The invention generally relates to polymer nanocomposite films that possess shape memory properties at elevated temperatures. Such films can absorb microwaves, are thermally conductive, are electrically conductive and have increased mechanical strength. In addition, the present invention relates to methods of fabricating such films into 3D objects. Due to the improved properties of such films more advanced sensors and microwave shields can be constructed.

A diamine monomer compound with a structural formula of

##STR00001##

wherein n.sub.1 is an integer greater than 1, forms the basis of a dielectric material with reduced dielectric losses for improved signals transmission. A method for preparing the compound, a polyimide resin made from the compound, a flexible film, and an electronic device including the polyimide resin are also disclosed. The compound has a long but flexible even numbered carbon chain and a liquid crystal unit structure. The reduced regularity and rigidity of the molecular chain make the polyimide resin convenient for film-forming. Dimensional stability is improved, the coefficient of thermal expansion of the materials is reduced, and the materials have good mechanical and thermal properties, the electron loss factor and coefficient of thermal expansion of the materials being reduced.

A polyimide precursor includes a repeating unit of formulae (I) and (II):

##STR00001## where R1 and R3 are each a tetravalent group of a tetracarboxylic dianhydride residue, and R2 and R4 are respectively a divalent group of a residue of a first-type diamine and a divalent group of a residue of a second-type diamine. The first-type diamine is represented by formula (III), and the second-type diamine is represented by formula (IV). A resin composition including the polyimide precursor, a polyimide formed from the polyimide precursor, and use of the polyimide are also disclosed.

A polyimide precursor solution includes an aqueous solvent including water, a polyimide precursor, resin particles, and an ionization agent X having a boiling point of 100° C. or more and 130° C. or less and an ionization agent Y having a boiling point of 250° C. or more and 300° C. or less.

The invention relates to a process of manufacturing a composite comprising a layer of a polyimide and a substrate, comprising at least these steps: i. Providing a first composition comprising an acid compound; and a second composition comprising a diamine compound; ii. Forming a first layer on the substrate, and iii. Forming a second layer on the first layer, wherein if the first layer is formed by applying the first composition, the second layer is formed by applying the second composition, and vice versa; wherein the first and the second layer overlap at least in part thereby forming a pattern on the substrate; iv. Conducting a thermal treatment on the pattern wherein the polyimide layer is formed. The invention further relates to such a composite, a kit comprising a first composition comprising an acid compound and a second composition comprising a diamine compound as well as a use of the kit.

A process for preparing a polyamide-imide (PAI) polymer is provided. The process comprises the melt polymerization of a reaction mixture comprising at least one cycloaliphatic acid component comprising three carboxyl moieties, the carboxyl moieties selected from the group consisting of carboxylic acid, acid anhydride and ester functional groups, and at least one diamine component. The process comprises maintaining the reaction mixture in a liquid state and at a temperature of at least 200° C. during polymerization.

The present invention employs a polyimide film, which has a coefficient of thermal expansion (CTE) that is a negative number at a temperature equal to or greater than 350° C., as a debonding layer for separating a flexible substrate and a carrier substrate, and thus can easily separate a flexible substrate from a carrier substrate by using a detaching phenomenon caused by a difference in residual stress between the flexible substrate and the debonding layer after a high-temperature process for producing an element on the flexible substrate. Therefore, the present invention can separate the flexible substrate without causing chemical or physical damage to the element formed on the flexible substrate, thereby minimizing problems that may occur during a stripping process.

Provided is a polyimide precursor including a polyimide precursor obtained by a reaction between a diamine compound and a tetracarboxylic dianhydride compound, in which the diamine compound contains at least one type selected from the group consisting of an aromatic diamine and an alicyclic diamine, the tetracarboxylic dianhydride compound contains at least one type selected from the group consisting of an aromatic tetracarboxylic dianhydride and an alicyclic tetracarboxylic dianhydride, and the total amount of the alicyclic diamine and the alicyclic tetracarboxylic dianhydride is 5.0 mol% or more and 70.0 mol% or less with respect to the total amount of constituent monomers of the polyimide precursor.

A method of making diimide and dianhydride that includes contacting a nitro or halo N-substituted phthalimide with bisphenol in polar aprotic solvents, such as dimethylsulfoxide and sodium hydride to provide high conversion to a diimide; precipitating the product in acetic acid solution and filtration; treating the resulting solid, N-substituted diimide with a carboxylic acid and substituted or unsubstituted dimethyl sulfoxide in an aqueous medium to provide a reaction mixture including tetra acid, triacid, imide diacid and diimide along with substituted or unsubstituted acetic acid, dimethyl sulfoxide and their derivatives. The method includes the isolation of tetra acid by precipitation in water followed by centrifuge or filtration. The tetra acid is converted into the corresponding dianhydride. The dianhydride prepared by the method are also described as precursor to make polyetherimide.

A method of making a three-dimensional object comprising one or more polyimide copolymers, polyimide composites or combinations thereof is provided. The method involves 3D printing a solution comprising polyamic acid (PAA), tetraethyl orthosilicate (TEOS), and a silane selected from the group consisting of aminopropyl trimethoxysilane (APTMS), aminopropyl triethoxysilane (APTES), N-[3-(trimethoxysilyl)propyl]-ethylene diamine (ETDA), and glycidoxypropyl trimethoxysilane (GPTMS) to produce a three-dimensional form, and thermosetting the three-dimensional form.