Abstract: Mixtures of salts of organic carboxylic acids and organic compounds of non-salt character, dissolved in a C.sub.1 -C.sub.4 alkanol, can be concentrated or separated with a semipermeable membrane made from a copolyamide or copolyimide-amide which contains (a) a first aromatic diamine radical and (b) a second aromatic diamine radical which carries --SO.sub.3 M groups, where M is H.sup..sym., a monovalent to polyvalent metal cation or an ammonium cation. Provided the first diamine radical contains C.sub.1 -C.sub.4 alkyl groups in the o-positions to the amino groups, the copolymers are radiation-sensitive and can be used for producing protective layers or relief images, development being carried out in an aqueous alkaline medium.

Abstract: A thermoplastic resin composition comprise 99.9.about.50 parts by weight of one or more thermoplastic resin selected from the group consisting of aromatic polyimide, aromatic polyetherimide, aromatic polyamideimide, aromatic polyethersulfone and aromatic polyether ketone and 0.1.about.50 parts by weight of one or more liquid crystal type aromatic polyimide having recurring structural units represented by the formula (1): ##STR1## wherein R.sub.1 .about.R.sub.5 is a hydrogen atom, fluorine atom, trifluoromethyl, methyl, ethyl or cyano and may be the same or different, and R is a tetravalent radical having 6.about.27 carbon atoms and being selected from the group consisting of a monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected each other with a direct bond or a bridge member.

Abstract: Di(hydroxyphenyl)benzimidazole monomers were prepared from phenyl-4-hydroxybenzoate and aromatic bis(o-diamine)s. These monomers were used in the synthesis of soluble polybenzimidazoles. The reaction involved the aromatic nucleophilic displacement of various di(hydroxyphenyl)benzimidazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds in the presence of an alkali metal base. These polymers exhibited lower glass transition temperatures, improved solubility, and better compression moldability over their commercial counterparts.

Abstract: A process for forming a polymer (and the polymer formed thereby) for passivation, resist and bonding uses, for example, that is thermally stable at relatively high temperatures in excess of 400.degree. C., but is sensitive to electromagnetic radiation. The process includes forming a heteroatom ring polymer that includes a chain formed of a large number of closed aromatic rings such as polyimide groups. According to the present teaching, intervening moieties, (that is, chemical groupings) in the form of open ring precursors of the aromatic rings, such as polyamic acid groups are introduced between the successive closed aromatic rings, which destroy and/or delimit the colinear character and the coplanar character typical of the successive aromatic rings, thus rendering the aromatic rings sensitive to structural change by electromagnetic radiation exposure, and soluble in common organic solvents, but with the exposed HRP insoluble in resist developers.

Abstract: Para-ordered aromatic heterocyclic polymers having repeating units of the formula: ##STR1## wherein n has a value of 0.05 to 1.00 and Q is a benzobisazole of the formula ##STR2## wherein X is --S-- or --O--, are soluble in aprotic solvents.

Abstract: Water-soluble rigid-rod aromatic heterocyclic polymers having repeating units of the formula: ##STR1## wherein n has a value of 0.05 to 1.

Abstract: The present invention relates to porphyrins and to metal ion-containing monomers and polymers. The monomer ##STR1## wherein A, R.sup.1,R.sup.2,R.sup.3, and R.sup.4 defined herein, is used with dianhydride to produce a porphyrin polymer or a metal ion containing porphyrin polymer. These polymers are useful as electrical conductors and as liquid crystal polymers, non-linear (NLO) materials, magnetic materials, electrochromic polymers photo-and electrocatalysts and advanced materials.

Abstract: Copolyamic acids carrying -CF3 group functionalized aromatic segments in the polymer chain derived from aromatic diamines and dianhydrides with linear-rigid-planar structure interrupted by linear-rigid-noncoplanar segments structure and the corresponding copolyimides films are provided. These copolyimides have low in-plane thermal coefficient of expansion, reduced anisotropy in the optical and dielectric properties, low moisture uptake, and improved polyimide-to-polyimide adhesion.

Abstract: A photosensitive polyimide precursor composition containing as main ingredients a poly(amic acid) wherein at least one molecular end is esterified with an alcohol, a compound containing carbon-carbon unsaturation having photoreactivity, and a photopolymerization initiator.The photosensitive polyimide precursor composition of the present invention can be prepared without the formation of any harmful by-product. When film formed from this composition is masked for patterning and then subjected to exposure and development using a developer, the amount of exposed portion dissolved in the developer until unexposed portion is dissolved off by the developer, is small and so it is possible to obtain a thick pattern. Further, by heat-treating this pattern, there can be obtained a thick polyimide pattern.

Abstract: An improved method of laminating a metal foil or sheet to a polyimide material is provided. A solution of a precursor of an intractable (i.e. thermosetting) polyimide is applied to a substrate and the solvent is removed to form a dry tack-free film. Thereafter, a solution of a precursor of a thermoplastic polyimide is applied onto the first film of polyimide and the solvent is removed to form a dry tack-free second film. Both films are then cured concomitantly at a sufficiently rapid rate and low temperature to effect substantial imidization of the polyimide precursors of both films without substantial crosslinking or densification of the polyimides in either of the films. Thereafter, a metal sheet or foil is laminated onto the thermoplastic polyimide film according to the following process. The thermoplastic film is contacted with the sheet or foil of metal to be laminated thereto.

Abstract: Novel polyimides containing pendent siloxane groups (PISOX) were prepared by the reaction of functionalized siloxane compounds with hydroxy containing polyimides (PIOH). The pendent siloxane groups on the polyimide backbone offer distinct advantages such as lowering the dielectric constant and moisture resistance and enhanced atomic oxygen resistance. The siloxane containing polyimides are potentially useful as protective silicon oxide coatings and are useful for a variety of applications where atomic oxygen resistance is needed.

Abstract: A chemical resistant copolymer useful in electronic applications, said copolymer is a polyimide containing a 3,3',4,4'-tetracarboxybiphenyl dianhydride (BPDA) moiety, at least one other dianhydride moiety, and at least one diamine.

Abstract: The diamine, 1,3-diamino-5-pentafluorosulfanylbenzene (DASP), was reacted with various dianhydrides to form polyimides containing an SF.sub.5 moiety. These polyimides exhibit high glass transition temperatures, high density, low solubility, and low dielectric properties. These polymers were used to prepare semi-permeable membranes, wire coatings, and films and are useful for electronic, space and piezoelectric applications.

Abstract: A process for preparing a polymeric composition comprising reacting a mixture of at least one phenolic compound and at least one oxazoline compound in the presence of a catalytic amount of at least one ammonium salt and a tetracarbyl phosphonium salt, and optionally also in the presence of an alkyl halide is described.

Abstract: The heat resistant adhesive of the invention comprises polyamic acid and/or polyimide which are prepared by using 1,3-bis(3-aminophenoxy)benzene as an aromatic diamine component and 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride and/or 3,3',4,4'-diphenylethertetracarboxylic dianhydride as tetracarboxylic acid dianhydrides, and further by blocking the polymer chain end with dicarboxylic anhydride or a monoamine compound; or comprises a polyimide solution containing the polyimide in a good solvent.The adhesive of the invention is a heat-resistant adhesive capable of adhering under mild temperature/mild pressure conditions. The adhesive of polyimide solution can provide desired adhesion by simple procedures such as applying to the adherend and heating under pressure and exhibits excellent adhesive strength.

Abstract: Polyethers which contain recurring units of the formula I ##STR1## in which A is a divalent aryl or heteroaryl radical,X is O, S or NR,Z is a divalent aryl or heteroaryl radical or an alkynyl, azo or (CF.sub.2) group, andR is arylare synthesized. The polyethers can be used as thermoplastics for the production of injection-molded articles, extrudates, polymer blends and coatings and for the production of films and membranes from solution.

Abstract: A silicon-modified, adhesive polyimide film composed mainly of the repetition units of the formula (I) and a process for producing a polyimide film composite product using the above film are provided, the formula (I) being ##STR1## the above process for producing a polyimide film composite product comprising subjecting the above-silicon-modified polyimide film to contact-bonding on heating to a material to be adhered, at an ultimate curing temperature of 130.degree.-230.degree. C.The above polyimide film is highly adhesive and heat-resistant in spite of heating at a relatively low temperature.

Abstract: The present invention relates to a liquid crystal alignment treating agent which comprises a polyimide resin prepared from a diamine including an aromatic diamine having at least one linear alkyl group of at least 6 carbon atoms per benzene ring as the essential component and a tetracarboxylic acid and its derivative.The liquid crystal alignment treating agent obtained in accordance with the present invention comprises a polyimide resin having an alkyl group on a side chain, and accordingly provides a liquid crystal-aligned film containing liquid crystal molecules stably having an enhanced inclined alignment angle (tilt angle) to a substrate.

Abstract: A high temperature fluorinated polyimide is made by forming a solution that includes a 3F-monomer and an aromatic or aliphatic diamine such that the solution has a ratio of 3F-monomer to diamine of greater than 1.05. The 3F-monomer is 4,4'-(2,2,2-trifluoro-1-phenylethylidene) diphthalic anhydride, a dialkylester of 4,4'-(2,2,2-trifluoro-1-phenylethylidene) diphthalic anhydride, 4,4'-(2,2,2-trifluoro-1-phenylethylidene) diphthalic acid, or mixtures thereof. The solution is mixed so the 3F-monomer reacts with the diamine to form a 3F-polyimide.

Abstract: A fluorinated condensation copolyimide has repeating polymer units that include: ##STR1## in which X and Y are diamines. The copolyimide can be made by reacting a 3F-monomer and a 6F-monomer with an aromatic or aliphatic diamine. The 3F-monomer includes 4,4'-(2,2,2-trifluoro-1-phenylethylidene) diphthalic anhydride, a dialkylester of 4,4'-(2,2,2-trifluoro-1-phenylethylidene) diphthalic anhydride, 4,4'-(2,2,2-trifluoro-1-phenylethylidene) diphthalic acid, or mixtures thereof. The 6F-monomer includes 4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene] diphthalic anhydride, a dialkylester of 4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene] diphthalic anhydride, 4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene] diphthalic acid, or mixtures thereof.

Abstract: Imide-containing phthalonitrile monomers are prepared from a phthalonitrile and an aromatic dianhydride. The monomer and a method for preparing the monomer is disclosed. These monomers are synthesized into heat resistant polymers and copolymers with aromatic ring structure incorporating imide and ether linkages. The synthesis of the high temperature thermosetting polymers and copolymers is also disclosed.

Abstract: Aromatic polyimides with acetylenic end groups are cured by coupling together thermally or catalytically using cuprous salts as catalysts to increase molecular weight with little or no by-product formation. These polyimides can be shaped and formed prior to the coupling.The acetylenic end-capped aromatic polyimides are formed by the reaction of an aromatic dianhydride, an acetylenic organic monoamine compound which will provide the reactive end groups and optionally an aromatic diamine.

Abstract: A polyimide composition for use in making polyimide/copper foil laminate that does not require an adhesive layer between the polyimide substrate and the copper foil. A polyimide precursor is first prepared from a monomer composition, which comprises a dianhydride and an imidazole-containing or benzimidazole-containing compound, or mixture thereof The polyimide precursor is then coated onto a copper foil and subsequently subject to an imidization reaction to form a polyimide/copper foil laminate, which exhibits excellent peel strength and flatness while retaining all the advantageous properties that are characteristic of polyimide resins, such as excellent mechanical strength and heat and chemical resistance. Because the polyimide/copper foil laminates disclosed in the present invention are made without the need to apply an adhesive layer, the process of manufacturing the same is greatly simplified and the cost of production therefor can be substantially reduced.

Abstract: There are described aromatic copolyamides which are soluble in organic polyamide solvents and which consist essentially of recurring structural units of the formulae Ia, Ib and Ic on the one hand and Ia, Ib and Ie on the other[--OC--R.sup.1 --CO--NH--R.sup.2 --NH--] (Ia), [--OC--R.sup.1 --CO--NH--R.sup.3 --NH--] (Ib),[--OC--R.sup.1 --CO--NH--R.sup.4 --NH--] (Ic), [--OC--R.sup.1 --CO--NH--R.sup.7 --NH--] (Ie),where R.sup.1 and R.sup.7 are divalent aromatic radicals whose valence bonds are in the para or a comparable coaxial or parallel position relative to one another, R.sup.2 is a radical of the formula III ##STR1## and R.sup.3 and R.sup.4 are radicals of the formula IV ##STR2## where Z is --O--, --S--, --CO--, --SO.sub.2 --, C.sub.1 -C.sub.10 -alkylene or --O--R.sup.1 --O-- and R.sup.6 is in each case hydrogen or an inert substituent.The mole fractions of the individual structural features in the copolyamides are defined within selected limits.

Abstract: In one aspect, the present invention relates to polyimides having excellent thermal resistance and process for preparing the same comprising carrying out condensation of 4,4'-bis(3-aminophenoxy)biphenyl with pyromellitic dianhydride in the presence of a different diamine compound and optionally with a different tetracarboxylic acid dianhydride.In a second aspect, the present invention relates to a heat resistant resin composition consisting essentially of an aromatic polyetherimide and a defined polyimide.In a third aspect, the present invention relates to a polyimide resin composition comprised on a defined polyimide and a separate high-temperature engineering polymer.In a fourth aspect, the present invention relates to a resin composition comprised of a defined polyimide and an aromatic polyamideimide.

Abstract: A thermally stable polyimide which is blocked at the polymer terminal with a dicarboxylic acid anhydride represented by the formula (III): ##STR1## wherein Z is a divalent radical selected from the group consisting of a monoaromatic radical which is substantially unsubstituted or substituted with a radical having no reactivity with amine or dicarboxylic acid anhydride and has from 6 to 15 carbon atoms, a condensed polyaromatic radical or a noncondensed aromatic radical connected each other with a direct bond or a bridge member, and has a fundamental skeleton represented by recurring structural units of the formula (IV): ##STR2## and a process of preparing the polyimide.

Abstract: This invention concerns novel fluorine-containing diamines, polyamides and polyimides. The compounds are useful in the formation of moisture resistant films, fibers and shaped articles.

Abstract: A readily processable polyimide being blocked at the terminal of a polymer molecule with a divalent radical derived from dicarboxylic acid anhydride represented by the formula (IV): ##STR1## wherein Z is a divalent radical selected from the group consisting of a monoaromatic radical which is substantially unsubstituted or substituted with a radical having no reactivity with amine or carboxylic acid anhydride and has from 5 to 15 carbons atoms, condensed polyaromatic radical or noncondensed aromatic radical connected each other with a direct bond or a bridge member, and having a fundamental skeleton represented by recurring structural units of the formula (III): wherein X and Y are --O-- or --CO-- and differ each other; preparation process of the polyimide; and resin composition containing the polyimide and fibrous reinforcement.

Abstract: Heat-resistant bonding materials are composed of a polyimide precursor end-capped at molecule ends thereof and/or an imide compound formed from the polyimide precursor. They may also contain fine particles of at least one material selected from metals, metal oxides, metal carbides and metal nitrides.

Abstract: The invention relates to a polyimide substantially built up from monomeric units of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and monomeric units of a primary aliphatic diamine. The polyimide according to the invention is characterized in that the primary aliphatic diamine is substantially 1,4-diaminobutane. The thermal stability of the polyimide according to the invention has surprisingly been found to be very good. Owing to this very good thermal stability, the polyimides according to the invention can very well be processed at--relatively--high processing temperatures without any appreciable thermal degradation of the polyimide. As a result, the polyimides processing potential has increased considerably. Also, articles made of the polyimides according to the invention can be used at significantly higher temperatures. Said articles have very good mechanical properties. Articles containing a polyimide are suited for being used in the most diverse applications.

Abstract: Polyimide having repeating units of the following formula (I) and its polyamic acid precursor having repeating units of the following formula (II) are disclosed; ##STR1## (where Y is a radical selected from the group consisting of a bond, divalent hydrocarbon having 1 to 10 carbons, hexafluorinated isopropylidene, carbonyl, thio, sulfinyl, sulfonyl and oxide, and R is a tetra-valent radical selected from the group consisting of aliphatic radical having 2 and more carbons, cyclo-aliphatic radical, monoaromatic radical, condensed polyaromatic radical, and non-condensed polyaromatic radical wherein aromatic radicals are mutually connected with a bond or a crosslinking function).Typical examples of polyimide and polyamic acid include where Y is thio radical and R is ##STR2## Y is a bond and R is III or IV, and Y is isopropylidene radical and R is IV.The polymers can be prepared from corresponding diamine and tetracarboxylic acid dianhydride.

Abstract: A favorably processable polyimide which has recurring structural units represented by the formula (I): ##STR1## wherein R is a tetravalent radical having from 2 to 27 carbon atoms and is selected from the group consisting of an aliphatic radical, alicyclic radical, monoaromatic radical, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member, and is blocked at the polymer chain end with aromatic dicarboxylic anhydride represented by the formula (II): ##STR2## wherein X is a divalent radical selected from the group consisting of a monoaromatic radical having from 6 to 27 carbon atoms, condensed polyaromatic radical and noncondensed aromatic radical connected to each other with a direct bond or a bridge member.

Abstract: Salts that contain AA-PBZ monomer ions and BB-PBZ monomer ions can be precipitated from an aqueous solution by contacting soluble salts of the monomers in an aqueous solution. The monomer salt can be polymerized by ordinary techniques to form polybenzazole polymers without the need for devolatilization and with very accurate stoichiometric control.

Abstract: A liquid crystal aligning agent containing a polymer selected from the group consisting of a polyamic acid having a steroidal skeleton and an imidized product thereof; and a liquid crystal display device to which the liquid crystal aligning agent is applied.

Abstract: A reactive oligoimide which is chemically etchable upon crosslinking, and which may serve as an adhesive for bonding at least one layer or film to another layer, preferably a flexible metallic layer to a flexible layer of an etchable polyimide, in order to form a flexible multilayer metal-clad laminate.

Abstract: The present invention provides a polyimide having all of small dielectric constant, small thermal expansion coefficient, high heat resistance, high glass transition temperature and high mechanical properties, a precursor of the polyimide, and processes for producing them. A polyimide precursor whose molecular chain comprises repeating units represented by the following general formula (1) and repeating units represented by the following general formula (2): ##STR1## wherein R.sup.1 is at least one kind of tetravalent organic group selected from the group consisting of ##STR2## R.sup.2 is at least one kind of divalent organic group having a linear structure which is selected from the group consisting of ##STR3## m is an integer of 1 to 4, and R.sup.3 is a divalent organic group having a non-linear structure which contains at least two aromatic rings.

Abstract: A fluorine-containing polyimide having a low dielectric constant, low water absorption and excellent heat resistance and moisture resistance and a precursor thereof such as a fluorine-containing polyamide-acid, can be prepared by reacting an acid anhydride with an aromatic diamine having perfluoroalkyl group.

Abstract: Polybenzoxazoles (PBO) are prepared by the aromatic nucleophilic displacement reaction of novel di(hydroxyphenyl)benzoxazole monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The polymerizations are carried out in polar aprotic solvents, such as N-methylpyrrolidine or N,N-dimethylacetamide, using alkali metal bases, such as potassium carbonate, at elevated temperatures under nitrogen. The novel di(hydroxyphenyl)benzoxazole monomers are synthesized by reacting phenyl-4-hydroxybenzoate with aromatic bis(o-aminophenol)s in the melt. High molecular weight PBO of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties. The use of the novel di(hydroxyphenyl)benzoxazoles permits a more economical and easier way to prepare PBO than previous routes.

Abstract: A readily melt-processable polyimide obtained by reacting diamino-diphenyl ether with 3,3',4,4'-biphenyltetracarboxylic dianhydride in the presence of phthalic anhydride and thermally or chemically imidizing the resultant polyamic acid.

Abstract: Polyetherimide oligomers having crosslinking end cap moieties which provide improved solvent-resistance to cured composites are generally represented by the formula: ##STR1## wherein X=--O-- or --S--; ##STR2## n=1 or 2; ##STR3## E=allyl or methallyl; R=a trivalent C.sub.(6-13) aromatic organic radical;R.sub.1 =any of lower alkyl, lower alkoxy, aryl, or substituted aryl;R'=a divalent C.sub.(6-30) aromatic organic radical;j=0, 1, or 2; andG=--CH.sub.2 --, --O--, --S--, or --SO.sub.2 --Blends generally comprise substantially equimolar amounts of the oligomers and a comparable, compatible, noncrosslinking, etherimide polymer of substantially the same backbone. The crosslinkable oligomers are made by reacting substituted phthalic anhydrides with hydroxyaryl amines and suitable crosslinking end cap reactants, or by self-condensation of phthalimide salts followed by capping the polymers.

Abstract: A readily melt processable polyimide obtained by reacting diamine represented by the formula: 4,4' ##STR1## wherein n is an integer of 1 or 2, with 3,3'4,4' -diphenylethertetracarboxylic dianhydride and/or 4,4' -(p-phenylenedioxy)diphthalic dianhydride or a mixture of these tetracarboxylic acid dianhydrides and pyromellitic dianhydride in the presence of phthalic anhydride.

Abstract: Solutions of polyimide-forming starting materials are provided containing diamines and tetracarboxylic diesters; the tetracarboxylic diesters comprise a mixture of from 0.05 to 0.95 mol % of oxydiphthalic diesters and from 0.05 to 0.95 mol % of benzophenonetetracarboxylic diesters, biphenyltetracarboxylic diesters or mixtures thereof.

Abstract: This invention is a process for the preparation of poly(aryl ethers) from cyclic poly(aryl ether) oligomers. These low melt viscosity cyclic oligomers undergo ring opening and chain extension upon heating in the presence of a catalyst, forming high molecular weight linear polymers with no coproduct formation. Finished thermoplastic parts and composites may be prepared using this technology with processing techniques normally restricted to thermosetting monomers.

Abstract: Processes for producing oriented films of semicrystalline thermoplastic polymers, such as polyimides, and films produced thereby are disclosed. One process includes partial crystallization or imidization, orientation and further crystallization or imidization. Another process includes rendering a film of semicrystalline thermoplastic polymer amorphous, orienting the film and introducing crystallinity.

Abstract: Novel polyiminocarbonates having molecular weights exceeding 70,000 daltons. Novel solution polymerization and interfacial polymerization processes for the preparation of polyiminocarbonates in which cyanate compounds are reacted with diphenol compounds in the presence of a strong base catalyst.

Abstract: There are provided fusible, rod-like graft copolymers having repeating units of the formula: ##STR1## wherein a ranges from about 0.75 to 0.97 and b is 1-a; wherein Z is a benzbisoxazole or benzbisthiazole moiety, wherein Ar is a linear phenylene or polyphenylene moiety, wherein Ar' is ##STR2## and wherein Y is a poly(etherketone) or a poly(etheretherketone), wherein the poly(etherketone) has repeating units of the formula ##STR3## wherein Q is a divalent phenylene or substituted phenylene moiety and c is an integer having a value of 1 to 4, and the poly(etheretherketone) has repeating units of the formula ##STR4## wherein Q' is a divalent phenylene or substituted phenylene moiety, d is an integer having a value of 1 to 4 and e is an integer having a value of 2 to 5.Also provided are methods for making these graft copolymers.

Abstract: A process for preparing a polyetherimide-polyimide copolymer by (a) reacting a bis (ether anhydride) with a stoichiometric excess of an organic diamine in an inert, non-polar solvent to form an amine-terminated oligomer-solvent mixture; (b) removing unreacted organic diamine from the oligomer-solvent mixture; and (c) reacting the oligomer with an aromatic dianhydride.

Abstract: A curable fluorine-containing polyimide of the formula: ##STR1## wherein R.sup.1 is a group derived from an aromatic tetracarboxylic acid dianhydride by the removal of two acid anhydride groups,R.sup.2 is a group derived from an aromatic diamine by the removal of two amino groups,A.sup.1 is a residue of the formula: ##STR2## (wherein R.sup.2 is the same as defined above, and Z is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms),A.sup.2 is a residue of the formula: ##STR3## (wherein R.sup.1 and Z are the same as defined above), and n is a number of 0 to 90, and at least one of the groups R.sup.1 and R.sup.

Abstract: Polyimide compositions, films, and electronic devices using polyimides, based on 9,9-bis(perfluoroalkyl)xanthene-2,3,6,7-tetracarboxylic dianhydride or 9-aryl-9(perfluoroalkyl)xanthene-2,3,6,7-tetracarboxylic dianhydride and 3,3',4,4'-biphenyl tetracarboxylic dianhydride or 2,2-bis(3,4-carboxyphenyl)hexafluoropropane dianhydride and benzidine derivatives which offer a combination of desirable properties including, low linear coefficient of thermal expansion, low moisture absorption, high glass transition temperature, low dielectric constant, and improved tensile elongation.

Abstract: A method for the preparation of a polyimide containing reversible crosslinks comprising the step of curing a monomer having the formula ##STR1## wherein R and R' may be the same or different and each is H or lower alkyl having 1-5 carbon atoms under conditions conducive to the formation of a polyimide and thereby forming a polyimide having the formula ##STR2## R and R' are as defined above and n is an integer from 10 to 100. The polyimide may be converted to a soluble polymer by cleaving the disulfide bond in the presence of a solvent and a reducing agent. The reduced polymer may be reformed into the polymer in an oxidation step or into a modified polyimide in other reaction steps. Copolymerization processes are also disclosed.