimides, and polyimides. A polymer based on 2,4-TDI, poly(oxytetramethylene) glycol of 1000 molecular weight and pyromellitic dianhydride, with 75% of imide in the hard segments, retained about 50% of the original tensile strength at 120°C and about 30% at 150°C. Increasing the temperature up to 150°C had very little effect on the elongation of this copolymer. In general, increasing the imide concentration in the polymer structure provided better retention of stress-strain properties at elevated temperatures.     

Synthesis and characterization of new type soluble poly(amide–imide)s based on 6FDA imide modified polyterephthalamides

A series of new poly(amide–imide)s (PAIs, series III ) with good processability and characteristics was synthesized by utilizing organosoluble polyimide (PI, 6FDA–PI series) to improve poor‐solubility polyamide (PA, PTPA series), which used terephthalic acid (TPA) as a monomer. The III series PAIs were synthesized starting from the 2 : 1 molar ratio of aromatic diamines ( I ) and 6FDA to prepare imide ring‐preformed diamines ( II ) and then reacted with equimolar amount of TPA by direct polycondensation. Furthermore, by adjustment of the stoichiometry of the I , II, and TPA monomers, PAIs IV having various components were prepared. Most of the resulting PAIs having inherent viscosities between 0.70 and 1.74 dL/g were obtained in quantitative yields, and they were readily soluble in polar solvents such as N,N‐dimethylacetamide, N‐methyl‐2‐pyrrolidone, dimethylformamide, and dimethyl sulfoxide. All of the soluble PAIs afforded transparent, flexible, and tough films. The glass‐transition temperatures of PAIs III were in the range of 236–256 °C, and the 10% weight loss temperatures were recorded at 522–553 °C in nitrogen. The char yields of the III series polymers in nitrogen atmosphere were all higher than 56% even at 800 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 93–104, 2001     

Aromatic amino-claisen rearrangement in the synthesis of ellipticine

A convenient route is described for the preparation of 1,4-dimethylcarbazole — the key compound in the synthesis of the antitumoral alkaloid ellipticine. The interaction of 2,5-xylidine with 3-chlorocyclohexene led to N-(cyclohex-2-enyl)-2,5-xylidine (I), the two-hour heating of which at 140–150°C gave the product of an amino-Claisen rearrangement, 6-(cyclohex-2-enyl)-2,5-xylidine (II) with a yield of 82%. The intramolecular cyclization of compound (II) in polyphosphoric acid (130–140°C, 5 h) led to 5,6,7,8,12,13-hexahydro-1,4-dimethylcarbazole (III) in a yield of 75%. The dehydrogenation of substance (III) by boiling in trimethylbenzene in the presence of Pd/C gave 1,4-dimethylcarbazole (IV) with a yield of 87%. The conditions for performing the reactions and the physicochemical constants of the compounds obtained are given.     

Synthesis and Properties of Pyrrones Containing p-Benzoquinone Units

Novel pyrrones were synthesized by one-stage polycondensation in polyphosphoric acid of 2,3,5,6-tetraamino-l,4-benzoquinone with pyromellitic anhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, or 3,4,9,10-perylenetetracarboxylic dianhydride. The prepared polymers showed a considerable percentage of imide linkages, so they were heated at 350°C under high vacuum to increase the ring closure to the pyrrone structure. The polymers were insoluble in all common polar aprotic solvents, even in dimethylacetamide-water mixture, after reduction with sodium dithionite, but were slightly soluble in concentrated sulfuric and methanesulfonic acid. The thermal decomposition of the polymers (weight loss 5%) started above 400°C both under nitrogen and in air.     

The synthesis and thermal curing parameters of a novel quinoxaline monomer with terminal ethynyl thermoset and phenylethynyl intramolecular cycloaddition postcure capability

The Synthesis of 3,3′-bis(4-[3-ethynylphenoxy]phenyl)-7,7′-bis(phenylethynyl)-2,2′-diphenyl-6,6′-biquinoxaline (I) was accomplished by the reaction of 2,2′-bis(phenylethynyl)-5,5′-diaminobenzidine (II) and 4-(3-ethynylphenoxy)benzil. Thermal analysis of I indicated a softening temperature of 107°C, followed by an exotherm above 150°C that corresponded to a independent crosslinking reaction of the terminal acetylene groups and an intramolecular cycloaddition (IMC) reaction of the 2,2′-bis(phenylethynyl)biphenyl moieties. In the synthetic work substantial improvements were made in the synthesis of II. The sample of I was cured at 200°C and the maximum partially cured transition temperature attained was 280°C. A sample of 3,3′-bis(4,[3-ethynylphenoxy]phenyl)-2,2′-diphenyl-6,6′-biquinoxaline (IV) was similarly tested as a model without IMC capability and its corresponding value was 250°C. The difference between these two values is discussed briefly.     

Fluorinated poly(benzoxazole–imide)s

New poly(benzoxazole–imide)s have been prepared by polycondensation of bis(o-aminophenol)s, such as 3,3′ dihydroxybenzidine or 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane, with diacid chlorides containing both imide and hexafluoroisopropylidene groups. The soluble polymer precursor resulting from the first step of polycondensation in N-methylpyrrolidinone (NMP) at low temperature was processed into thin flexible films, which were then thermally treated to reach the fully cyclized structure of poly(benzoxazole–imide)s, as observed by infrared spectra. An alternative way to produce the cyclization was by heating at reflux the solution of polymer precursor in NMP. Thermal stability, glass transition temperature, dielectric constant and its dependence on relative humidity have been studied and compared with those of related polybenzoxazoles and other heterocyclic Polymers.     

Structure,thermal stability and decomposition of bis-allyl-zinc compounds

The structure, thermal stability and decomposition of solutions of diallylzinc (I), bis(2-methylallyl)zinc (II), bis(3-methylallyl)zinc (III) and bis(3,3-dimethylallyl)zinc (IV) in deuterated solvents, have been investigated by¹H NMR and by kinetic measurements at temperatures between ?125 and +180°C. At room temperature I, II, III and IV are dynamic systems and are best described as being rapidly equilibrating mixtures of all isomeric σ-allyl forms; the NMR spectra are averages weighted according to the relative concentrations of the respective forms. I displays a¹H NMR spectrum of a static σ-allyl system only below ?125°C and II only below ?115°C. At temperatures above 100°C the thermal decomposition of I–IV results in coupling of the allyl groups, decomposition via radicals being the major process. The coupled products exhibit CIDNP, in which the multiplet polarisations confirm a decomposition via randomly diffusing allyl radicals. In the allyl radicals CH₂CR¹CR²R³ an alternating spin density was proved experimentally. The thermal stability decreases in the order I > II > III > IV.     

New processable polyaromatic ether-keto-sulfones curable by intramolecular cyclization. XV

New processable polyaromatic ether-keto-sulfones were prepared from 2,2′-diiododiphenyl-4,4′-dicarbonyl dichloride (I), bis(p-phenoxybenzene)sulfone (II), isophthaloyl chloride (III), and diphenyl ether (IV) in Friedel–Crafts-type polymerizations. In the most promising of the iodine-containing polymers phenylacetylenyl groups were introduced in place of iodine. This polymer, with an initial monomer ratio of I:II:III:IV = 1:5:7:3, was further investigated. It is soluble in DMF, DMA, pyridine, and sulfuric acid. After curing it was insoluble in all solvents used and lost only 1.1% of its weight at 300°C when heated in air for three days. Hence in this cured state it has excellent chemical and thermal resistance. It can be cast into a film from solution in DMAc and a glass fiber laminate is readily prepared. The film is tough, transparent, and brown in color. The cured film is tougher than the uncured. The glass fiber laminate is also tough and fairly flexible. A distinct advantage of this type of polymer is its ready availability in relatively cheap raw materials. The phenylacetylenyl-group-containing polymer showed a transition temperature at 175°C and two exotherm peaks at 243 and 361°C which disappeared after curing in a DSC thermogram. Before and after curing this polymer displayed softening temperatures at 149 and 171°C, respectively, measured by a Vicat apparatus at a heating rate of 1°C/min. No melting temperatures up to 500°C were observed for any of the polymers in this study.     

Soluble imide–quinoxaline copolymers

Eight new phenylated imide–quinoxaline ordered copolymers were prepared. The synthesis consisted of one-step solution condensations of aromatic bis(o-diamines) with N,N′-bis(benzilyl)benzophenoneimide and N,N′-bis(benzilyl)tetrahydrofuranimide respectively. The polymers were all of high molecular weight and were soluble in a number of different solvents. Thermal gravimetric analysis showed that the aromatic benzophenoneimide-quinoxalines (decomposing between 490 and 530°C) were considerably more stable than the aliphatic tetrahydrofuranimide–quinoxalines (decomposing between 290 and 320°C). All polymers gave tough films which could be cast from solution.