Synthesis and Properties of New Polyphenylquinoxaline-imide-amides

Abstract

New thermostable polymers containing imide and phenylquinoxaline units have been prepared by solution polycondensation of diaminophenylquinoxaline coupled by ether, methylene, or sulfone linkages with diacid chlorides containing preformed imide rings. Solubility, thermal stability, and electroinsulating properties of these compounds are discussed and compared with those of related heterocyclic polymers previously reported.     

Heterocyclic Polyimides

This paper presents the synthesis of certain polyimides which contain one of the following heterocycles: oxadiazole, benzox-azinone, benzthiazole. Their properties, particularly thermal stability and hydrolytic stability, are compared to fully aromatic polyimides. Poly-1,3,4-oxadiazole-imides have been synthesized either by the reaction of ditetraeole monomers which contain preformed imide cycles with diacid chlorides, or by the reaction of an aromatic diamine containing a preformed oxadiazole ring with diacid chlorides containing preformed imide rings. Polybenz-oxazinone-imides have been synthesized by polycondensation of a bis(amino acid), 4,4′-diaminodiphenylmethane-3,3′-dicarboxylic acid, with diacid chlorides containing preformed imide rings. Polybenzthiazole-imides have been obtained by polycondensation of aromatic diamines containing a preformed benzthiazole ring with diacid chlorides containing preformed imide rings. Thermal stabilities of these heterocyclic polyimides are similar and in certain cases are higher than those of fully aromatic polyimides. It was also found that the hydrolytic stability of heterocyclic polyimides is definitely superior to that of aromatic polyimides.     

Poly(1,3,4-oxadiazole-amide)s containing pendent imide groups

A series of new poly(1,3,4-oxadiazole-amide)s containing pendent imide groups has been synthesized by solution polycondensation of aromatic diamines containing preformed 1,3,4-oxadiazole rings with two diacid chlorides containing imide rings. These polymers were also prepared by the reaction of the same diacid chlorides with p-aminobenzhydrazide which were subsequently cyclodehydrated in solid state. The polymers were soluble in polar amidic solvents and some of them gave transparent flexible films by casting from solutions. They showed high thermal stability with decomposition temperatures above 400°C and glass transition temperatures in the range of 245–327°C. They had low dielectric constants, in the range of 3.32–3.94, and good tensile properties.     

Heterocyclic polyamides containing hexafluoroisopropylidene groups

New heterocyclic polyamides have been synthesized by solution polycondensation of aromatic diamines containing phenylquinoxaline units with diacid chlorides having both imide and hexafluoroisopropylidene (6F) groups. These polymers are soluble in polar aprotic solvents, such as N-methylpyrrolidone (NMP) or N, N-dimethylformamide (DMF), and can be cast into flexible thin films from solutions. They show high thermooxidative stability with decomposition temperatures above 400°C and glass transition temperatures in the range of 225-300°C. The polymer films exhibit good chemical resistance towards diluted acids and good electrical insulating properties with dielectric constants in the range of 3.2–3.7.     

Synthesis and properties of new polyamide-imides

Several new amide—imide polymers of good thermal stability have been synthesized by the reaction in solution of diacid chlorides with diamines containing cyclic imide linkages. Since these polymers incorporate preformed imide groups, they are not subject to some of the problems encountered in the preparation of polyimides by cyclizing polyamic acids. Their solutions in polar solvents such as dimethylacetamide are stable and will tolerate considerable proportions of hydrocarbon thinners without precipitation. Thick films can be cast from the solutions without degradation. A high-temperature cure is not needed to produce tough, flexible films. The powdered polymers can be molded readily.     

COMPARED PROPERTIES OF FLUORINATED HETEROCYCLIC COPOLYIMIDES

Various new fluorinated heterocyclic copolyimides have been synthesized by a polycondensation reaction of a diacid chloride containing imide, hexafluoroisopropylidene and methylene groups with aromatic or heteroaromatic diamines containing preformed phenylquinoxaline or 1,3,4-oxadiazole rings. Other fluorinated heterocyclic copolyimides have been prepared by a polycondensation reaction of the same diacid chloride with aromatic dihydrazides, bis(o-hydroxy-amine)s or a bis(o-carboxy-amine), resulting in intermediate polyhydrazides, poly(o-hydroxy-amide)s or poly(o-carboxy-amide), respectively, which were futher cyclodehydrated to the corresponding polyoxadia zole-imide, polybenzoxazole-imide or polybenzoxazinone-imide structure. These polymers showed good solubility in polar amidic solvents, such as N-methylpyrrolidinone (NMP) and dimethylformamide (DMF), and even in less polar liquids, like tetrahydrofurane or pyridine, except for those compounds containing benzoxazole rings which were less soluble, only on heating in NMP or DMF. The weight average molecular weight measured for tetrahydrofurane-fully-soluble polymers are in the range of 12800–26700 and the polydispersity is in the range of 2–5. All these polymers exhibited good thermal stability, with decomposition temperature being above 350°C, although somewhat lower than that of related polymers prepared by using fully aromatic diacid chlorides instead of the present ones containing methylene units. The glass transition temperature is in the range of 200–300°C. The dielectric constant measured for polymer films is in the range of 3.3–3.7. Tensile strength is in the range of 35–70 MPa, elongation to break between 30–40% and tensile modulus in the range of 170–330 MPa. A study of the relation between conformational parameters and properties of some of these polymers has been carried out by using the Monte Carlo method with an allowance for hindered rotation, and the values were compared with the experimental data and discussed in relation with the rigidity of the chains. The present polymers are potential candidates for use as high performance materials.     

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.     

Benzheterocycle–imide and amide–imide fibers derived from diacid chlorides containing preformed imide groups

Fibers of benzoxazole–imide ordered copolymers were prepared by cyclodehydrating the amide–phenol units of precursor polyamide–o-hydroxyimide fibers at 375°C in nitrogen. The precursor polyamide–o-hydroxyimides were obtained by the reaction of 3,3′-dihydroxybenzidine with diacid chlorides containing preformed imide rings. The benzoxazole–imide fibers are very thermally stable, especially with respect to retention of tensile properties after heat aging in air. For example, the benzoxazole–imide fibers after heating aging in air for 35 days retained 75% or more of their original tenacities and 50% or more of their original elongations to break. The original fibers did not have high tenacities, probably because of the rather extreme thermal treatment required to cyclodehydrate the amide–phenol units of the precursor fiber. The ultraviolet light stability of one benzoxazole–imide fiber was outstanding for a fiber of the polyheterocycle type: there was no loss in strength or elongation after 140 hr of exposure in a Fade-Ometer. Fibers of ordered amide–imide polymers based on the same imide-containing diacid chlorides used for the benzoxazole–imide polymers were also prepared. They were substantially less thermally stable than their benzoxazole–imide fiber counterparts, as expected.     

Regular Copolyamides. III. Preparation and Characterization of Regular Aliphatic/Aromatic Copolyoxamides

Regular aliphatic/aromatic copolyoxamides were prepared from diamine-oxamides and aromatic diacid chlorides by interfacial and solution polymerization. Solution polymerization in chloroform or dimethylacetamide is preferred for the preparation of large quantities of polymers but interfacial polymerization is most conveniently carried out for the preparation of polymers with high molecular weight. Aromatic diacid chlorides used included the diacid chlorides of terephthalic acid, isophthalic acid, 2,6-pyridinedicarboxylic acid, two isomeric naphthalene dicarboxylic acids, two cyclo-hexanedicarboxylic acid isomers, as well as 1,1-cyclobutane-dicarboxylic acid. Copolymers of diamine-oxamides with mixtures of acid chlorides of isophthalic and pyridine dicarboxylic acid and isophthalic acid/tetrachloroterephthalic acid have also been prepared. Most polymers are film-forming and are soluble in concentrated sulfuric acid, trifluoroacetic acid, and dimethylacetamide (containing several per cent LiCl). A number of these polymers gave dense or asymmetric membranes, particularly the polymers from ethylene diamine as the aliphatic diamine, particularly poly(iminoethyleneimino-oxalyliminoethyleneiminoisophthaloyl) (p-222I). Diamine oxamides with more than two amide groups in the molecules have been prepared, and in one case polymers with aromatic diacid chlorides have been prepared by interfacial polymerization. All regular aliphatic/aromatic copolyoxamides are high-melting and generally decompose above 350°C without melting. They can, however, be fabricated from solution into brittle fibers or into desalination membranes.     

Polymers containing phenylquinoxaline rings

The synthesis and properties of poly(phenylquinoxalines) containing hexafluoroisopropylidene or silylene units in the backbone are described. The polymers have been prepared by polycondensation of aromatic diamines containing preformed phenylquinoxaline rings with a dianhydride or diacid chlorides containing hexafluoroisopropylidene groups, or with a dianhydride or diacid chlorides containing silylene units. The solubility, thermal stability, film forming ability, and electric insulating, mechanical, and electroluminescent properties of the thin films are discussed and compared with those of related heterocyclic polymers. Potential applications of poly(phenylquinoxalines) are outlined.Based on the report presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (Moscow, May 30–June 4, 2004).Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1739–1748, September, 2004.     

Polybenzimidazole-Ester-Imides

Thermostable heterocyclic polymers containing benzimidazole and imide rings, as well as flexible ester groups, have been synthesized by solution polycondensation of diaminobenzimidazoles with dianhydrides incorporating preformed ester linkages. The thermal stability and the electrical insulating properties of these products are discussed and compared with related heterocyclic polymers.     

Synthesis of difunctional polystyrenes and their incorporation in block copolymers with bisphenol a polycarbonate

Block polymers of polystyrene and bisphenol A polycarbonate have been prepared and their bulk viscosities studied as functions of both shear stress and polystyrene block length. The polystyrene blocks were α,ω-diacid chlorides prepared from the reaction of “living” polystyrenes with diacid chlorides. These reactions were studied in order to discover the most effective way of preparing the polystyrene diacid chlorides. The polystyrene diacid chlorides are best prepared by reaction of disodiopolystyrene with phosgene. The flow properties of the block copolymers depend on the composition of the polymers but do not depend on the length of the polystyrene blocks.     

Poly(siloxaneimide)s 2. Polycondensation of some imidic diacid chlorides with aminoalkylsiloxanes

Some new poly(siloxaneimide) copolymers with good solubilities have been synthesized by solution polycondensation of aromatic diacid chlorides containing preformed imide rings with disiloxanes and siloxane oligomers having α,ω-aminopropyl functionalities. The polycondensation reactions were carried out using equimolecular amounts of the two monomers, in polar aprotic solvents and inert atmosphere.The obtained compounds were characterized by elemental C, H, and Si analysis, solubility measurements, IR and 1H-NMR spectrometry. Thermogravimetric curves were also recorded. All data agree with the proposed structures.     

New polymer syntheses XII. Polyketones based on diarylidenecycloalkanones

Two new series of polyketones containing diarylidene links was synthesized by the Friedel-Crafts polymerization of diarylidenecyclopentanone or diarylidenecyclohexanone with aromatic diacid chlorides, azodibenzoyl chlorides, or aliphatic diacid chlorides. The resulting polymers had inherent viscosities in the range 0.76-1.18 dl/g and showed poor solubilities to common organic solvents excepts strong acids. The thermal stabilities of these polymers were evaluated and correlated to their structural units by thermogravimetric analysis (TGA), DTG and DSC measurements. The TGA data revealed 10% weight losses at 190-300 °C. Moreover, the crystallinity of some polymers were tested by X-ray analyses and the UV-visible spectra showed characteristic absorption bands in the range 240-350 nm.     

Self-regulating polycondensations: Ordered aromatic polyamide-esters

The polycondensation of aminophenols with diacid chlorides was examined to determine if the amide-ester polymers obtained are random or ordered. All of the evidence obtained points to the conclusion that ordered copolymers indeed are prepared and that a “self-regulating” polymerization process is operating by virtue of the considerably greater reactivity of aromatic amino groups relative to phenol groups. The first step of the reaction involves the in situ preparation of a diphenol-amide which undergoes further condensation. The diphenol-amide intermediate may be isolated or reacted in situ. In addition to the ordered polymer from a given aminophenol and a single diacid chloride, ordered copolymers from two different diacid chlorides were prepared in which the diacid moieties appear in an alternating fashion; the structure of such polymers depends on the order of addition of the diacid chlorides. Corresponding polymers also may be prepared from the preformed diphenol-amide monomers. The molecular weights of certain of the polymers were sufficient for the preparation of films which could be hot-stretched severalfold. Interfacial polycondensations gave polymers of higher inherent viscosities than did solution polymerizations when aminophenols or diphenol-amide monomers were condensed with diacid chlorides.     

New cohort of optically active nanostructure poly(amideimide)s: Production and properties

Novel aromatic-aliphatic poly(amide-imide)s containing chiral units in the main chain and hydroxyl benzamide units in the side chain have been obtained from the step-growth polymerization of 3,5-diamino-N-(4-hydroxyphenyl) benzamide(2) with different chiral diacid chlorides(1a-1e).Theoretical calculations were done by means of computational chemistry methods to narrate the stable conformation and orientation of each diacid chloride monomers under reaction conditions.These polymers were characterized by conventional techniques.The resulting polymers show good thermal stability.Other physical properties of polymers including crystallinity,inherent viscosity and morphological characteristics were also studied.     

Structure-property relations in heat resistant polyesters with built-in ether and imide units

A new pyridine-based diacid containing ether and imide units was synthesized via reaction of 5-amino-1-naphthol with 2,6-dichloropyridine in the presence of potassium carbonate in N-methyl-2-pyrrolidone (NMP), and subsequent reaction of the obtained diamine with 2 mol of trimellitic anhydride. A series of poly(ether imide ester)s was synthesized by the polycondensation reactions of the prepared diacid with different diols via high temperature solution polycondensation reaction method. All the products were fully characterized by common spectroscopic methods. The polymers were examined by elemental analysis, IR and ¹H NMR spectra, inherent viscosity, X-ray diffraction, DSC, TGA and DMTA and their properties were studied. Polymers showed high thermal stability and good solubility in polar aprotic solvents. The Structure-property relations of the polymers were also studied.     

Synthesis and characterization of novel heat resistant poly(amide imide)s

A series of new poly(amide imide)s was prepared from new diacid containing sulfone, ether, amide and imide groups with various aromatic diamines. The diacid was synthesized via four steps, starting from reaction of 4-aminophenol with 4-nitrobenzoyl chloride in the presence of propylene oxide afforded N-(4-hydroxy phenyl)-4-nitrobenzamide. In the second step, reduction of nitro group resulted in preparation of 4-amino-N-(4-hydroxy phenyl) benzamide. In the next step for the preparation of diamine, the reaction of 4-amino-N-(4-hydroxy phenyl) benzamide with bis-(4-chlorophenyl) sulfone in the presence of K₂CO₃ was achieved. The prepared sulfone ether amide diamine was reacted with two moles of trimellitic anhydride to synthesize related sulfone ether amide imide diacid. The precursors and final monomer were characterized by FT-IR, H-NMR and elemental analysis. Direct polycondensation reaction of the sulfone ether amide imide diacid with different diamines in the presence of triphenyl phosphite afforded five different poly (sulfone ether amide imide amide)s. The obtained polymers were fully characterized and their physical properties including thermal behavior, thermal stability, solubility, and inherent viscosity were studied.     

Synthesis and properties of novel aromatic polyamides based on 4-aryl-2,6-bis(4-chlorocarbonylphenyl) pyridines

A facile synthesis of three new diacid chlorides containing pyridine ring bearing aromatic type pendant groups on its 4-position is described. The monomers were characterized by FTIR, 1HNMR, mass spectroscopies and elemental analysis. Polycondensation reactions of the prepared diacid chlorides with different commercially available diamines resulted in the preparation of novel polyamides. Optimal conditions for polyamidations were obtained via study of the model compounds. The polymers were characterized by FTIR, 1HNMR, and elemental analysis and their physical properties including solution viscosity, solubility properties, thermal stability and thermal behavior were studied as well. The polyamides show excellent thermal stability and solubility in polar aprotic solvents.     

Synthesis and properties of polyketones containing thiophene links

A series of polyketones containing thiophene links was synthesized by the Friedel-Crafts polymerization of these dithienylalkanes with aromatic diacid chlorides or dicarbonyl chlorides comprising thiophene links with diphenyl compounds. The resulting polymers had inherent viscosities in the range of 0.11–0.27 dL/g and showed poor solubilities to common organic solvents except strong acids. These thiophene-based polyketones exhibited fairly good thermal stabilities. The TGA data revealed 5% weight losses at 375–450°C and residual weights at 500°C were 43–79% under nitorgen. It was found that the thermal stabilities of these polymers were superior to those of polymides or polysulfonamides containing thiophene links and almost comparable to common aromatic polyketones