Cyclopolycondensations. VI. Fully aromatic polybenzoxazinones from aromatic poly(amic acids)

New high temperature aromatic polybenzoxazinones of high molecular weight have been prepared by the cyclopolycondensation of 4,4′-diaminobiphenyl-3,3′-dicarboxylic acid (I) with aromatic dicarboxylic acid halides (II). The low temperature solution polymerization techniques afforded poly(amic acid) (III) of high molecular weight in the first step. An open-chain precursor subsequently underwent thermal cyclodehydration along the polymer chain at 200–350°C. in the second step, to give in quantitative yield a fully aromatic polybenzoxazinone (IV) of outstanding heat stability both in nitrogen and in air. The poly(amic acid) is soluble in N-methyl-2-pyrrolidone, and tough, transparent films can be cast from solution. Insoluble aromatic polybenzoxazinone films which possess excellent oxidative and thermal stability were obtained by the heat treatment of the polyamic acid. A detailed account of polymerization conditions in the low temperature solution polymerization of polybenzoxazinones is given, and the reaction mechanisms of cyclopolycondensation of poly(amic acids) and the formation of polybenzoxazinones are discussed.     

Cyclopolycondensations

Fully aromatic polyquinazolinediones of high molecular weight were prepared by the cyclopolycondensation reaction of 4,4′-diamino-3,3′-biphenyldicarboxylic acid with aromatic diisocyanates. The poly(phosphoric acid) solution polymerization techniques yielded tractable poly(urea acid), which was converted to polyquinazolinediones by thermal cyclodehydration at 300–400°C. under reduced pressure. The polyquinazolinediones thus obtained have excellent thermal stability both in nitrogen and in air. The poly(urea acid) is soluble in dimethyl sulfoxide, and films can be cast from the polymer solution of poly(urea acid) (η_inh = 0.8 to 1.8). The films are made tough by being heated in nitrogen or under reduced pressure at 300–400°C. The polymerization mechanism of the cyclopolycondensation reaction was studied, and it was established that the polymerization proceeded through the formation of tractable poly(urea acid), Structure (I), of high molecular weight, followed by cyclodehydration, yielding poly(1,2-dihydro-2-imino-4H-3,1-benzoxazin-4-one), Structure (II). On subsequently being heated this undergoes intramolecular rearrangement along the polymer chain, giving the thermodynamically stable polyquinazolinedione, Structure (III).     

Novel polybenzoxazinones with tricyclic fused-rings

A series of polybenzoxazinones containing phenoxathiin and phenoxaphosphine units were prepared from tricyclic diacid chlorides and 4,4′-diaminobiphenyl-3,3′-dicarboxylic acid and 4,4′-diamino-3,3′-diphenylmethane dicarboxylic acid. The low temperature solution polymerization technique afforded polyamic acid which subsequently underwent cyclization along the polymer chain in a solvent mixture of refluxing N,N′-dimethylacetamide, acetic anhydride, and pyridine to give polybenzoxazinones in moderate yields. The polymers thus obtained had inherent viscosities in the range of 0.15–0.23 dL/g, were sparingly soluble in N-methyl-2-pyrrolidone, and were found to be thermally more stable than the corresponding open-chain polymer with diphenylether linkage.     

N-methyl-substituted aromatic polyamides

A series of N-methyl-substituted aromatic polyamides derived from the secondary aromatic diamines 4,4′-bis(methylamino)diphenylmethane, 3,3′-bis(methylamino)diphenylmethane, 4,4′-bis(methylamino)benzophenone or 3,3′-bis(methylamino)benzophenone and isophthaloyl dichloride, and terephthaloyl dichloride or 3,3′-diphenylmethane dicarboxylic acid dichloride was prepared by high-temperature solution polymerization in s-tetrachloroethane. Compared with analogous unsubstituted and partly N-methylated aromatic polyamides, the full N-methylated polyamides exhibited significantly lower glass transition temperatures (T_g), reduced crystallinity, improved thermal stability, and good solubility in chlorinated solvents.     

Polymers with quinoxaline units. III. Polymers with quinoxaline and thiazine recurring units

Six ladder or partly ladder polymers have been prepared by the condensation reactions of combinations of two diaminodithiophenols, 4,6-diamino-1,3-dithiophenol and 3,3′-dimercaptobenzidine, with three tetrachloroquinoxaline derivatives, 2,3,7,8-tetrachloro-1,4,6,9-tetraazaanthracene, 2,2′,3,3′-tetrachloro-6,6′-bisquinoxaline, and 2,2′,3,3′-tetrachloro-6,6′-diquinoxalyl ether, with the use of dimethylacetamide, hexamethylphos phoramide, and polyphosphoric acid as reaction media. The polymers thus obtained are highly colored, powedery materials which are slightly soluble in methanesulfonic acid and concentrated sulfuric acid. These polymers (η_inh > 1) show good thermal stability.     

Polyquinoxalines. III

Six thermally stable polyquinoxalines have been prepared by the reactions of combinations of three tetraamines, 3,3′,4,4′-tetraaminodiphenyl sulfone (II), and 3,3′,4,4′-tetraaminodiphenyl ether (V), with two bisglyoxals, 4,4′-diglyoxalyldiphenyl sulfide dihydrate (III) and 4,4′-diglyoxalyldiphenyl sulfone dihydrate (IV). The polymers were prepared from polymerization in two stages. The first stage, a solution polymerization, produces an initially low or moderate molecular weight material, which is advanced to a high molecular weight (η_inh > 1.0) by heating at 375°C. under reduced pressure. All the polyquinoxalines have excellent thermal stability both in nitrogen and in air and improved solubility.     

The synthesis of a precursor of polybenzimidazole (PBI) and blends with polyamic acid (PAA)

The precursor of polybenzimidazole (PBI), poly(3,3′-diamino-4,4′-benzidine isophthalamide) (PDABI), was synthesized from poly(3,3′-dinitro-4,4′-benzidine isophthalamide) (PDNBI) by reduction. With increasing temperature, the NH₂ moiety which was protected by SnCl₅^?1 could cyclize and form PBI. Blends with polyamic acid (LaRC-TPI) were prepared. Clear blend films were prepared at up to 400°C. The IR spectra displayed shifts in the NH stretching band, thereby providing evidence for specific interactions related to the miscibility of their cured blends. © 1993 John Wiley & Sons, Inc.     

Cyclopolycondensations. VII. Preparation of aromatic poly(ureido acids) by the low-temperature solution polymerization and cyclodehydration to fully aromatic polyquinazolinediones

Fully aromatic polyquinazolinediones (IV) of high molecular weight were obtained by thermal cyclodehydration of aromatic poly(uredio acids) (III) prepared by the polyaddition reaction of 4,4′-diaminobiphenyl-3,3′-dicarboxylic acid (I) with aromatic diisocyanates (II). From the kinetic study of reactions of model systems (anthranilic acid with phenyl isocyanate) in the presence of a variety of basic catalysts, it was established that tertiary amines had the highest catalytic activity for the formation of ureido linkage. The optimum polymerization conditions were determined by the study of reaction variables such as monomer concentration, polymerization temperature, monomer ratio, and catalyst concentration. The effect of polarity and purity of organic solvents and reactants was also studied.     

Polyamides containing arylene sulfone ether linkages

Polyamides containing arylene sulfone ether linkages were synthesized from 4,4′-[sulfonylbis(p-phenyleneoxy)] dibenzoyl chloride (SPCI), 3,3′-[sulfonylbis(p-phenyleneoxy)] dibenzoyl chloride (SMCl), and arylene sulfone ether diamines (SED), by solution and interfacial polymerization techniques. In solution polymerization, the effect of various acid acceptors such as propylene oxide (PO), lithium chloride (LiCl)/lithium hydroxide (LiOH), and triethylamine (TEA) on molecular weight of the polyamides was studied. The effect of methyl substituted and unsubstituted aromatic sulfone ether diamines on molecular weight and thermal properties of polyamides was also studied. The polyamides prepared were characterized by solution viscosity, elemental analysis, thermal gravimetric analysis, differential scanning calorimetry, and x-ray diffraction. Physical and thermal properties of polyamides prepared from SPCl and SED were compared with the polyamides prepared from SMCl and SED.     

The block copolymers and polymer blends of nylon 6 with poly(4,4′-diphenylsulfone terephthalamide). I. Preparation and thermal properties

In this study, the flexible nylon 6 was reinforced by the rigid-chain aromatic polyamide, poly(4,4′-diphenylsulfone terephthalamide) (PSA). Various high molecular weight block copolyamides were synthesized by solution polymerization using 4,4′-diisocyanatodiphenylmethane (MDI) or p-aminophenylacetic acid (p-APA) as a coupling agent, respectively. Their thermal properties had shown that block copolyamides exhibited higher T_g and T_m, and better thermal stability, especially those using p-APA as a coupling agent. Decrease in thermal stability of block copolyamides based on MDI coupling agent was due to its urea linkage which been explained and proved by the infrared spectra data. On the other hand, the PSA molecules could act as “nucleating agents” among the nylon 6 matrix in the polymer blends, and accelerated the growth rate of crystallization of nylon 6 molecules, even though high molecular weight of PSA was used.     

Synthesis of polyimide and poly(imide-benzoxazole) in polyphosphoric acid

A polyimide made from 4,4′-diaminodiphenyl ether (ODA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was synthesized in polyphosphoric acid. Although the polymerization proceeded heterogeneously, a polyimide with an inherent viscosity of 0.90 was obtained, and a tough and flexible film was made from this polyimide. This polymerization was a one-step reaction including polycondensation and imidization; this was also confirmed by a model reaction between aniline and phthalic anhydride. Utilizing this polymerization method, 3,3′-dihydroxy-4,4′-diaminobiphenyl and 2 mol of 4-aminobenzoic acid were reacted in PPA, then BPDA was reacted to obtain an alternate copolymer containing imide and oxazole rings. This reaction gave a homogeneous solution of the poly(imide-benzoxazole). © 1993 John Wiley & Sons, Inc.     

Miscible polybenzimidazole blends with a benzophenone-based polyimide

Miscible blends of the aromatic polybenzimidazole, poly(2,2(m-phenylene)-5,5′-benzimidazole) (PBI), and the aromatic polyimide formed from 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 3,3′-diaminobenzophenone (LaRC TPI) have been prepared. Blends with PBI were prepared in N,N-dimethylacetamide solution starting with either the polyamic acid or a 95% imidized form of LaRC TPI; the blend was then precipitated into water or cast as films. The mixture was then imidized thermally to obtain PBI/LaRC TPI blends. Evidence for miscibility was obtained in the form of single composition dependent T_g's intermediate between those of the component polymers and single tan δ dynamic mechanical relaxation peaks. The IR spectra displayed shifts in the N? H stretching band, thereby providing evidence for specific interactions related to the miscibility of these two polymers.     

Thermooxidatively stable articulated benzobisoxazole and benzobisthiazole polymers

Articulated all-para polymers with 2,6-benzobisoxazole and 2,6-benzobisthiazole units in the backbone weree synthesized by copolycondensation in polyphosphoric acid of 4,6-diamino-1,3-benzenediol dihydrochloride and 2,5-diamino-1,4-benzenedithiol dihydrochloride, respectively, with terephthalic acid and reactive 3,3′-biphenyl or 4,4′-(2,2′-bipyridyl) monomers. Inherent viscosities of up to 13.18 dL/g (CH₃SO₃H, 25°C, 0.2 g/dL) were achieved. The average length of the rodlike all-para segments between the relatively flexible biphenyl or bipyridyl units was controlled by the stoichiometry of the copolycondensation reactions. Dependent upon the solids content of the polymerization mixture and the mole proportion of the flexible units in the polymer backbone, copolycondensation proceeded in the liquid-crystalline state to give polymerization mixtures which exhibited lower bulk viscosities than comparable copolycondensation reactions that remained in the isotropic state. Films which exhibited optical birefringence under crossed polars could be cast from methanesulfonic acid solutions of the polymers. Thermooxidative stability of the articulated polymers was evaluated by isothermal aging in air at 371°C. Stability for the polymers was found to decrease slightly with increased content of the flexible biphenyl structure in the polymer backbone. The biphenyl structure was found to be more thermooxidatively stable than the bipyridyl structure.     

Thermally stable polymers from 1,4,5-naphthalene–tricarboxylic acid and aromatic tetramines

New thermally stable polymers that contained benzimidazole and benzimidazobenzoisoquinoline fragments in polymer chains were synthesized by one-stage cyclopolycondensation of aromatic tetramines (3,3′, 4,4′-tetraminodiphenyl ether, 3,3′,4,4′-tetraminodiphenyl methane, 3,3′,4,4′-tetraminodiphenyl sylfone, and 3,3′-diaminobenzidine) with 1,4,5-naphthalene tricarboxylic acid 4:5–anhydride in polyphosphoric acid and with 1,4,5-naphthalene tricarboxylic acid 4:5–anhydride 1-phenyl ester. All polymers obtained were soluble in concentrated sulfuric acid, 85% phosphoric acid, polyphosphoric acid, methane sylfonic acid. Some were soluble in formic acid. Thermogravimetric analyses indicated that these polymers were stable up to 450–500°C in air. The polymers had good hydrolytic stability.     

Poly(arylene thioether) synthesis via nitro‐displacement reaction

High molecular weight poly(arylene thioether)s containing trifluoromethyl groups were prepared through the aromatic nucleophilic nitro‐displacement reaction of a dinitro monomer with aromatic dithiols. The high reactivity of the monomer, 4,4′‐dinitro‐3,3′‐bis(trifluoromethyl)biphenyl(1), activated by o‐trifluoromethyl groups and complete exclusion of oxygen was critical for the successful polymerization without any disulfide formation. The resulting trifluoromethylated poly(arylene thioether)s ( P1 and P2 ) were amorphous, dissolved in common organic solvents, and showed superior thermal properties compared to commercial poly(phenylene sulfide). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2440–2447, 2006     

A brief report on novel polyazobenzoxazinones

Polybenzoxazinones were synthesized by solution polycondensation from five different aromatic diacidchlorides and 3,3′-diaminoazobenzene-4,4′-dicarboxylic acid through a polyamic acid precursor which was further cyclodehydrated to polybenzoxazinones. The amic acid and the benzoxazinones were obtained in 85–93% and 56–63% yield, respectively. The polymers were characterized by physical and thermal analysis.     

Synthesis of aromatic polyethers by Scholl reaction. I. Poly(1,1′-dinaphthyl ether phenyl sulfone)s and poly(1,1′-dinaphthyl ether phenyl ketone)s

A novel synthetic method for the preparation of high molecular weight aromatic polyethers is presented. It consists in the Scholl reaction of di(1-naphthyl) ethers of aromatic derivatives exhibiting lower nucleophilicity and higher oxidation potential than the 1-naphthoxy groups. The examples described in this paper refer to the synthesis of aromatic polyether sulfones and aromatic polyether ketones by the polymerization of 4,4′-di(1-naphthoxy)diphenyl sulfone and respectively 4,4′-di(1-naphthoxy)benzophenone. Both polymerization reactions are performed at room temperature in nitrobenzene, using anhydrous FeCl₃ as catalyst, and apparently follow a “reactive intermediate polycondensation” polymerization mechanism.     

Novel Non‐Coplanar and Tertbutyl‐Substituted Polyimides: Solubility,Optical, Thermal and Dielectric Properties

A novel aromatic diamine monomer bearing tertbutyl and 4‐tertbutylphenyl groups, 3,3′‐ditertbutyl‐4,4′‐diaminodiphenyl‐4′′‐tertbutylphenylmethane (TADBP), was prepared and characterized. A series of non‐coplanar polyimides (PIs) were synthesized via a conventional one‐step polycondensation from TADBP and various aromatic dianhydrides including pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (OPDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) and 4,4′‐(hexafluoroisopropylidene)dipthalic anhydride (6FDA). All PIs exhibit excellent solubility in common organic solvents such as N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), N‐methyl‐2‐pyrrolidone (NMP), dimethyl sulfoxide (DMSO), chloroform (CHCl₃), tetrahydrofuran (THF), and so on. Furthermore, the obtained transparent, strong and flexible polyimide films present good thermal stability and outstanding optical properties. Their glass transition temperatures (T_gs) are in the range of 298 to 347°C, and 10% weight loss temperatures are in excess of 490°C with more than 53% char yield at 800°C in nitrogen. All the polyimides can be cast into transparent and flexible films with tensile strength of 80.5–101 MPa, elongation at break of 8.4%–10.5%, and Young's modulus of 2.3–2.8 GPa. Meanwhile, the PIs show the cutoff wavelengths of 302–356 nm, as well as low moisture absorption (0.30% –0.55%) and low dielectric constant (2.78–3.12 at 1 MHz).     

Preparation of silicon containing polymers. II.. Effect of structure on the thermal stability of organosilicon aramids

Two silicon-containing acid dichlorides, bis(4-chlorocarbonylphenyl)dimethylsilane and bis(4-chlorocarbonylphenyl)diphenylsilane, were synthesized and reacted with 1,3-phenylene diamine, 1,4-phenylene diamine, 4,4′-diaminodiphenyl, 4,4′-diaminodiphenyl methane 4,4′-diaminodiphenyl ether, and 4,4′-diaminodiphenyl sulfone in the preparation of 12 structurally different high molecular weight aromatic polyamides. A low-temperature interfacial polycondensation technique was used. Most of the polyamides formed tough, transparent, flexible films and were characterized by solubility, solution viscosity, infrared spectroscopy (IR), and glass transition temperature (T_g). The thermal behavior of these aramids was studied by dynamic thermogravimetry. The effect of diamine and acid dichloride structure on the aramids properties is also discussed.     

Bisorthoesters as polymer intermediates. II. A facile method for the preparation of polybenzimidazoles

Aromatic bisorthoesters were found to be good polymer intermediates and could be condensed with aromatic tetramines under mild conditions, in DMSO at 100°C in a relatively short reaction time to give polybenzimidazoles. The hexapropyl orthoesters of terephthalic and isophthalic acid were the preferred aromatic orthoesters because they were relatively easily purified by vacuum distillation to polymer grade intermediates, since they are liquids. Higher orthoesters distill even under good vacuum near or above the decomposition temperature of the orthoester group. Hexaethyl orthooxalate was also used and is a very useful and stable derivative of oxalic acid, which can be used for condensation reactions. These three orthoesters were used for condensations with 3,3′,4,4′-tetraaminobiphenyl, 1,2,3,4-tetraaminobenzene, 3,3′,4,4′-tetraaminobiphenyl ether, and 3,3′,4,4′-tetraaminobenzophenone. All polybenzimidazoles were obtained in high to quantitative yields and with varying molecular weights (η_inh = 0.1?0.8 dl/g), which in some cases were in the fiber forming range.