Abstract: A method of forming an element to float at least partially on a surface of an at least partially liquid hydrocarbon mixture. The method includes mixing a polymer resin and a foaming agent together in preselected proportions to provide a material mixture, and heating the material mixture, to at least partially liquefy it. The material mixture is injected into a mold cavity configured to define the element's exterior surface in a series of at least three steps, commencing with an initial step. In each step, the material mixture is injected over a predetermined time period at a predetermined velocity and under a predetermined pressure. Each predetermined velocity in the steps following the initial step is less than the predetermined velocity in an immediately preceding step thereof. Each predetermined pressure in the steps following the initial step is less than the predetermined pressure in the immediately preceding step thereof.

Abstract: Low density, buoyant materials, in particular hydrophobic aerogels, may be used to absorb hydrophobic liquids. The materials are adapted to float on aqueous solutions and can absorb oils or other hydrophobic liquids from the surface of the solution without absorbing appreciable amounts of the aqueous solution. Methods for creating and using the materials are disclosed.

Abstract: Disclosed is a polyimide foam made of an aromatic polyimide composed of a tetracarboxylic acid component, which is composed of 0 to 90% by mole of a 3,3?,4,4?-biphenyltetracarboxylic acid component and 100 to 10% by mole of a 3,3?,4,4?-benzophenone tetracarboxylic acid component and/or a 2,3,3?,4?-biphenyltetracarboxylic acid component, and a diamine component, which is composed of 50 to 97% by mole of m-phenylenediamine and 50 to 3% by mole of 4,4?-methylenedianiline. The polyimide foam can be produced easily, has uniform and fine cells, and has the mechanical properties required for practical use as a foam, such as flexibility that prevents the foam from cracking easily even when deformed and excellent cushioning properties, as well as heat resistance that can resist use at high temperatures.

Abstract: The present invention relates to a porous ABPBI (phosphoric acid doped poly(2,5-benzimidazole)) membrane and process of preparing the same. A stable porous ABPBI (Phosphoric Acid Doped Poly(2,5-benzimidazole)) membrane stable to acids, bases, solvents and autoclaving is disclosed. The membrane finds use for separation of solutes in solution in acids, bases and solvents.

Abstract: Provided is a polyamide polymer in which a partial structure represented by the following formula (C) constitutes a portion of the main chain: wherein in Formula (C), RA and RB each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; n and m each independently represent an integer from 0 to 2; Cy represents an unsaturated 6-membered or 7-membered ring which may contain a heteroatom; and * and ** each represent a bonding hand, while * may be a bonding hand extending from RA.

Abstract: A process for the manufacture of a fiber or foil comprising at least one optionally functionalized polymer with a high Tg selected from the group consisting of poly(aryl ether sulfone) (PAES), poly(aryl ether ketone) (PAEK) and aromatic polyimide, comprising the steps of (aa) providing a solution comprising at least 45 wt. % of the polymer, and at least 20 wt. %, of at least one halogen-free organic solvent (S1) for the polymer, both wt % based upon the weight of the solution; (bb) pushing the solution through a nozzle; and (cc) introducing the solution into a coagulation bath comprising: (cc1) at least one liquid (L1) in which the polymer is insoluble, and optionally (cc2) at least one organic solvent (S2) for the polymer, identical to or different from the organic solvent (S1), to form a fiber or foil. A fiber or foil obtained by this process as well as to fibers or foils with specific porosity features and/or mechanical properties.

Abstract: Disclosed are fast-curing, inexpensive corn-gluten resin compositions, methods for making them, methods for forming them into solid articles. In some embodiments, the resin composition includes corn meal gluten and a non-toxic organic acid.

Abstract: An organic aerogel includes a polymer prepared from a substituted or unsubstituted maleimide compound and a compound having at least two vinyl groups. A composition for the organic aerogel includes a substituted or unsubstituted maleimide compound and a compound having at least two vinyl groups.

Abstract: Polycondensates with long-chain linear methylene sequences, their production, a method for producing linear odd-numbered C>20 ?,?-dicarboxylic acids and derivatives thereof and applications of the polycondensates are described.

Abstract: Polyetherimide particles or powders with a high surface area and high porosity can be prepared by precipitation of polymer solution in hot water or steam without the use of any additives. The particles or powders produced rapidly dissolved in organic solvents as well as epoxy matrices.

Abstract: Hybrid spray foams utilize a urethane reactant, a crosslinker, and an (optional) epoxy and/or acrylic resin along with a blowing agent and rheology modifier to produce a quick-setting foam that remains in place until the foam forms and cures. The urethane reactant may be formed as an adduct with or without the use of isocyanate chemistry. In some embodiments, the polyurethane oligomer is made by reacting cyclocarbonates and di- or polyamines, while in other embodiments the polyurethane backbone employs the use of commercially available capped or blocked urethane oligomers made by any method. The oligomers contain reactive groups, typically at the oligomer ends, that crosslink with crosslinkers or with acrylic or epoxy resins to form hybrid polyurethane foams. Foams may also contain a plasticizer, and/or a surfactant as well as other optional additives. Methods of making such foams are also provided.

Abstract: An adsorption-desorption material, in particular, crosslinked vinylepoxide-amine polymeric materials having an Mw from about 500 to about 1×106, a total pore volume from about 0.2 cc/g to about 2.0 cc/g, and an adsorption capacity of at least about 0.2 millimoles adsorbed CO2 per gram of adsorption-desorption material, and linear vinylepoxide-amine polymeric materials having an Mw from about 140 to about 1×106, a total pore volume from about 0.2 cc/g to about 2.0 cc/g, and an adsorption capacity of at least about 0.2 millimoles adsorbed CO2 per gram of adsorption-desorption material. This disclosure also relates to processes for preparing the crosslinked and linear vinylepoxide-amine materials, as well as to selective removal of CO2 and/or other acid gases from a gaseous stream using the vinylepoxide materials.

Abstract: The present disclosure relates to the preparation of ketal compounds from anhydropentitols and oxocarboxylates; derivatives, homopolymers, and copolymers thereof; and various compositions, formulations, and articles derived therefrom.

Abstract: Composite moulded product comprising of at least one polyamide-reinforcement layer consisting of a polyamide matrix and reinforcement fibres, characterised in that the polyamide-reinforcement layer is porous due to the consolidation using a pressurised steam process.

Abstract: A chiral inorganic mesoporous material characterized by having a chiral twisted structure and being mesoporous; a process for producing the material; and a method of using the material. The process for inorganic mesoporous material production is a method in which one or more polymerizable inorganic monomers selected from the group consisting of polymerizable inorganic monomers and polymerizable inorganic monomers having a functional group capable of having a charge are polymerized in the presence of a solvent using as a template a self-assembly of a chiral surfactant such as an N-(higher alkanoyl)amino acid salt. Examples of the use of the inorganic mesoporous material include the separation of racemates and reaction fields for asymmetric syntheses.

Abstract: Fibered particles combine microscale spheroid particles and nanoscale fibers in an integrated body. Fibered particles may be combined with a matrix precursor to form syntactic foams incorporating both particles and fibers.

Abstract: A porous polyimide obtained by removing a silica phase from an organic-inorganic polymer hybrid having a molecule structure in which a polyimide phase and the silica phase are held together by covalent bond.

Abstract: Disclosed is a polyimide foam made of an aromatic polyimide composed of a tetracarboxylic acid component, which is composed of 0 to 90% by mole of a 3,3?,4,4?-biphenyltetracarboxylic acid component and 100 to 10% by mole of a 3,3?,4,4?-benzophenone tetracarboxylic acid component and/or a 2,3,3?,4?-biphenyltetracarboxylic acid component, and a diamine component, which is composed of 50 to 97% by mole of m-phenylenediamine and 50 to 3% by mole of 4,4?-methylenedianiline. The polyimide foam can be produced easily, has uniform and fine cells, and has the mechanical properties required for practical use as a foam, such as flexibility that prevents the foam from cracking easily even when deformed and excellent cushioning properties, as well as heat resistance that can resist use at high temperatures.

Abstract: Disclosed herein are a polyimide-polybenzoxazole copolymer, a method for preparing thereof and a gas separation membrane comprising the same. More specifically, provided are a polyimide-polybenzoxazole copolymer simply prepared through thermal-rearrangement performed by thermally treating a polyimide-poly (hydroxyimide) copolymer as a precursor, a method for preparing the same, and a gas separation membrane comprising the same. The copolymer shows superior gas permeability and gas selectivity, thus being suitable for use in gas separation membranes in various forms such as films, fibers or hollow fibers. The gas separation membrane thus prepared can advantageously endure even harsh conditions such as long operation time acidic conditions and high humidity due to the rigid polymer backbone present in the copolymer.

Abstract: A polyimide foam formed of an aromatic polyimide prepared from a 3,3?,4,4?-biphenyltetracarboxylic acid component and an aromatic diamine component. The polyimide foam has flexibility at least such that no cracking occurs when a specimen of the polyimide foam with a 1 cm by 1 cm cross-section and a length of 5 cm is deformed until both ends thereof come into contact with each other to make a closed loop. The polyimide foam is obtained by dissolving a 3,3?,4,4?-biphenyltetracarboxylic acid component and an aromatic diamine component in a solvent in the presence of an acid phosphoric ester having a specific structure to prepare a polyimide precursor and heating the polyimide precursor to expand.

Abstract: In order to make available polymer compounds that are improved with respect to their properties compared to conventional PTFE, on the one hand, and the further high-performance polymer or polymers, on the other, it is proposed that a polymer compound has a proportion of a fully fluorinated thermoplastic polymer material as well as a proportion of at least one further high-performance polymer different therefrom, selected from the group of polyphenylene sulphide (PPS), polyphenylene sulphone (PPSO2), polyamide (PA), polyimide (PI), polyamide-imide (PAD, and polyether imide (PEI) as well as copolymers and derivatives of these polymers and copolymers, wherein the compound has a homogeneous distribution of the proportions of the polymers and the polymer material.

Abstract: The invention involves composite materials containing a polymer foam and an aerogel. The composite materials have improved thermal insulation ability, good acoustic insulation, and excellent physical mechanical properties. The composite materials can be used, for instance, for heat and acoustic insulation on aircraft, spacecraft, and maritime ships in place of currently used foam panels and other foam products. The materials of the invention can also be used in building construction with their combination of light weight, strength, elasticity, ability to be formed into desired shapes, and superior thermal and acoustic insulation power. The materials have also been found to have utility for storage of cryogens. A cryogenic liquid or gas, such as N2 or H2, adsorbs to the surfaces in aerogel particles. Thus, another embodiment of the invention provides a storage vessel for a cryogen.

Abstract: Porous spherical particles of polyamide 11 or polyamide 12 can be produced by an industrially advantageous process which comprises the steps of mixing a polyamide solution of polyamide 11 or polyamide 12 dissolved in a phenol compound and a low molecular weight aliphatic alcohol which is a poor solvent for the polyamides but is well compatible with the phenol compound in the presence of a high molecular weight alkylene glycol to prepare a mixture solution having an initial viscosity of 10 mPa·s or more, and allowing the mixture solution to stand, to precipitate polyamide particles.

Abstract: Process for preparation of high-molecular-weight polyamides, which comprises reacting a polyamide A) at a temperature of from 150 to 350° C. with a compound B) which at this reaction temperature liberates isocyanic acid, where the concentration of the amino end groups in the polyamide A) used is greater than or equal to the concentration of the carboxy end groups.

Abstract: A porous material is provided which comprises a transparent polymer matrix defining interconnected pores and a wetting agent. At least a portion of the wetting agent is cross-linked with the polymer matrix. A process for forming a porous polymeric material is also provided. A bicontinuous microemulsion comprising water, a wetting agent, a monomer, and a surfactant copolymerizable with the monomer is polymerized, to form a polymer defining interconnected pores. The wetting agent comprises a cross-linkable wetting agent such that after polymerization, at least a portion of the cross-linkable wetting agent is cross-linked with the polymer. The wetting agent may comprise acrylated hyaluronic acid (AHA) such as methacrylated hyaluronic acid (MeHA). The wetting agent may also comprise a hyaluronic acid (HA). The wetting agent may include an unbonded portion that this releasable from the material. A contact lens may be made from the porous material.

Abstract: Polyetherimide foam materials, articles that include these foam materials and methods of making these foam materials and articles. The foam extrusion process uses selected blowing agents, equipment design and processing conditions to produce continuously extruded foam with a substantially uniform cell size in a lower density PEI foam, such as 25 to 50 g/L or a higher density PEI foam, such as 120 to 300 g/L. Due to the greater densities that can be produced as well as the characteristics inherent in polyetherimide articles, the resulting foam materials are suitable for a much broader range of applications.

Abstract: Organic, small pore area materials (“SPMs”) are provided comprising open cell foams in unlimited sizes and shapes. These SPMs exhibit minimal shrinkage and cracking. Processes for preparing SPMs are also provided that do not require supercritical extraction. These processes comprise sol-gel polymerization of a hydroxylated aromatic in the presence of at least one suitable electrophilic linking agent and at least one suitable solvent capable of strengthening the sol-gel. Also disclosed are the carbonized derivatives of the organic SPMs.

Abstract: Provided are a composition for forming film which can form porous film excelling in dielectric constant, adhesiveness, uniformity of the film, mechanical strength and having low hygroscopicity; porous film and a method for forming the film; and a high-performing and highly reliable semiconductor device comprising the porous film inside. More specifically, provided is a composition for forming porous film, the composition comprising siloxane polymer and one or more quaternary ammonium salts represented by following formula (1) or (2): [(R1)4N]+[R2X]???(1) Hk[(R1)4N]m+YV???(2) wherein X represents CO2, OSO3 or SO3; Y represents SO4, SO3, CO3, O2C—CO2, NO3 or NO2; and k is 0 or 1, m is 1 or 2 and n is 1 or 2 in proviso that n=1 requires k=0 and m=1, and n=2 requires k=0 and m=2, or k=1 and m=1.

Abstract: A preparation process of polyimide aerogels that composed of aromatic dianhydrides and aromatic diamines or a combined aromatic and aliphatic diamines is described. Also descried is a process to produce carbon aerogels derived from polyimide aerogel composed of a rigid aromatic diamine and an aromatic dianhydride. Finally, the processes to produce carbon aerogels or xerogel-aerogel hybrid, both of which impregnated with highly dispersed transition metal clusters, and metal carbide aerogels, deriving from the polyimide aerogels composed of a rigid aromatic diamine and an aromatic dianhydride, are described. The polyimide aerogels and the polyimide aerogel derivatives consist of interconnecting mesopores with average pore size at 10 to 30 nm and a mono-dispersed pore size distribution. The gel density could be as low as 0.008 g/cc and accessible surface area as high as 1300 m2/g.

Abstract: A flexible polyimide foam having an apparent density of 13.5 to 900 kg/m3 and a glass transition temperature of 300° C. or higher can be prepared by mixing an aromatic tetracarboxylic acid comprising 2,3,3′,4′-biphenyltetracarboxylic dianhydride a portion of which is converted into its mono- or di-lower primary alcohol ester with an aromatic polyamine containing diaminodisiloxane in an amount of 0.1 to 10 mol. %, based on the amount of total amine compounds, to give a solid of polyimide precursor; heating the solid of polyimide precursor to a temperature of 300° C. to 500° C. to produce a polyimide foam; and compressing the polyimide foam.

Abstract: Performance additives in high performance polymers using polyhedral oligomeric silsesquioxanes (POSS) and polyhedral oligomeric silicates (POS) as nanoscopic reinforcements, porosity control agents, thermal and oxidative stability aids to improve the properties of the polymers.

Abstract: A flexible polyimide foam having an apparent density of 70 kg/m3 or less and a glass transition temperature of 300° C. or higher can be prepared by mixing an aromatic tetracarboxylic acid comprising 2,3,3′,4′-biphenyltetracarboxylic dianhydride a portion of which is converted into its mono- or di-lower primary alcohol ester with an aromatic polyamine containing diaminodisiloxane in an amount of 0.1 to 10 mol. %, based on the amount of total amine compounds, to give a solid of polyimide precursor; and heating the solid of polyimide precursor to a temperature of 300° C. to 500° C.

Abstract: A polyimide porous film obtained by drying and imidizing a polyimide precursor porous film which is substantially homogeneous on both sides, the polyimide porous film having pores on both sides wherein the pores all satisfy the conditions: 1) the difference in the mean pore size of both sides is less than 200% based on the smaller average value of the mean pore size, 2) the coefficient of variation for the pore size on each side is smaller than 70%, 3) the coefficient of variation for the pore centroid distance on each side is smaller than 50%, and 4) the mean pore size on each side is 0.05-5 &mgr;m.

Abstract: Microcellular rigid foams with a matrix consisting of cross-linked duromers, especially of polytriazine resins, and with an apparent density of 20 to 95 percent of the density of the compact matrix material. The rigid foams are highly stable and highly temperature resistant and are suitable for use, e.g., as material for aircraft lining.

Abstract: A water-swellable polymer gel prepared by reacting an ester of a carboxyl group-containing polysaccharide with a compound having at least two &agr;-amino groups, which is derived from a natural amino acid, and a foamed article thereof. The water-swellable polymer gel can be used in the fields such as industry, agriculture, food and medicine. The applications of the water-swellable gel in the medical field include wound dressings, adhesion-preventing materials, dialysis membranes, hemostatic materials, adhesive materials, sealants, contact lenses, materials for tissue regeneration, microcapsule materials and drug delivery systems.

Abstract: Superabsorbent fiber and film compositions comprising partially acidified, hydrolyzed, internally plasticized, crosslinked, superabsorbing fibers or film derived from polysuccinimide and processes for preparing same.

Abstract: A porous material made of a dry gel of a polyimide resin having an apparent density of 800 kg/m3 or less and a mean pore size of 1 &mgr;m or less is disclosed. The porous material exhibits high heat resistance and is low in density and mean pore size. The use of the porous material provided by the present invention can produce not only a heat insulator with a low thermal conductivity and high heat insulation but also an insulating material having a low dielectric constant and exhibiting excellent dielectric characteristics at high frequencies. The present invention can also provide a semiconductor circuit including the insulating material.

Abstract: Porous polyimide dielectric materials having low dielectric constants useful in electronic component manufacture are disclosed along with methods of preparing the porous polyimide dielectric materials. Also disclosed are methods of forming integrated circuits containing such porous polyimide dielectric material.

Abstract: The present invention provides a material for electrical insulating organic film, superior in electrical properties, thermal properties and low water absorption; an electrical insulating organic film made from the material; and a process for production of the film. That is, the present invention provides an electrical insulating organic film having fine pores, consisting of a layer of a polybenzoxazole resin represented by the following general formula (1): wherein n is an integer of 2 to 1,000; X is a tetravalent organic group; and Y is a bivalent organic group; a material for electrical insulating organic film obtained by mixing a polybenzoxazole precursor or a polybenzoxazole resin, with an oligomer; and a material for electrical insulating organic film, obtained by reacting at least one carboxylic acid terminal of a polybenzoxazole precursor with an amino group- or hydroxyl group-containing oligomer.

Abstract: A porous polyimide having a finely cellular structure and having a low dielectric constant and heat resistance. The porous polyimide can be produced by a process comprising adding a dispersible compound to a polyimide precursor to form a micro-domain structure in which the dispersible compound is dispersed in the polymer so as to have a size smaller than 10 &mgr;m and then removing the dispersible compound by extraction with supercritical carbon dioxide to thereby make the precursor porous, wherein the interaction parameter &khgr;AB between the polyimide precursor A and the dispersible compound B is larger than 3. This porous polyimide has an average cell diameter smaller than 5 &mgr;m and a dielectric constant of 3 or lower.

Abstract: A novel dielectric composition is provided that is useful in the manufacture of electronic devices such as integrated circuit devices and integrated circuit packaging devices. The dielectric composition is prepared by crosslinking a thermally decomposable porogen to a host polymer via a coupling agent, followed by heating to a temperature suitable to decompose the porogen. The porous materials that result have dielectric constants less than about 3.0, with some materials having dielectric constants less than about 2.5. Integrated circuit devices, integrated circuit packaging devices, and methods of manufacture are provided as well.

Abstract: Nanoporous materials are fabricated from polymers having backbones with reactive groups used in crosslinking. In one aspect of preferred methods and compositions, the reactive groups in the backbone comprise a diene and a dienophile. The diene may advantageously comprise a tetracyclone, and the dienophile may advantageously comprise an ethynyl. In another aspect of preferred methods and compositions, the reactive groups in the backbone are included in a conjugated system. Especially preferred polymeric strands comprise a poly(arylene ether) synthesized from a difluoroaromatic portion and an aromatic bisphenolic portion. It is still more preferred that the difluoroaromatic portions of the poly(arylene ether) are modified in such a way that some difluoroaromatic portions carry a thermolabile portion. In still other aspects crosslinking may advantageously occur without reliance on an exogenous crosslinker.

Abstract: Superabsorbent fiber and film compositions comprising partially acidified, hydrolyzed, internally plasticized, crosslinked, superabsorbing fibers or film derived from polysuccinimide and processes for preparing same.

Abstract: In the present invention, an inorganic reactant is, or reactants are, localized with respect to a dendritic polymer by physical constraint within or by a non-covalent conjugation to the dendritic polymer. The localized inorganic reactant or reactants is/are subsequently transformed to form a reaction product which is immobilized with respect to the dendritic polymer. This immobilization occurs on a nanoscopic scale as a consequence of the combined effects of structural, chemical and physical changes without having covalent bonds between the product(s) and the dendritic container and results in new compositions of matter called dendritic nanocomposites. The resulting nanocomposite material can be used to produce revolutionary products such as water soluble elemental metals, with specific applications including magnetic resonance imaging, catalytic, magnetic, optical, photolytic and electroactive applications.

Abstract: A shaped article composed of an aromatic polyimide has a hollow, essentially spherical structure and a particle size of about 100 to about 1500 &mgr;m, a density of about 1 to about 6 pounds/ft3 and a volume change of 1 to about 20% by a pressure treatment of 30 psi for 10 minutes at room temperature. A syntactic foam, made of a multiplicity of the shaped articles which are bonded together by a matrix resin to form an integral composite structure, has a density of about 3 to about 30 pounds/ft3 and a compression strength of about 100 to about 1400 pounds/in2.

Abstract: Nanoporous polymeric materials are fabricated in which polymeric strands are crosslinked via ring structures. Preferred ring structures are formed de novo during crosslinking, and at least some of the ring structures are preferably included in the backbones of the strands. At least one of the ring structures may advantageously comprise an aromatic structure, and may more advantageously comprise a benzyl moiety. Especially preferred polymers comprise a poly(arylene ether) synthesized from a difluoroaromatic portion and an aromatic bisphenolic portion. In another preferred aspect, the difluoroaromatic portions of the poly(arylene ether) carry at least two different crosslinking functionalities. In an even more preferred aspect, the crosslinking functionalities comprise an ethynyl and a tetracyclone. Nanoporosity is preferably introduced by thermolyzing one or more thermolabile portions in the crosslinked polymer. An especially preferred thermolabile portion comprises ethylene glycol-poly(caprolactone).

Abstract: Compositions and methods are provided in which nanoporous polymeric materials are produced via stable, polymeric template strands having reactive groups that can be used for forming crosslinking functionalities and/or adding thermolabile groups, wherein at least some of the thermolabile groups are thermolyzed to produce voids. The template strands preferably comprise aromatic systems and vicinal keto groups, such as a polybenzil formed from fluorene bisphenol or 3,3'-dihydroxytolane with 4,4'-difluorobenzil. At least some of the reactive groups preferably react using an addition-elimination reaction. Especially preferred thermolabile groups comprise poly(propylene oxide), and especially preferred crosslinkers comprise ethynyl-moiety and tetracyclone moieties.

Abstract: A silicate-based blowing agent and method for producing foamed polymers provides a blowing agent containing at least one metal silicate, boric acid or a salt thereof, a peroxy compound, a reaction initiator and, optionally, a desiccant. The blowing agent is prepared by mixing the ingredients at least one time and allowing the mixture to rest without mixing until a dry dilatent gel is formed. The blowing agent is useful for the production of foamed polymers, especially for the production of foamed rubber.

Abstract: A shaped article composed of an aromatic polyimide has a hollow, essentially spherical structure and a particle size of about 100 to about 1500 .mu.m, a density of about 1 to about 6 pounds/ft.sup.3 and a volume change of 1 to about 20% by a pressure treatment of 30 psi for 10 minutes at room temperature. A syntactic foam, made of a multiplicity of the shaped articles which are bonded together by a matrix resin to form an integral composite structure, has a density of about 3 to about 30 pounds/ft.sup.3 and a compression strength of about 100 to about 1400 pounds/in.sup.2.

Abstract: A method of preparing polyimide foam produces a foam with excellent flexibility properties. The method of preparing polyimide foam is performed by foaming polyimide percursor which is prepared by employing linear aliphatic diamine and aromatic diamine containing 4 to 12 carbon atoms, at specific weight ration into the esterified reaction mixture prepared by reacting an aromatic carboxylic acid or its anhydride with excess amount of an alcohol compound. The polyimide foam produced by the method described retins superior characteristics of conventional polyimide foams and in addition have excellent flexibility so that it is used widely as adiabatic material, acoustical absorbent and cushion material in the aerospace industry, submarine and express trains etc.