Abstract: A method for preparing polyamic acid and polyimide, which is suitable for use in adhesives or adhesive tapes for electronic parts. The polymers have such three-dimensional molecular structures that a significant improvement can be brought about in solvent solubility, thermal resistance, mechanical properties, and adhesive properties onto various substrates. The polyamic acid is prepared by reacting at least one tetracarboxylic dianhydride, at least one aromatic diamine, at least one diamine with a siloxane structure, represented by the following general formula I, and at least one polyamino compound represented by the following general formula II or III. The polyamic acid is converted into polyimide through thermal or chemical imidization.

Abstract: Polymerisable resins which comprise a porphyrinogenic ring system obtained by the reaction of: (a) one or more compounds selected from the group consisting of pyrrole and N-(lower)alkyl pyrroles, any of which may be optionally substituted, and (b) a C4-C6 saturated alicyclic ketone which is capable of reacting with the 2 or 5 position of the pyrrole ring. Resin coating systems comprising the said resins.

Abstract: Bis(halophthalimides) such as, 3-bis[N-(4-chlorophthalimido)]benzene are prepared in slurry in an organic liquid such as o-dichlorobenzene or anisole, by a reaction at a temperature of at least 150° C. between at least one diamino compound, preferably an aromatic diamine such as m- or p-phenylenediamine, and at least one halophthalic anhydride such as 4-chlorophthalic anhydride, in the presence of an imidization catalyst such as sodium phenylphosphinate. The solids content of the reaction mixture is at least about 5% and preferably at least about 12% by weight. The product slurry may be employed directly in the preparation of polyetherimides, and similar slurries may be employed to prepare other polyether polymers.

Abstract: Essentially colorless, transparent polyimide coatings and films prepared by combining aromatic dianhydrides with para-substituted aromatic diamines are provided. The polyimide coatings and films are produced by a process whereby the dianhydride and diamine monomer components are reacted at temperatures of greater than 80° C.

Abstract: A new poly (biphenyl ether sulfone) having improved polydispersity and also having low levels of low molecular weight oligomer.

Abstract: The invention concerns a process for preparing linear or branched sulphurous polymers such as polyarylene sulphides, in particular polyphenylene sulphide, from an aromatic dihalide compound and a sulphide in a solvent, wherein a) the aromatic dihalide compound and the sulphide are partially reacted; b) the resultant salt which is not dissolved in the reaction medium is separated off; and c) the reaction mixture largely freed of the salt is further polymerized.

Abstract: Perfluoroether acylperoxides having an average equivalent weight in the range of 350-5000, and of the following formulae: Y′—(CF2—CF(CF3)O)m—(CX′FO)n—CF2CO—O—O—CO—CF2—(OCX′F)n—(OCF(CF3)—CF2)—Y′  (I) wherein Y′=Cl, ORf wherein Rf is a C1-C3 perfluoroalkyl; m, n are integers such that the average equivalent weight of (I) is in the range of 350-5000 and m/n≧40; X′=F, CF3; T—CF2—O—[(CF2CF2O)p—(CF2O)q—CF2—CO—O—O—CO—CF2(OCF2)q—(OCF2CF2)p]y—OCF2—COOH  (II) wherein y is an integer comprised between 1 and 5; p and q are integers such as to give the above mentioned EW and p/q=0.5 to 2.0; T=COOH, F with the proviso that when T=COOH y=1-5, when T=F then y=1, and processes for manufacturing them.

Abstract: Disclosed is a process which comprises reacting a polymer of the general formula wherein x is an integer of 0 or 1, A is one of several specified groups, such as B is one of several specified groups, such as or mixtures thereof, and n is an integer representing the number of repeating monomer units, with a halomethyl alkyl ether, an acetyl halide, and methanol in the presence of a halogen-containing Lewis acid catalyst, thereby forming a halomethylated polymer.

Abstract: A process for producing polyimide microfine particles which is amenable to free control of particle morphology and particle diameter distribution is provided. A polyamic acid and a polyimide, each in the form of microfine particles with good monodispersibility, are also provided. There is also provided a process for producing polyimide microfine particles from a tetracarboxylic anhydride and a diamine compound which comprises (a) a first step of preparing a first solution containing the tetracarboxylic anhydride and a second solution containing the diamine compound, (b) a second step of mixing the first and second solutions and causing a polyamic acid to precipitate in the form of microfine particles from the mixed solution under ultrasonic agitation, and (c) a third step of imidating the polyamic acid particles to provide the objective polyimide in the form of microfine particles.

Abstract: The invention relates to a photosensitive polyimide resin composition comprising (A) a polyamic acid having, in its main chain, repeating units formed from a polycondensation product of at least one tetracarboxylic acid or tetracarboxylic anhydride thereof with at least one diamine compound, and having actinic ray-sensitive functional groups at both terminals thereof; (B) a photosensitive auxiliary having a photopolymerizable functional group; (C) a photopolymerization initiator; and (D) a solvent, wherein 1 the polyamic acid is such that when the repeating unit represented by the formula (1) is defined as a unit molecular weight, a unit molecular weight per carboxyl group (unit molecular weight/COOH) falls within a range of from 200 to 300, and 2 the photosensitive resin composition permits the formation of a polyimide film having a residual stress of 40 MPa or lower and a coefficient of thermal expansion of 30 ppm/.degree. C.

Abstract: A polymer composition made by combining a polyketone polymer and a phenolic alkylene dicarboxylate of the general formula: ##STR1## each R.sup.1 independently is hydrogen or alkyl with 1-6 carbon atoms, each R.sup.2 independently is alkyl with 1-6 carbon atoms,each m is an integer of 0-4, andn is an integer of 2-12; anda process for preparing these compositions.

Abstract: A polyimide precursor solution having a high concentration yet low viscosity, a polyimide coating film having satisfactory physical properties which is prepared from the polyimide precursor solution, and a process for producing a polyimide coating film using the polyimide precursor solution. The polyimide precursor solution has dissolved therein a specific salt of a diamine and a tetracarboxylic acid and/or a dicarboxylic acid-dialkyl ester in a high concentration, the diamine and the tetracarboxylic acid and/or the dicarboxylic acid-dialkyl ester being capable of forming a polyimide. Also disclosed is a polyimide coating film obtained by heating the solution to cause imidization and a process for producing the polyimide coating film.

Abstract: The polyimides are derived from solutions of at least one low-boiling organic solvent, e.g. isopropanol containing a mixture of polyimide-forming monomers. The monomeric solutions have an extended shelf life at ambient (room) temperatures as high as 80.degree. C. and consist essentially of a mixture of monoalkyl ester-acids, alkyl diester-diacids and aromatic polyamines wherein the alkyl radicals of the ester-acids are derived from lower molecular weight aliphatic secondary alcohols having 3 to 5 carbon atoms per molecule such as isopropanol, secondary butanol, 2-methyl-3-butanol, 2 pentanol or 3-pentanol. The solutions of the polyimide-forming monomers have a substantially improved shelf-life and are particularly useful in the aerospace and aeronautical industry for the preparation of polyimide reinforced fiber composites such as the polyimide cured carbon composites used in jet engines, missiles, and for other high temperature applications.

Abstract: Rigid-rod and segmented rigid-rod polymers, methods for preparing the polymers and useful articles incorporating the polymers are provided. The polymers incorporate rigid-rod backbones with pendant solubilizing groups attached thereto for rendering the polymers soluble.

Abstract: Polyimide is produced by reacting two kinds of diamine compounds consisting of diaminopolysiloxane and a hydroxyl group-containing diamine or three kinds of diamine compounds consisting of diaminopolysiloxane, a hydroxyl group-containing diamine and an aromatic or alicyclic diamine with a dicarboxylic acid anhydride having a 2,5-dioxotetrahydrofuryl group as one acid anhydride group, thereby once forming a polyamic acid, and subjecting the polyamic acid to polyimidization reaction. The resulting polyimide itself is soluble in low boiling organic solvents for general purpose use, typically methyl ethyl ketone. A photosensitive composition comprising the polyimide, a photo crosslinking agent and a photo acid-generating agent forms a negative type polyimide pattern upon development with an aqueous alkali solution.

Abstract: The service life of fiber-reinforced polyimide composites in a high temperature oxidative environment is extended by coating with a polyimide coating precursor solution that is synthesized by reacting an aromatic dianhydride with an aromatic diamine in a non-reactive solvent. The reactive solution is heated to a temperature sufficent to reduce its viscosity prior to its use as a coating. Preferably, a mixture of meta-phenylenediamine and para-phenylenediamine is reacted with biphenyldianhydride in n-methyl pyrrolidinone solvent and thereafter heated to between about 50.degree. C. (122.degree. F.) and 150.degree. C. (302.degree. F.) under nitrogen while stirring for a time sufficient to obtain a polyamic acid polyimide precursor coating solution having a Brookfield viscosity of from about 500 to about 5000 cP and a solids content of from about 5 to about 35 weight percent.

Abstract: Disclosed is a process which comprises reacting a polymer of the general formula ##STR1## or ##STR2## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR3## B is one of several specified groups, such as or mixtures thereof, and n is an integer representing the number of repeating monomer units, with a halomethylethyl ether, a hydrohalic acid, and acetic acid in the presence of a halogen-containing Lewis acid catalyst, thereby forming a halomethylated polymer.

Abstract: Disclosed is a composition which comprises a polymer containing at least some monomer repeat units with water-solubility- or water-dispersability-imparting substituents and at least some monomer repeat units with photosensitivity-imparting substituents which enable crosslinking or chain extension of the polymer upon exposure to actinic radiation, said polymer being of the formula ##STR1## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR2## B is one of several specified groups, such as ##STR3## or mixtures thereof, and n is an integer representing the number of repeating monomer units. In one embodiment, a single functional group imparts both photosensitivity and water solubility or dispersability to the polymer. In another embodiment, a first functional group imparts photosensitivity to the polymer and a second functional group imparts water solubility or dispersability to the polymer.

Abstract: Polymer composition made by combining a polyketone polymer and a monophenolic compound of the general formula: ##STR1## R.sup.1 and R.sup.2, independently, are hydrogen or alkyl groups with 1-6 carbon atoms,Y is an organic group from 3 up to 15 carbon atoms.

Abstract: A new holographic substrate utilizing flexible, optically transparent fluorinated polyimides. Said substrates have extremely low birefringence which results in a high signal to noise ratio in subsequent holograms. Specific examples of said fluorinated polyimides include 6FDA+APB and 6FDA+4BDAF.

Abstract: This invention relates to a poly (imide amic ester) random copolymer, a precursor thereof, and a process for preparing the same. Specifically this invention relates to a novel precursor of polyimide, poly(imide amic ester) which is chemically stable and has excellent workability in either liquid or solid state, a polyimide obtained therefrom and a process for preparing the same.

Abstract: Copolyetherimides are prepared by the reaction of an alkali metal salt of a dihydroxyaromatic compound with a bis(substituted phthalimide) and a third compound which may be a substituted aromatic ketone or sulfone or a macrocyclic polycarbonate or polyarylate oligomer. The reaction takes place the in presence of a solvent and a phase transfer catalyst having high thermal stability, such as a hexaalkylguanidinium halide. Random or block copolymers may be obtained, depending on the reaction conditions.

Abstract: A magnetic recording medium has a substrate and an non-magnetic underlayer formed on the substrate and a magnetic layer formed on the non-magnetic layer. The magnetic layer include a magnetic powder and a binder for binding the magnetic powder on the non-magnetic layer. The binder includes at least a resin component containing at least an aminoquinone structure selected from an aminoquinone structure group shown with formulas (1-1) and (1-2) as a constitutional unit. As the magnetic powder, a metal magnetic powder mainly made of Fe and having a saturation magnetization .sigma.s is used. The magnetic layer has a saturation flux density Bm of 3500 to 5000 G and a coercive force of 1800 to 3000 Oe and a surface roughness SRa of 1 to 10 nm and a thickness of not more than 1.0 .mu.m.

Abstract: The invention relates to polysulphone/polyether block copolycondensates having the recurring structural unit as in formula (I)--(--O--E--O--Ar.sup.1 --SO.sub.2 --Ar.sup.2 --)--W-- (I)whereinE is a divalent diphenolate radical andW is a polyether, polythioether or polyacetal possessing at least two hydroxyl groups and having an average molecular weight (M.sub.n) of from 400 to 30,000 andwherein the proportion of the radical W in the total polymer amounts to 5 to 99 wt. %,the preparation and use thereof for the production of moulded shapes, for example, membranes or catheter tubes.

Abstract: Macrocyclic polyether oligomers, preferably as mixtures of oligomers of different degrees of polymerization, are incorporated in a direct displacement reaction mixture for the formation of polyetherimides, said reaction mixture comprising at least one alkali metal salt of a dihydroxy-substituted aromatic hydrocarbon and at least one bis(halo- or nitrophthalimide). The macrocyclic oligomers can be isolated from an earlier-prepared linear polyetherimide composition. Their incorporation in the reaction mixture does not increase the proportion of oligomers in the polyetherimide product.

Abstract: This invention provides a polyimide precursor solution having high concentration and low viscosity and a production process thereof, and polyimide coatings and films having excellent physical properties obtained therefrom and a production process thereof. Particularly, it relates to a polyimide precursor solution which contains a salt of a specific diamine with a specific tetracarboxylic acid, as its solute; to a process for the production of the polyimide precursor solution, which comprises allowing 1 mole of a specified diamine to react with 0.3 to 0.9 mole of a specific tetracarboxylic acid dianhydride, thereby obtaining a diamine, and subsequently adding 0.95 to 1.

Abstract: Aromatic polyether polymers, illustrated by polyethersulfones, polyetherketones and polyetherimides, are prepared by a phase transfer catalyzed reaction between a salt of at least one dihydroxyaromatic compound and at least one substituted aromatic compound such as bis(4-chlorophenyl) sulfone, bis(4-chlorophenyl) ketone or 1,3-bis?N-(4-chlorophthalimido)!benzene, in a monoalkoxybenzene such as anisole as diluent and in the presence of a phase transfer catalyst, preferably a hexaalkylguanidinium salt.

Abstract: A method is provided for the preparation of polyquinoline polymers based on Friedlander condensation polymerization. The method comprises mixing monomers which, when polymerized, form a polyquinoline polymer, together with a catalyst and a solvent, wherein the catalyst comprises an alkyl phosphate.

Abstract: New polyquinoline polymers are provided, as well as new methods for preparing the polyquinoline polymers using a novel combination of monomers. The polyquinoline polymers comprise repeat units comprising at least one quinoline nucleus and at least one ether linkage and having as end groups either fluoro groups or hydroxy groups or a combination of fluoro and hydroxy groups. The polymers are formed by providing a monomer comprising two fluoro groups, where each such fluoro group is activated by a quinoline nucleus, a diol monomer provided in the form of its bis-oxide salt, or in the presence of a base capable of deprotonating the diol and reacting the difluoro and diol monomers together in a dipolar solvent to form the polyquinoline polymer.

Abstract: A method for the homopolymerization or copolymerization of vinyl chloride, wherein the inner wall of the polymerizer and the like are prevented from being fouled with the resulting polymer by applying a coating fluid containing the oxidative polymerization product of a specific phenolic monomer to the surface of the inner wall of the polymerizer and the like, as well as an anti-fouling agent used for this purpose. The method of this invention can very effectively prevent the polymerizer and the like from being fouled with the resulting polymer without affecting the polymerization rate and various properties of the product. Consequently, the necessity of performing the operation for removal of the deposited polymer after completion of each polymerization cycle is eliminated, thus making it possible to achieve closed polymerization requiring no manhole opening after each polymerization cycle which is becoming increasingly popular in recent years.

Abstract: Provided are photosensitive resin compositions comprising a polyamic compound having, at each terminal thereof, a specific actinic ray-sensitive functional group which has substituent groups each having a photopolymerizable carbon-carbon double bond, a photosensitive auxiliary having a photopolymerizable functional group and a solvent. The photosensitive resin compositions of the invention are excellent in resist properties such as sensitivity and good in storage stability and can provide a film small in residual stress.

Abstract: In the process of the present invention, a non-polar, aprotic solvent is removed from an oligomer/polymer solution by freeze-drying in order to produce IPNs and semi-IPNs. By thermally quenching the solution to a solid in a short length of time, the size of the minor constituent-rich regions is greatly reduced as they are excluded along with the major constituent from the regions of crystallizing solvent. The use of this process sequence of controlling phase morphology provides IPNs and semi-IPNs with improved fracture toughness, microcracking resistance, and other physical-mechanical properties as compared to IPNs and semi-IPNs formed when the solvent is evaporated rather than sublimed.

Abstract: Disclosed is a process which comprises reacting a polymer of the general formula ##STR1## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR2## B is one of several specified groups, such as ##STR3## or mixtures thereof, and n is an integer representing the number of repeating monomer units, with an acetyl halide and dimethoxymethane in the presence of a halogen-containing Lewis acid catalyst and methanol, thereby forming a haloalkylated polymer. In a specific embodiment, the haloalkylated polymer is then reacted further to replace at least some of the haloalkyl groups with photosensitivity-imparting groups. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymer.

Abstract: This invention provides a process wherein a stable solution of polycarbodiimide with a number-average molecular-weight of 5,000 to 60,000 can be very easily prepared by using an organic diisocyanate (e.g., 2,4-tolylene diisocyanate or 2,6-tolylene diisocyanate) as starting material, a cyclic phosphine oxide as catalyst and a chlorinated aromatic compound as solvent and by controlling certain reaction conditions within the reaction temperature range of 110.degree. to 150.degree. C.

Abstract: This invention provides a process for the preparation of a polycarbodiimide solution wherein the polycarbodiimide is synthesized by heating an organic diisocyanate (e.g., 2,4-tolylene diisocyanate or 2,6-tolylene diisocyanate) in the presence of a carbodiimidation catlayst characterized in that a non-chlorinated aromatic hydrocarbon is used as the solvent and the resulting polycarbodiimide has a number average molecular weight from about 3,000 to about 10,000; wherein the synthesis is performed in the temperature range of from about 100.degree. to about 120.degree. C.

Abstract: Disclosed is a process which comprises reacting a polymer of the general formula ##STR1## wherein x is an integer of 0 or 1, A is one of several specified groups, such as ##STR2## B is one of several specified groups, such as ##STR3## or mixtures thereof, and n is an integer representing the number of repeating monomer units, with an acetyl halide and dimethoxymethane in the presence of a halogen-containing Lewis acid catalyst and methanol, thereby forming a haloalkylated polymer. In a specific embodiment, the haloalkylated polymer is then reacted further to replace at least some of the haloalkyl groups with photosensitivity-imparting groups. Also disclosed is a process for preparing a thermal ink jet printhead with the aforementioned polymer.

Abstract: A process for intramolecularly condensing a polyamic acid composition containing an NLO compound to form a polyimide host matrix composition containing as a guest the NLO compound, which process includes the step of uniformly heating the polyamic acid composition, in the absence of a solvent or diluent, to a temperature at which the intramolecular condensation will occur without thermal degradation of the NLO compound, so that the temperature differential within the polyamic acid is below that which will produce localized thermal degradation temperatures, until the intramolecular condensation of the polyamic acid composition to the polyimide host matrix composition is substantially complete. Polyimide host matrix compositions containing guest NLO compounds prepared by the inventive process are also disclosed, wherein the NLO compounds have external field-induced molecular alignments.

Abstract: Process for carrying out gas/liquid reactions at from (-50.degree.) to 300.degree. C. and from 0.1 to 100 bar by carrying out the reaction in the absence of a continuous gas phase, and, as a special case, a process for the batchwise reaction of acetylene in the liquid phase at from 0.degree. to 300.degree. C. and from 2 to 30 bar, in which acetylene is introduced a) in the absence of a continuous gas phase and b) under isobaric conditions to a degree of saturation of from 5 to 100%.

Abstract: The present invention provides a polyimide resin composition comprising:(a) a polyamide resin comprising a repeating unit represented by the general formula (1): ##STR1## wherein X represents a tetravalent organic group represented by the formula (2): ##STR2## Y represents a divalent organic group comprising a divalent siloxane residual group represented by the formula (3): ##STR3## wherein m is an integer of 60 to 120; and a divalent aromatic group represented by the formula (4): ##STR4## wherein R.sup.1 represents a hydrogen atom or a fluorine atom; and (B) cyclohexanone. From this composition, polyimide resin films can be obtained by heating at a lower temperature for a short time, and the films obtained show good adhesion under moisture-resistant conditions.

Abstract: The invention relates to a PMR type resin which comprises a mixture of:(a) nadic acid of Formula (Ia) or a derivative thereof ##STR1## (b) a diaminobisimide of Formula (Ib) ##STR2## (c) an aromatic tetracarboxylic acid of Formula (Ic) or a derivative thereof ##STR3## the components (a), (b) and (c) being present in the approximate molar proportions of 2:n:n-1 respectively.

Abstract: An aromatic polyethersulphone incorporating sub-unit (1) where A is an electron withdrawing group, the designation "o,p" represents that the bond is at the ortho or para position to the A group, and X is selected from: OH; --O M where M is an organic or inorganic cation (other than hydrogen) and n is at least 1; --NR1R2 where R1 and R2 are the same or different and are selected from hydrogen and alkyl, aryl, aminoalkylene or ammonoalkylene groups; and --OR3 where R3 is an alkyl or aryl group; either as the only sub-units of the polymer or in combination with comonomer units.

Abstract: The present method provides a method for preparing the PI varnish which has the steps of: 1) preparing a mixed solution of 60-100% by weight aprotic solvent, and 0-40% by weight aromatic solvent; 2) adding into the mixed solution in a mole ratio of 1:9 two aromatic diamines; and 3) further adding in the mixed solution in a mole ratio of 1:5 two aromatic dianhydrides. Such PI has a suitable thermal expansion coefficient and characteristics different form those of the PI currently in use.

Abstract: A poly(imide amic ester) having repeating unit of formula (I) and a process for the preparation thereof are provided, wherein formula (I) has the structure ##STR1## wherein Ar is, ##STR2## Ar' is, ##STR3## Ar" is ##STR4## R is selected from the group consisting of CH.sub.3, CH.sub.2 CH.sub.3, CH(CH.sub.3).sub.2, CH.sub.2 CH.sub.2 CH.sub.3, CH.sub.2 (CH(CH.sub.3).sub.2 and C(CH.sub.3).sub.3. Further, processes for the preparation of polyimide, polyimide film and polyimide fiber using the above poly(imide amic ester) are provided.

Abstract: A planarizing material comprising a resin capable of having its practical temperature for a planarizing step set at a level lower than 200.degree. C., and a melamine-type heat-curing agent and/or an epoxy-type heat-curing agent.

Abstract: An aromatic polyether contains within its chain the repeat units--Ph--CO--Ph-- I--[Ph--SO.sub.2 --Ph]n-- IIat a molar ratio I/II in the range 98:2 to 80:20 where Ph represents paraphenylene; the repeat units are linked through ether oxygen; and n is at least 1.1. pa It can be made by reacting together hydroxy and halogeno aromatic compounds corresponding to units I and II and to any minor units that are to be present. The reactants can be provided at least partly by a polymer containing an ether-linked succession of the units.

Abstract: Rigid-rod and segmented rigid-rod polymers, methods for preparing the polymers and useful articles incorporating the polymers are provided. The polymers incorporate rigid-rod backbones with pendant solubilizing groups attached thereto for rendering the polymers soluble.

Abstract: New polyquinoline polymers are provided, as well as new methods for preparing the polyquinoline polymers using a novel combination of monomers. The polyquinoline polymers comprise repeat units comprising at least one quinoline nucleus and at least one ether linkage and having as end groups either fluoro groups or hydroxy groups or a combination of fluoro and hydroxy groups. The polymers are formed by providing a monomer comprising two fluoro groups, where each such fluoro group is activated by a quinoline nucleus, a diol monomer provided in the form of its bis-oxide salt, or in the presence of a base capable of deprotonating the diol and reacting the difluoro and diol monomers together in a dipolar solvent to form the polyquinoline polymer.

Abstract: Rigid-rod and segmented rigid-rod polymers, methods for preparing the polymers and useful articles incorporating the polymers are provided. The polymers incorporate rigid-rod backbones with pendant solubilizing groups attached thereto for rendering the polymers soluble.

Abstract: Rigid-rod and segmented rigid-rod polymers, methods for preparing the polymers and useful articles incorporating the polymers are provided. The polymers incorporate rigid-rod backbones with pendant solubilizing groups attached thereto for rendering the polymers soluble.

Abstract: Novel molecular weight controlled and endcapped polybenzimidazoles (PBI) are prepared by the aromatic nucleophilic displacement reaction of di(hydroxyphenylbenzimidazole) monomers with activated aromatic dihalides or activated aromatic dinitro compounds. The PBI are endcapped with mono(hydroxyphenyl)benzimidazoles. The polymerizations are carried out in polar aprotic solvents such as N-methyl-2-pyrrolidinone or N,N-dimethylacetamide using alkali metal bases such as potassium carbonate at elevated temperatures under nitrogen. Mono(hydroxyphenyl)benzimidazoles are synthesized by reacting phenyl-4-hydroxybenzoate with aromatic (o-diamine)s in diphenylsulfone. Molecular weight controlled and endcapped PBI of new chemical structures are prepared that exhibit a favorable combination of physical and mechanical properties.