The present invention relates to a novel acid dianhydride, a method for preparing the same, and a polyimide prepared therefrom. More specifically, the acid dianhydride according to the present invention is useful as a colorless transparent polyimide unit exhibiting excellent thermal stability and a low dielectric ratio, and the polyimide of the present invention has excellent solubility to an organic solvent compared with the conventional polyimide.

The present invention provides a method for producing a polyimide resin powder, including the step of reacting (A) a tetracarboxylic acid component containing a tetracarboxylic dianhydride with (B) a diamine component containing an aliphatic diamine in the presence of (C) a solvent containing an alkylene glycol-based solvent represented by the formula (1): ##STR00001##
wherein Ra.sub.1 represents a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, Ra.sub.2 represents a linear alkylene group having from 2 to 6 carbon atoms, and n represents an integer of 1-3.

The present invention relates to a novel acid dianhydride, a method for preparing the same, and a polyimide prepared therefrom. More specifically, the acid dianhydride according to the present invention is useful as a colorless transparent polyimide unit exhibiting excellent thermal stability and a low dielectric ratio, and the polyimide of the present invention has excellent solubility to an organic solvent compared with the conventional polyimide.

A poly(imide-amide) copolymer, which is a product of a reaction between a diamine including an amide structural unit-containing oligomer represented by Chemical Formula 1 and a dianhydride represented by Chemical Formula 3:

##STR00001## wherein, groups and variables in Chemical Formulae 1 and 3 are the same as described in the specification.

A method for using citraconic anhydride and itaconic anhydride as addition cure end caps in reactions for forming polyamic acid oligomers and polyimide oligomers, is provided. Prepregs and high temperature adhesives made from the resulting oligomers, as well as, high temperature, low void volume composites made from the prepregs, are also provided.

A poly(imide-amide) copolymer includes: an imide structural unit which is a reaction product of a first diamine and a dianhydride, and an amide structural unit which is a reaction product of a second diamine and a diacyl halide, wherein each of the first diamine and the second diamine includes 2,2-bis-trifluoromethyl-4,4-biphenyldiamine, and at least one of the first diamine and the second diamine further includes a compound represented by Chemical Formula 1, wherein the dianhydride includes 3,3,4,4-biphenyltetracarboxylic dianhydride and 4,4-hexafluoroisopropylidene diphthalic anhydride, wherein the diacyl halide includes terephthaloyl chloride (TPCI), and wherein an amount of the compound represented by Chemical Formula 1 is less than or equal to about 10 mole percent based on the total amount of the first diamine and the second diamine:

NH.sub.2-A-NH.sub.2Chemical Formula 1 wherein in Chemical Formula 1, A is the same as described in the detailed description.

A polyimide polymer represented by the following formula 1 is provided.

##STR00001##

In formula 1, Ar is

##STR00002##

Ar is

##STR00003##

A is

##STR00004##

and 0<X<0.38.

A polyimide, comprising 1-100 mol % of repeating units of formula (1), based on 100 mol % of total repeating units of the polyimide, wherein each V is as defined herein; and each R.sup.1 is independently a divalent group of formula (3), wherein A is anionic, and each A is independently O, S, S(O).sub.2, S(O).sub.2O, OS(O).sub.2O, OP(O) (OR).sup.dO, P(O)(R.sup.e)O, P(O)(OR.sup.f)O, or OP(O)(R.sup.g)O; and X is cationic, and each X is independently Li, Na, K, Cs, Mg, Ca, Sr, Cr, Mn, Fe, Co, Ni, Cu, Ag, Zn, Cd, B, Al, Ga, In, Ge, Sn, Pb, As, Sb, phosphonium, imidazolium, guanidinium, or pyridinium; and R.sup.d, R.sup.e, R.sup.f, and R.sup.g are each independently hydrogen, substituted or unsubstituted C.sub.1-8 alkyl, or substituted or unsubstituted C.sub.6-12 aryl.

Laser fabricated graphene fiber which can be prepared from a fluorinated polyimide fiber is disclosed. The graphene fiber exhibits an ultrahigh specific surface area, facilitating excellent electrochemical properties, useful for example in tranducers, capacitors, and micro-supercapacitors.

A polyimide precursor resin composition for forming a flexible device substrate, including a polyamic acid having a structure obtained from a tetracarboxylic acid component including at least one of 3,3,4,4-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, a diamine component including at least one of paraphenylene diamine and 4,4-diaminodiphenyl ether, and a carboxylic acid monoanhydride, the polyamic acid satisfying equations (1) and (2) below:
0.97X/Y<1.00Equation (1)
0.5(Z/2)/(YX)1.05Equation (2)
in which X represents a number of moles of tetracarboxylic acid component, Y represents a number of moles of diamine component, and Z represents a number of moles of the carboxylic acid monoanhydride.