Abstract: Disclosed is a method for producing a circuit structure having an insulator layer comprising a porous silicon oxide thin film, which comprises (1) forming a preliminary insulator layer comprising a silicon oxide-organic polymer composite thin film formed on a substrate, which silicon oxide-organic polymer composite thin film comprises a silicon oxide having an organic polymer dispersed therein, (2) forming, in the preliminary insulator layer, a groove which defines a pattern for a circuit, (3) forming, in the groove, a metal layer which functions as a circuit, and (4) removing the organic polymer from the preliminary insulator layer to render the preliminary insulator layer porous, thereby converting the preliminary insulator layer to an insulator layer comprising a porous silicon oxide thin film. By the method of the present invention, the capacitance between mutually adjacent circuit lines (line-to-line capacitance) in the circuit structure can be lowered.

Abstract: Disclosed is an alkoxysilane/organic polymer composition for use in producing an insulating thin film, comprising (A) a specific alkoxysilane; (B) a specific organic polymer; and (C) a solvent for alkoxysilane (A) and organic polymer (B), wherein solvent (C) comprises at least one organic solvent selected from the group consisting of amide linkage-containing organic solvents and ester linkage-containing organic solvents. Also disclosed are a silica-organic polymer composite thin film which is produced by a process comprising: forming a thin film of the composition of the present invention; subjecting the thin film to a hydrolysis and dehydration-condensation reaction with respect to the alkoxysilane thereof, to thereby cause the alkoxysilane to be gelled in the thin film; and removing the solvent remaining in the thin film by drying, and a porous silica thin film which is obtained by removing the organic polymer from the silica-organic polymer composite thin film.

Abstract: Disclosed is an aromatic copolymer comprising a plurality of aromatic copolymer chains, each comprising (A) recurring 2,6-diphenylphenol units and (B) phenolic comonomer units, each comonomer unit being independently selected from the group consisting of (i) an oxyphenylene monomer unit which is monosubstituted with a monovalent aromatic group or a halogen atom, (ii) an &agr;-oxynaphthylene monomer unit, (iii) a &bgr;-oxynaphthylene monomer unit, and (iv) an oxyphenylene monomer unit which is substituted with at least one aliphatic group, wherein the amounts of (A) and (B) are from 50 to 98% by weight and from 2 to 50% by weight, based on the weight of the aromatic copolymer, provided that, when (iv) is present as the comonomer unit, the amount of (iv) is 20% by weight or less, based on the weight of (B), and wherein the aromatic copolymer has a weight average molecular weight of from 1,000 to 3,000,000. A method for producing the aromatic copolymer is also disclosed.

Abstract: There are disclosed dibenzofuran amorphous polymer comprising a recurring unit represented by following formula (II) and having a molecular weight giving a reduced viscosity of at least 0.2 dl/g as measured in the form of a 0.5% (W/V) solution in N-methyl-pyrrolidone at 25.degree. C., a process for producing said amorphous polymer, a dibenzofuran copolymer comprising, in addition to a recurring unit represented by following formula (II), at least one type of recurring unit represented by following general formula (III) in a specific proportion and having a molecular weight giving a reduced viscosity of at least 0.2 dl/g as measured in the form of a 0.5% (W/V) solution in concentrated sulfuric acid at 25.degree. C., and a process for producing said copolymer. ##STR1## wherein A is --O--, --CO--, --S--, --SO.sub.2 --, a divalent alkylene group or a single bond and n is a number of 0, 1 or 2.

Abstract: There are disclosed a process for producing an aromatic (poly)etherketone or an aromatic (poly)ethersulfone having an ether group represented by the formula --Y--Ar--O--Ar--Y-- which process comprises reacting an aromatic halogen compound having at least one active halogen group represented by the formula --Y--Ar--X, where Y denotes a ketone group or a sulfone group; Ar denotes a phenylene group or a nuclear-substituted product thereof; and X denotes a halogen atom which is bonded at the ortho- or para-position relative to Y, with a specified salt of an alkali metal, and an aromatic polyetherketone polymer which has a repeating unit represented by formula (I) ##STR1## and which has a crystalline melting point not lower than 390.degree. C. and an intrinsic viscosity of 0.7 to 2.0 dl/g (sulfuric acid at 25.degree. C.).

Abstract: A process for preparing a crystalline aromatic polyetherketone having a reduced viscosity of 0.6 or more is disclosed. The process includes polycondensing an aromatic dihydroxy compound with a dihalogeno aromatic ketone in a solvent having the following general formula (I) or (II): ##STR1## wherein each of R.sub.1, R.sub.2 and R.sub.3 is independently a hydrogen atom, a C.sub.1-3 alkyl group or a phenyl group; X is an oxygen atom, a sulfur atom or a direct bond; Y is an oxygen atom or a ketone group; and n is 0 or 1;in the presence of an alkali compound.

Abstract: An acrylonitrile polymer film comprising at least 85 wt. % of acrylonitrile, wherein the difference in the value of the second moment of the broad-line NMR spectrum at 20.degree. C. between the film and the starting polymer powder thereof, or the polymer powder formed by dissolving the film and then precipitating the polymer from the solution, is at least 0.3 Gauss.sup.2 and the infrared dichroic ratio of the nitrile groups satisfies the requirements that 0.4<Ax/Az<0.8, 0.4<Ay/Az<0.8, and 0.8<Ax/Ay<1.25, where Ax and Ay are the absorption intensities of polarized infrared rays oscillating in respective directions parallel to the surface of the film and perpendicular to each other, and Az is the absorption intensity of polarized infrared rays oscillating in the direction perpendicular to the film surface.