Solution polymerization of polybenzimidazole

Polybenzimidazoles (PBI) are an important class of heterocyclic polymers that exhibit high thermal and oxidative stabilities. The two dominant polymerization methods used for the synthesis of PBI are the melt/solid polymerization route and solution polymerization using polyphosphoric acid as the solvent. Both methods have been widely used to produce high‐molecular weight PBI, but also highlight the obvious absence of a practical organic solution‐based method of polymerization. This current work explores the synthesis of high‐molecular weight meta‐PBI in N,N‐dimethyl acetamide (DMAc). Initially, model compound studies examined the reactivity of small molecules with various chemical functionalities that could be used to produce 2‐phenyl‐benzimidazole in high yield with minimal side reactions. ¹H NMR and FTIR studies indicated that benzimidazoles could be efficiently synthesized in DMAc by reaction of an o‐diamine and the bisulfite adduct of an aromatic aldehyde. Polymerizations were conducted at various polymer concentrations (2‐26 wt % polymer) using difunctional monomers to optimize reaction conditions in DMAc which resulted in the preparation of high‐molecular weight m‐PBI (inherent viscosities up to 1.3 dL g^?1). TGA and DSC confirmed that m‐PBI produced via this route has comparable properties to that of commercial m‐PBI. This method is advantageous in that it not only allows for high‐polymer concentrations of m‐PBI to be synthesized directly and efficiently, but can be applied to the synthesis of many PBI derivatives. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1795–1802     

Silicon-containing Schiff base and benzimidazole derivatives

Investigations were undertaken to obtain information for use in the development of new heat-stable polymers. Model silicon-containing Schiff base and benzimidazole derivatives were synthesized by reaction of p-(triphenylsilyl)-benzaldehyde with phenylenediamines. The structure and thermal stability of the products were studied. The reaction of p-(triphenylsilyl)benzaldehyde and o-phenylenediamine yielded N-p-(triphenylsilyl)benzylidene-o-phenylenediamine which readily oxidizes to form 2-p-(triphenylsilyl)phenylbenzimidazole. The di-Schiff bases, which most probably exist in trans-trans configurations, were obtained from reaction of the aldehyde derivative with m- and p-phenylenediamine. In contrast to similar Schiff bases without silicon, the products are soluble in organic solvents. The good resistance of the di-Schiff base and benzimidazole derivatives to thermal decomposition suggests that polymers with repeating units of such structures would also be heat-stable and might possess useful properties.     

Use of aromatic dialdehydes in the preparation of poly(p-benzoquinono)diimidazoles

Poly(p-benzoquinono)diimidazoles have been synthesized under mild conditions (100 or 150°C) by one-stage polycondensation in N,N-dimethylacetamide (DMAc) or in polyphosphoric acid of 2,3,5,6-tetraamino-p-benzoquinone (TABQ) with terephthalaldehyde and isophthalaldehyde. The model compound 2,6-diphenyl-1,5-dihydro-1′,4′-benzoquinono[2′,3′-d:5′,6′-d′]diimidazole was also prepared by condensation of TABQ with benzaldehyde in DMAc at 100°C. The prepared polymers were completely insoluble in organic solvents but slightly soluble (0.5%) in strong acids with viscosities (η_inh) in the range of 0.17–0.38 dL/g (c = 0.2% in formic acid). Their thermal stability was studied by TG analysis.     

Synthesis of 4-Aryl-1,5-benzodiazepine-2-carboxamides

4,N-Diaryl-1,5-benzodiazepine-2-carboxamides were synthesized by acid-catalyzed reaction of (Z)-4,N-diaryl-2-hydroxy-4-oxo-2-butenamides with o-phenylenediamine or N,N'-bis(triphenylphosphoranediyl)-o-phenylenediamine. The reaction mechanism is discussed.     

Synthesis and properties of Ortho-linked aromatic polyamides based on 4,4′-(2,3-naphthalenedioxy) dibenzoic acid

A novel aromatic dicarboxylic acid monomer, 4,4′-(2,3-naphthalenedioxy)-dibenzoic acid ( 3 ), was prepared by the fluorodisplacement reaction of p-fluorobenzonitrile with 2,3-dihydroxynaphthalene in N,N-dimethylformamide (DMF) in the presence of potassium carbonate followed by alkaline hydrolysis of the intermediate dinitrile. A series of novel aromatic polyamides containing ortho-linked aromatic units in the main chain were synthesized by the direct polycondensation of diacid 3 and a variety of aromatic diamines using triphenyl phosphite and pyridine as condensing agents in the N-methyl-2-pyrrolidone (NMP) solution containing dissolved calcium chloride. The resulting polyamides had inherent viscosities higher than 0.74 and up to 2.10 dL/g. All of these polyamides were soluble in polar solvents, such as NMP, DMF, N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide. Transparent, flexible, and tough films could be cast from their DMAc or NMP solutions. The solvent-cast films had high tensile strengths and moduli. Extensions to break were relatively low, except for the polymers derived from 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and 3,4′-oxydianiline, which had elongations of 82 and 62%, respectively. Except for the polyamide based on p-phenylenediamine, all the other polyamides were amorphous in nature. All the polymers are thermally stable to temperatures in excess of 450°C in either air or nitrogen atmosphere. The polymers exhibited glass transition temperatures ranging from 183 to 260°C and decomposition temperatures (10% weight loss) ranging from 462–523°C in air and 468–530°C in nitrogen. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3385–3391, 1997     

Naphtho[1′,2′:5,6]pyrano[2,3–6][1,5]benzodiazepine Derivatives

The reaction of 3-(dimethylamino)-1-oxo-1H-naphtho[2,1-b]pyran-2-carbaldehyde (Ia) with o-phenylenediamines or N-monosubstituted o-phenylenediamines in refluxing glacial acetic acid afforded the corresponding naphtho[1′,2′:5,6]pyrano[2,3-b][1,5]benzodiazepin-15-(8H)ones V in very good yields. A similar result was achieved when the reaction was carried out in refluxing pyridine, using N-monosubstituted o-phenylenediamine hydrochlorides. The isolation of a significant intermediate as well as the synthesis through a different univocal pathway confirmed the structure of the compounds V. Moreover the reaction of Ia with N-monosubstituted o-phenylenediamines in refluxing pyridine generally afforded only low yields of compounds V, sometimes together with naphtho[1′,2′:5,6]pyrano[2,3-b][1,5]benzodiazepin-15-(13H)ones VII, isomers of V.     

Preparation and properties of new aromatic polyamides from bis(4-aminophenyl) phenylphosphine and aromatic dicarboxylic acids

A new triphenylphosphine-type monomer, bis(4-aminophenyl) phenylphosphine, was synthesized starting from p-bromoaniline and dichlorophenylphosphine. The aromatic polyamides (aramids) containing triphenyphosphine unit in the polymer backbone was prepared by the polycondensation of this diamine with various aromatic diacid chlorides using a low-temperature solution method in N,N-dimethylacetamide (DMAc). The aramids having inherent viscosities of 0.4–0.7 dL/g were obtained in quantitative yields. The polymers were amorphous and soluble in various organic solvents such as DMAc, N-methylpyrrolidone, dimethyl sulfoxide, pyridine, and m-cresol. Transparent, tough, and flexible films were obtained by casting from the DMAc solutions. The glass transition temperatures of the aramids were in the range of 265–310°C, and the 10% weight loss temperatures were above 400°C in air. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of soluble aromatic polyurea-amides from new N,N′--dimethyl-N,N′-bis(aminophenyl)ureas and aromatic dicarboxylic acid chlorides

Aromatic polyurea-amides having inherent viscosities of 0.36–0.67 dL/g were synthesized by the low temperature solution polycondensation of new N,N′-dimethyl-N,N′-bis(aminophenyl)ureas with various aromatic dicarboxylic acid chlorides. All the polymers were amorphous, and most of them were soluble in a variety of organic solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide (DMAc), m-cresol, and pyridine. Some of the polymers could be cast from the DMAc solutions into transparent and flexible films having good tensile properties. The glass transition temperatures of the polyurea-amides obtained from the bis(4-aminophenyl)-substituted ureas were 244–272°C. The temperatures of 10% weight loss under nitrogen of the polymers were in the range of 430 and 480°C. © 1995 John Wiley & Sons, Inc.     

Synthesis and characterization of aromatic polyamides from 1,1-bis(4-aminophenyl)-2,2-diphenylethylene and aromatic diacid chlorides

Novel, soluble aromatic polyamides and copolyamides containing tetraphenylethylene units were prepared by the low temperature solution polycondensation of 1,1-bis(4-aminophenyl)-2,2-diphenylethylene and aromatic diamines with various aromatic diacid chlorides. Highmolecular-weight polyamides having inherent viscosities of 0.6–1.5 dL/g and number-average molecular weight above 21000 were obtained quantitatively. These polymers were readily soluble in various solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide and gave pale yellow, transparent, flexible films by casting from DMAc solution. The polymers had glass transition temperatures between 290 and 340°C, and started to lose weight around 400°C, with 10% weight loss being recorded at about 470°C in air.     

N-CYANOIMIDO-PHOSPHONYL/S-METHYL THIOCARBONATES: FACILE,USEFUL REAGENTS FOR THE SYNTHESES OF HETEROCYCLIC PHOSPHONATES

N-Cyanoimido-(O,O-dialkyl) phosphonyl/S-methyl thiocarbonates 2 were synthesized as facile, useful synthons for preparation of 1,3,5-triazine-, 1,2,4-triazole-, and 1,2,4-oxadiazole-phosphonates through cyclization reaction with various binucleophilic reagents. In addition, when 2a was treated with o-phenylenediamine, benzimidazole-2-yl phosphonate was obtained through addition–elimination reaction.     

Synthesis and Characterization of New Soluble Polyamides from 9,9-Bis[4-(chloroformylphenoxy)phenyl]xanthene and Various Aromatic Diamines

9,9‐Bis(4‐hydroxyphenyl)xanthene (BHPX) was synthesized in 82% yield from xanthenone in a one‐pot, two‐step synthetic procedure. A new diacyl chloride monomer, 9,9‐bis[4‐(chloroformylphenoxy)phenyl]xanthene (BCPX), was synthesized in three steps from the nucleophilic fluorodisplacement of 4‐fluorobenzonitrile with the dipotassium bisphenolate of BHPX, followed by alkaline hydrolysis of the intermediate bis(ether nitrile), and then chlorination with thionyl chloride. Several novel aromatic polyamides containing ether and bulky xanthene groups with the inherent viscosities (0.72–0.98 dL/g) were prepared by the low temperature polycondensation of BCPX with various aromatic diamines in N,N‐dimethylacetamide (DMAc) solution containing pyridine (Py). All new polyamides were amorphous and readily soluble in various polar solvents such as DMAc, N,N‐dimethylformamide (DMF), N‐methyl‐2‐pyrrolidone (NMP) and Py. These polymers showed relatively high glass transition temperatures between 236 and 298°C, decomposition temperatures at 10% weight loss ranging from 490 to 535°C and 483 to 515°C in nitrogen and air, respectively, and char yields at 700°C in nitrogen higher than 50%. Transparent, flexible, and tough films of these polymers cast from DMAc solutions exhibited tensile strengths ranging from 82 to 106 MPa, elongations at break from 10% to 25%, and initial moduli from 2.0 to 2.8 GPa.     

A novel class of organosoluble poly(arylene ether nitrile) copolymers containing methyl substituent and cardo xanthene moiety

9,9‐Bis(3‐methyl‐4‐hydroxyphenyl)xanthene (BMHPX) was synthesized in 72% yield by a HCl/ZnCl₂‐catalyzed condensation reaction of xanthenone with excess o‐cresol. Based on this new bisphenol monomer, a series of poly(arylene ether nitrile) (PAEN) and PAEN copolymers containing methyl substituent and cardo xanthene moiety were prepared by the nucleophilic substitution reaction of 2,6‐difluorobenzonitrile (DFBN) with BMHPX and with varying mole proportions of BMHPX to hydroquinone (HQ) (100/0–40/60) using N‐methyl‐2‐pyrrolidone (NMP) as solvent in the presence of anhydrous potassium carbonate. These polymers had inherent viscosities between 0.54 and 0.72 dl/g, and their weight‐average molecular weights and number‐average molecular weights were in the range of 32,600–36,400 and 17,300–18,300, respectively. All PAENs were amorphous and were soluble in dipolar aprotic solvents such as NMP and N,N‐dimethylacetamide (DMAc), and even in THF and chloroform at room temperature. The resulting polymers showed glass transition temperatures (T_g's) between 213–226°C, and the T_g values of the copolymers were found to increase with increase of the BMHPX units content in the polymer. Thermogravimetric studies showed that all the polymers were stable up to 404°C, with 10% weight loss temperatures ranging from 444 to 455°C, and char yields of 52–58% at 700°C in nitrogen. All new PAENs could be cast into transparent, strong, and flexible films with tensile strengths of 102–120 MPa, elongations at break of 14–18%, and tensile moduli of 3.3–3.7 GPa. Copyright © 2011 John Wiley & Sons, Ltd.     

New poly (amide-imide) syntheses. IX. Preparation and properties of poly(amide-imide)s derived from 2,7-bis (4-aminophenoxy) naphthalene and various bis (trimellitimide)s

Eleven bis(phenoxy) naphthalene-containing poly(amide-imide)s IIIa–k were synthesized by the direct polycondensation of 2,7-bis (4-aminophenoxy) naphthalene (DAPON) with various aromatic bis (trimellitimide)s IIa–k in N-methyl-2-pyrrolidone (NMP) using triphenyl phosphite and pyridine as condensing agents. Poly (amide-imide)s IIIa–k having inherent viscosities of 0.70–1.12 dL/g were obtained in quantitative yields. The polymers containing p-phenylene or bis(phenoxy) benzene units exhibited crystalline x-ray diffraction patterns. Most of the polymers were readily soluble in various solvents such as NMP, N, N-dimethylacetamide, dimethyl sulfoxide, m-cresol, o-chlorophenol, and pyridine, and gave transparent, and flexible films cast from DMAc solutions. Cast films showed obvious yield points in the stress-strain curves and had strength at break up to 87 MPa, elongation to break up to 11%, and initial modulus up to 2.10 GPa. These poly(amide-imide)s had glass transition temperatures in the range of 255–321°C, and the 10% weight loss temperatures were recorded in the range of 529–586°C in nitrogen. The properties of poly(amideimide)s IIIa–k were compared with those of the corresponding isomeric poly (amide-imide)s III′ prepared from 2,7-bis(4-trimellitimidophenoxy) naphthalene and aromatic diamines. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of organo-soluble poly(amide-imide)s based on 1,2-bis[4-(trimellitimido)phenoxy]ethane and aromatic diamines

<正>New organo-soluble poly(amide-imide)s(PAIs) 8a-8f were prepared from newly synthesized 1,2-bis[4,4'-(trimellitimido) phenoxy]ethane 6 via direct polycondensation with various aromatic diamines.The diacid 6 was synthesized by the condensation reaction of 12-bis[4-atninophenoxy]ethane 4 with trimellitic anhydride 5 in acetic acid.All polymers were obtained in quantitative high yields with inherent viscosities of 0.48-0.61 dL/g.All of these polymers were highly soluble in organic solvents such as,N-methyl-2-pyrrolidone(NMP),dimethylformamide(DMF),N,N'-dimethylacetamide (DMAc) and dimethylsulfoxide(DMSO) at room temperature and were fully characterized by means of NMR spectroscopy, FTIR spectroscopy,elemental analyses,inherent viscosity,solubility test,specific rotation,differential scanning calorimetry (DSC) and thermogravimetric analysis(TGA).     

Synthesis of benzylidene-pendant polyphthalimidines from flexible bisphthalides and various diamines

New polyphthalimidine-forming monomers, 5,5′-(oxydi-p-phenylenedicarbonyl)bis(3-benzylidenephthalide) and the 6,6′-derivative, were synthesized by the Friedel–Crafts reaction of diphenyl ether with 5- and 6-chloroformyl-3-benzylidenephthalide, respectively. The direct polycondensation of these bisphthalides with both aliphatic and aromatic diamines in o-phenylphenol at 200–250°C afforded polyphthalimidines having inherent viscosities of 0.2–1.2 dL/g in almost quantitative yields. Syntheses of aliphatic polyphthalimidines with higher inherent viscosities were also achieved by a two-step procedure involving ring-opening polyaddition and subsequent thermal cyclodehydration. All the polymers were amorphous and readily soluble in N-methyl-2-pyrrolidone (NMP), m-cresol, nitrobenzene, pyridine, and chloroform. Tough and flexible films could be cast from NMP solutions of the polymers. Glass transition temperatures of the polyphthalimidines were in the range of 158–246°C. The thermogravimetry of the aromatic polymers showed 10% weight loss in air and nitrogen at 445–515 and 500–520°C, respectively. The crosslinking reaction of some benzylidenependant polyphthalimidines took place at 300°C through double-bond addition to afford cured polymers with improved thermal stability.     

Syntheses and properties of aromatic polyamides and polyimides based on N-phenyl-3,3-bis[4-(p-aminophenoxy) phenyl] phthalimidine

N-Phenyl-3,3-Bis[4-(p-aminophenoxy)phenyl] phthalimidine ( II ) was used as a monomer with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to synthesize polyamides and polyimides, respectively. The diamine II was derived by a nucleophilic substitution of N-phenyl-3,3-bis(4-hydroxyphenyl) phthalimidine with p-chloronitrobenzene in the presence of K₂CO₃ and then hydro-reduced. Polyamides IV _a-g having inherent viscosities of 0.55–1.64 dL/g were prepared by the direct polycondensation of the diamine II with various aromatic diacids using triphenyl phosphite and pyridine as condensing agents. All the aromatic polyamides were amorphous and readily soluble in various polar solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide, dimethylsulfoxide, and N-methyl-2-pyrrolidone (NMP). Transparent and flexible films of these polymers could be cast from the DMAc solutions. These aromatic polyamides had glass transition temperatures in the range of 293–319°C and 10% weight loss occurred up to 480°C. The polyimides were synthesized from diamine II and various aromatic dianhydrides via the two-stage procedure that included ring-opening polyaddition in DMAc to give poly(amic acid)s, followed by thermal or chemical conversion to polyimides. Most of the aromatic polyimides obtained by chemical cyclization were found to be soluble in NMP, m-cresol, and o-chlorophenol. These polyimides showed almost no weight loss up to 500°C in air or nitrogen atmosphere. © 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of new soluble poly(amide‐imide)s derived from 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane

A series of new soluble poly(amide‐imide)s were prepared from the diimide‐dicarboxylic acid 2,2‐bis[4‐(4‐trimellitimidophenoxy)phenyl]hexafluoropropane with various diamines by direct polycondensation in N‐methyl‐2‐pyrrolidinone containing CaCl₂ with triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.52–0.86 dL · g^?1. The poly(amide‐imide)s showed an amorphous nature and were readily soluble in various solvents, such as N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide, pyridine, and cyclohexanone. Tough and flexible films were obtained through casting from DMAc solutions. These polymer films had tensile strengths of 71–107 MPa and a tensile modulus range of 1.6–2.7 GPa. The glass‐transition temperatures of the polymers were determined by a differential scanning calorimetry method, and they ranged from 242 to 279 °C. These polymers were fairly stable up to a temperature around or above 400 °C, and they lost 10% of their weight from 480 to 536 °C and 486 to 537 °C in nitrogen and air, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3498–3504, 2001     

Preparation and properties of aromatic polyamides from 1,4-bis(p-carboxyphenoxy)naphthyl and aromatic diamines

A new aromatic dicarboxylic acid, 1,4-bis (p-carboxyphenoxy)naphthyl ( 3 ), was synthesized by the reaction of p-fluorobenzonitrile with 1,4-naphthalenediol, followed by hydrolysis. Aromatic polyamides having inherent viscosities of 1.27–2.22 dL/g were prepared by the triphenyl phosphite activated polycondensation of diacid 3 with various aromatic diamines. Most of the resulting polymers showed an amorphous nature and were readily soluble in a variety of organic solvents including N,N-dimethyl-acetamide (DMAc), N-methyl-2-pyrrolidone (NMP), and m-cresol. Transparent, tough, and flexible films of these polymers could be cast from the DMAc or NMP solutions. The cast films had tensile strengths ranging from 64–104 MPa, elongations-at-break from 6 to 10%, and initial moduli from 1.52 to 2.14 GPa. These polyamides had glass transition temperatures in the range of 195 to 240°C. Almost all polymers were thermally stable up to 400°C, with 10% weight loss being recorded above 480°C in air and nitrogen atmospheres. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2273–2280, 1997     

Iron-Catalyzed Highly Efficient Aerobic Oxidative Synthesis of Benzimidazoles,Benzoxazoles, and Benzothiazoles Directly from Aromatic Primary Amines Under Solvent-Free Conditions in the Open Air

Solvent-free oxidative synthesis of benzimidazoles, benzoxazoles, and benzothiazoles from aromatic primary amines and o-phenylenediamine, o-aminophenol, and o-aminothiophenol has been achieved by using Fe(NO₃)₃ and TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxyl). This reaction can use air as an economical and green oxidant, and a wide variety of derivatives were obtained in good to excellent yields. The reaction mechanism was proposed and this method provides a direct, practical, and efficient approach for the preparation of substituted benzimidazoles, benzoxazoles, and benzothiazoles.     

Reactions of Methyl 4-Aminofurazan-3-carboximidate with Nitrogen-Containing Nucleophiles

Methyl 4-aminofurazan-3-carboximidate reacts with aromatic amines and hydrazines to give the corresponding amidines and amidrazones. The reaction of the title compound with o-phenylenediamine yields 3-amino-4-(2-benzimidazolyl)furazan, and with acylhydrazines N²-acyl-4-aminofurazan-3-carbohydrazides are formed. The latter undergo thermal intramolecular cyclization with formation of 3-amino-4-(1,2,4-triazol-3-yl)furazan derivatives containing various substituents in position 5 of the triazole ring.