Abstract: The invention relates to a process for crosslinking aromatic polymers containing radiation-sensitive methylene groups (--CH.sub.2 --) by exposing the polymers to ionizing radiation thereby causing crosslinking of the polymers through the methylene groups. Crosslinked polymers are resistant to most organic solvents such as acetone, alcohols, hydrocarbons, methylene, chloride, chloroform, and other halogenated hydrocarbon, to common fuels and to hydraulic fluids in contrast to readily soluble uncrosslinked polymers. In addition, the degree of crosslinking of the polymers depends upon the percentage of the connecting groups which are methylene which ranges from 5 to 50% and preferably from 25 to 50% of the connecting groups and is also controlled by the level of irradiation which ranges from 25 to 1000 Mrads and preferably from 25 to 250 Mrads. The temperature of the reaction conditions ranges from 25.degree. to 200.degree. C. and preferably at or slightly above the glass transition temperature of the polymer.

Abstract: A polyether graft copolymer with improved solvent resistance and crystalline thermally reversible crosslinks. The copolymer is prepared by a novel process of anionic copolymerization. Polymers formed in this manner have good solvent resistance and are well suited for commercial aircraft parts.

Abstract: This invention relates to a process using a Diels-Alder reaction which increases the molecular weight and/or crosslinks polymers by reacting the polymers with bisunsaturated dienophiles. The polymer comprises at least 75% by weight based on the reaction product, has a molecular weight of at least 5000 and a plurality of conjugated 1,3-diene systems incorporated into the molecular structure. A dienophile reaction with the conjugated 1,3-diene of the polymer is at least 1% by weight based on the reaction product. Examples of the polymer include polyesters, polyamides, polyethers, polysulfones and copolymers thereof. The bisunsaturated dienophiles may include bis-maleimide, bisnadimides, bis maleic and bis tumaric esters and amides. The method of this invention for expanding the molecular weight chains of the polymers, preferably thermoplastics, is advantageous for processing or fabricating thermoplastics.

Abstract: A method of preparing insoluble thermoplastic aromatic polyimides having uniquely low softening temperatures by reacting, in a suitable solvent, an aromatic dianhydride and a meta-substituted aromatic diamine.

Abstract: A process of preparing aromatic polyamide-acids for use as adhesives by reacting an aromatic dianhydride to an approximately equimolar amount of an aromatic diamine in a water or lower alkanol miscible ether solvent and wherein the polyamide-acids are converted to polyimides by heating to the temperature range of 200.degree. - 300.degree. C. and wherein the polyimides are thermally stable and insoluble in ethers and other organic solvents.