WO2021113489A1

WO2021113489A1 - Polyamic acid varnish from high purity bisphenol a dianhydride and articles prepared therefrom

Info

Publication number: WO2021113489A1
Application number: PCT/US2020/063078
Authority: WO
Inventors: Lucas Robert BUFALINI
Original assignee: Shpp Global Technologies B.V.
Priority date: 2019-12-03
Filing date: 2020-12-03
Publication date: 2021-06-10

Abstract

A varnish composition, comprising a polyamic acid comprising structural units derived from reaction of 5,5'-[1-methylethylidene)bis(4,1-phenyleneoxy)bis-1,3-isobenzofurandione composition with organic diamine; and a solvent, wherein the 5,5'-[1-methylethylidene)bis(4,1-phenyleneoxy)bis-1,3-isobenzofurandione comprises the 5,5'-[1-methylethylidene)bis(4,1-phenyleneoxy)bis-1,3-isobenzofurandione; 25 ppm or less each of sodium, potassium, calcium, zinc, aluminum, titanium, iron, chromium, molybdenum, nickel, and phosphorus ions; 50 ppm or less each of phosphate, sulfate, chloride, nitrate, and nitrite ions; 0.0001 to 10 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 10 wt% of residual 4,4'-BPA diacid; and 0.00001 to 4 wt% of residual 4,4'-BPA imide-anhydride, wherein the dynamic viscosity of the varnish composition is 30,000-120,000 cP at 25°C, and a cured product of the varnish composition has a T_g of 150-300°C, preferably wherein the 5,5'-[1-methylethylidene)bis(4,1-phenyleneoxy)bis-1,3-isobenzofurandione composition comprises greater than or equal to 99 wt% of the 5,5'-[1-methylethylidene)bis(4,1-phenyleneoxy)bis-1,3-isobenzofurandione.

Description

POLYAMIC ACID VARNISH FROM HIGH PURITY BISPHENOL A DIANHYDRIDE AND

ARTICLES PREPARED THEREFROM

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to European Application No.

EP19213248.8 filed on December 3, 2019, the entire content of which is incorporated by reference herein.

BACKGROUND

[0001] Polyimides (PI), and in particular, polyetherimide (PEI), are high performance polymers having a high glass transition temperature (T_g) depending on the monomers used to prepare the polymers. These polymers further have high strength, heat resistance, and modulus, and broad chemical resistance. PEIs are widely used in applications as diverse as automotive and electrical/electronic applications since these compositions offer good mechanical, electrical, and thermal properties.

[0002] PEIs, as well as copolymers thereof, have shown versatility in various manufacturing processes, proving amenable to techniques including injection molding, extrusion, and thermoforming, to prepare various articles including layers, fibers, and composite materials.

[0003] PEIs can be prepared by condensation polymerization, for example of a dianhydride with a diamine. In order to obtain good reaction kinetics, achieve high molecular weight, and provide a stable, processable polymer product, high purity monomer components are desirable. Additionally, some applications can require that the polymers have good optical clarity, and good thermal and mechanical properties.

[0004] There remains a continuing need for new articles, for example including PEI derived from high purity dianhydride monomers, in applications such as varnishes, laminates, adhesives, coatings, and composites.

BRIEF DESCRIPTION

[0005] Provided is a varnish composition comprising a polyamic acid comprising structural units derived from reaction of 5,5'-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: 25 ppm or less, or 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions;

50 ppm or less, or 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions; 0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of residual 4,4'- BPA tetraacid; 0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of residual 4,4'-BPA diacid; and 0.00001 to 4 wt%, or 0.01 to 4 wt%, or 0.01 to 2 wt%, or 0.05 to 1 wt% of residual 4,4'-BPA imide-anhydride, wherein each amount is based on the total weight of the 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition, wherein the dynamic viscosity of the varnish composition is 30,000 to 120,000 cP, or 30,000 cP to 80,000 cP, or 50,000 to 80,000 cP, or 50,000 to 70,000 cP, as determined at a solids content of 10 wt% in 1- methylpyrrolidin-2-one at 25°C, and wherein a cured product of the varnish composition has a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by differential scanning calorimetry, preferably wherein the 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises greater than or equal to 99 wt%, more preferably greater than or equal to 99.5 wt% of the 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione.

[0006] Also provided is an article manufactured from the varnish composition, preferably wherein the article is a fiber, a layer, a coating, a cast article, a prepreg, a composite, or a laminate.

[0007] Also provided is a cured product of the varnish composition comprising a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; or a thickness of 0.1 to 1,000 micrometers, or 0.1 to 500 micrometers, or 0.1 to 250 micrometers; or a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23 °C, as determined by dielectric spectroscopy; or a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measure at 10 GHz and 23 °C, as determined by dielectric spectroscopy; a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by digital scanning calorimetry (DSC); or a combination thereof.

[0008] Also provided is a method of manufacturing an article from the varnish composition comprising disposing the varnish composition on a substrate; and curing the varnish composition to form the article; preferably wherein the article is a fiber, a layer, a coating, a cast article, a prepreg, a composite, or a laminate.

[0009] The above described and other features are exemplified by the following detailed description.

DETAILED DESCRIPTION

[0010] Described herein is a varnish composition including a polyamic acid and a solvent. The polyamic acid includes structural units derived from reaction of a high purity 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione (also referred to as 4,4'-(4,4'- isopropylidenediphenoxy)bis(phthalic anhydride), 4,4'-bisphenol A dianhydride, or 4,4'-BPADA) with an organic diamine. The purified 4,4'-BPADA, also referred to herein as the 4,4’-isomer, is substantially free from contaminants such as phase transfer agents, various inorganic ionic species including sodium, potassium, calcium, zinc, aluminum, titanium, iron, chromium, molybdenum, nickel, phosphorus, phosphate, nitrate, nitrite, sulfate, and chloride ions, imide-anhydrides, and diacid derivatives resulting from ring opening of an anhydride moiety. The present inventors have discovered the use of a varnish composition obtained from such high purity dianhydride can be used to conveniently provide articles for a variety of applications including laminates, adhesives, coatings, and composites.

[0011] The varnish composition includes a polyamic acid comprising structural units derived from reaction of a 4,4'-BPADA composition with an organic diamine; and a solvent. In the varnish composition, the polyamic acid is derived from a purified 4,4'-BPADA composition that is substantially free of impurities. The 4,4'-BPADA is of formula (1)

[0012] The purified 4,4'-BPADA composition includes the 4,4'-BPADA; 25 parts per million by weight (ppm) or less, or 0.01 to 25 ppm, or 0.01 to 10 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions; 50 ppm or less, or 0.01 to 50 ppm, or 0.01 to 25 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions; 0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt%, or 0.0001 to 0.3 wt% of residual 4,4'- BPA tetraacid (4,4'-BPA-TA); 0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt%, or 0.0001 to 0.3 wt% of residual 4,4'-BPA anhydride diacid (4,4'-BPA-DA); and 0.00001 to 4 wt%, or 0.01 to 4 wt%, or 0.01 to 2 wt%, or 0.05 to 1 wt%, or 0.0001 to 0.1 wt% of residual 4,4'- BPA imide-anhydride (4,4'-BPA-IA). It is to be understood that the purified 4,4'-BPADA is a composition that comprises the 4,4'-BPADA and the recited impurities as described herein. The amounts in weight percent and ppm are based on the total weight of the purified 4,4'-BPADA composition.

[0013] In this regard, the term “purified 4,4'-BPADA” is used for convenience. However, given the presence of one or more impurities in the purified 4,4'-BPADA, for the sake of convenience the term “purified 4,4'-BPADA” is used interchangeably with the term “purified 4,4'- BPADA composition.”

[0014] In an aspect, the purified 4,4'-BPADA includes 0.01 to 25 ppm, or 0.01 to 15 ppm, or 0.01 to 10 ppm total of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions combined, based on the total weight of the purified 4,4'-BPADA.

[0015] In an aspect, the purified 4,4'-BPADA includes 0.01 to 25 ppm, or 0.01 to 15 ppm, or 0.01 to 10 ppm total of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions combined, based on the total weight of the purified 4,4'-BPADA. [0016] In a particular aspect, the purified 4,4'-BPADA includes 0.0002 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt%, or 0.0002 to 0.3 wt% of 4,4'-BPA-TA and 4,4'-BPA-DA combined; 0.01 to 50 ppm, or 0.01 to 25 ppm of sulfate ions; 0.01 to 25 ppm, or 0.01 to 10 ppm of sodium ions; and 0.01 to 25 ppm, or 0.01 to 10 ppm of chloride ions. The amounts in weight percent and ppm are based on the total weight of the purified 4,4'-BPADA.

[0017] In another aspect, the purified 4,4'-BPADA includes 15 ppm or less, or 0.01 to 15 ppm, or 0.01 to 10 ppm of sulfate ions; 10 ppm or less, or 0.01 to 10 ppm, or 0.01 to 5 ppm of sodium ions; 5 ppm or less, or 0.01 to 5 ppm, or 0.01 to 2 ppm of chloride ions; 2 ppm or less, or 0.01 to 2 ppm, or 0.01 to 1 ppm of nitrate ions; and 2 ppm or less, or 0.01 to 2 ppm, or 0.1 to 1 ppm of nitrite ions. The amounts in weight percent and ppm are based on the total weight of the purified 4,4'-BPADA.

[0018] The residual levels of cations (sodium, potassium, zinc, calcium, aluminum, iron, titanium, chromium, molybdenum, nickel, and phosphorus) can be determined by inductively coupled plasma-digestion (ICP-Dig). The residual levels of anions (sulfates, chlorides, phosphates, nitrates, and nitrites) can be determined by extraction-ion chromatography (IC-Extract).

[0019] As used herein, the residual 4,4'-BPA tetraacid (4,4'-BPA-TA) is a compound of formula (2):

[0020] As used herein, the residual 4,4'-BPA anhydride diacid (4,4'-BPA-DA) is a compound of formula (3):

[0021] As used herein, the residual 4,4'-BPA imi de-anhydride (4,4'-BPA-IA) is a compound of formula (4):

wherein R is hydrogen, or a Ci-30 substituted or unsubstituted hydrocarbyl, preferably a Ci_6 alkyl or a C6-20 aryl optionally substituted with 1 to 5 halogens, Ci_₆ alkyl groups, or a combination thereof. Preferably, R is methyl.

[0022] In some aspects, the purified 4,4'-BPADA can further include 0.0001 to 6 wt%, or 0.01 to 6 wt%, or 0.01 to 2 wt%, or 0.01 to 1 wt%, or 0.01 to 0.5 wt%, or 0.01 to 0.1 wt% of a combination of 3,4'-BPADA (0.01 to 6 wt%) of formula (5a), 3,3'-BPADA of formula (5b), 3,4'- BPA-IA of formula (6a) or (6b), or a combination thereof. The amounts in weight percent are based on the total weight of the purified 4,4'-BPADA.

wherein R is the same as defined for formula (4).

[0023] In a particular aspect, the purified 4,4'-BPADA obtained by a high purity hydrolysis ring closure process is >99 wt% of the 4,4'-isomer, preferably >99.5 wt% of the 4,4'-isomer.

[0024] The residual amounts of 4,4'-BPA-TA, 4,4'-BPA-DA, 4,4'-BPA-IA, 3,4'-BPADA, and 3,4'-BPA-IA can be determined by ultra-performance liquid chromatography (UPLC) or carbon- 13 nuclear magnetic resonance (¹³C NMR).

[0025] The varnish composition can have a dynamic viscosity of 20,000 to 120,000 cP, or 20,000 to 80,000 centipoise (cP), as determined at a solids content of 10 wt% in 1-methylpyrrolidin- 2-one (NMP) at 25°C. For example, the varnish composition can have a dynamic viscosity of 20,000 to 120,000 cP, or 30,000 to 120,000 cP, or 20,000 to 80,000 cP, 30,000 to 80,000 cP, or 40,000 to 80,000 cP, or 50,000 to 80,000 cP, or 50,000 to 70,000 cP as determined at a solids content of 10 wt% in NMP at 25°C. It was surprisingly discovered that the varnish composition prepared from the purified 4,4'-BPADA provides a higher dynamic viscosity than expected for such polyamic acid solutions, which are generally less than 20,000 cP when determined at a solids content of 10 wt% in NMP at 25°C. This discovery allows the provision of a high viscosity polyamic acid solution that can be used advantageously for various applications.

[0026] In a particular aspect, the varnish composition includes a polyamic acid prepared from a purified 4,4'-BPADA comprising 0.00002 to 4 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt%, or 0.0002 to 0.3 wt% of 4,4'-BPA-TA and 4,4'-BPA-DA combined; 0.01 to 50 ppm, or 0.01 to 25 ppm of sulfate ions; 0.01 to 25 ppm, or 0.01 to 10 ppm of sodium ions; and 0.01 to 25 ppm, or 0.01 to 10 ppm of chloride ions; wherein the varnish composition has a dynamic viscosity of 30,000 to 120,000 cP, or 30,000 cP to 80,000 cP, or 50,000 to 80,000 cP, or 50,000 to 70,000 cP, as determined at a solids content of 10 wt% in NMP at 25°C. The amounts in weight percent and ppm are based on the total weight of the purified 4,4'-BPADA.

[0027] For example, the varnish composition can include a polyamic acid comprising structural units derived from reaction of 5,5'-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: greater than or equal to 99 wt%, preferably greater than or equal to 99.5 wt% of the 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione; 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions; 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions; 0.0001 to 1 wt%. or 0.0001 to 0.5 wt%, or 0.0001 to 0.3 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 1 wt%, or 0.0001 to 0.5 wt%, or 0.0001 to 0.3 wt% of residual 4,4'-BPA diacid; and 0.00001 to 1 wt%, or 0.00001 to 0.5 wt%, or 0.0001 to 0.1 wt% of residual 4,4'-BPA imide-anhydride, wherein each amount is based on the total weight of the 5,5'-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition, wherein the 5,5'-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition is made by a method comprising: hydrolyzing a 4,4'-BPADA-bisimide to form a corresponding 4,4'-BPADA tetraacid tetrasalt; contacting the 4,4'-BPADA tetraacid tetrasalt with a mineral acid to form a corresponding 4,4'-BPADA tetraacid; contacting the 4,4'-BPADA tetraacid with a halogenated solvent to form a reaction mixture, optionally wherein the halogenated solvent comprises ortho dichlorobenzene, para-dichlorobenzene, meta-dichlorobenzene, trichlorobenzene, or a combination thereof; heating the reaction mixture to a temperature effective to form the corresponding 5,5'-[l- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione from the 4,4'-BPADA tetraacid, optionally in the presence of a mineral acid; and isolating the 5,5'-[l-methylethylidene)bis(4,l- phenyleneoxy)bis- 1,3 -isobenzofurandione from the reaction mixture; optionally wherein the method is carried out in the absence of an organic acid, an organic acid anhydride, or both, and wherein a cured product of the varnish composition has a glass transition temperature of 190 to 260°C, as determined by DSC, and two or more of: a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23°C, as determined by dielectric spectroscopy; or a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measured at 10 GHz and 23°C, as determined by dielectric spectroscopy.

[0028] The purified 4,4'-BPADA can be particularly useful for the preparation of a polyetherimide. Accordingly, provided is a polyetherimide comprising repeating units derived from polymerization of the purified 4,4'-BPADA and an organic diamine. It is to be understood that the term “polymerization of the purified 4,4'-BPADA and an organic diamine” refers to the formation of a polyamic acid and imidization of the polyamic acid as described herein. The 4,4'-BPADA can be prepared according to the methods described herein and can therefore advantageously possess low levels of contaminants.

[0029] The organic diamine used to prepare the polyamic acid of the varnish compound includes one or more diamines that are each independently of formula (7)

H2N-R-NH2 (7) wherein R is a C_6-30 aromatic or heteroaromatic hydrocarbon, a straight or branched chain C_4.20 alkylene, a C3.8 cycloalkylene, or a halogenated derivative thereof. In some aspects, R is a divalent group of one or more of the following formulas

wherein Q¹ is -0-, -S-, -C(O)-, -N=N-, -SO₂-, -SO-, -P(R^a)(=0)- wherein R^a is a Ci-g alkyl or C_6-12 aryl, -C_yH_2y- wherein y is an integer from 1 to 5 or a halogenated derivative thereof (which includes perfluoroalkylene groups), or -(C₆H_I0)_z- wherein z is an integer from 1 to 4. In some aspects. R is meta-phenylene, para-phenylene, or a diarylene sulfone, in particular bis(4,4’-phenylene)sulfone, bis(3,4’-phenylene)sulfone, bis(3,3’-phenylene)sulfone, or a combination thereof. In some aspects, at least 10 mole percent (mol%) or at least 50 mol% of the R groups contain sulfone groups, and in other aspects no R groups contain sulfone groups.

[0030] Exemplary organic diamines include, but are not limited to, 1,4-butane diamine, 1,5- pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine, 1,18-octadecanediamine, 3- methylheptamethylenedi amine, 4,4-dimethylheptamethylenediamine, 4- methylnonamethylenediamine, 5-methylnonamethylenediamine, 2,5- dimethylhexamethylenedi amine, 2,5-dimethylheptamethylenediamine, 2, 2- dimethylpropylenediamine, N-methyl-bis (3-aminopropyl) amine, 3-methoxyhexamethylenediamine, l,2-bis(3-aminopropoxy) ethane, l,3-bis(4-aminophenoxy)benzene, bis(3-aminopropyl) sulfide, 1,4- cyclohexanediamine, bis-(4-aminocyclohexyl) methane, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diamino-toluene, m-xylylenediamine, p-xylylenediamine, 2-methyl-4,6- diethyl-l,3-phenylene-diamine, 5-methyl-4,6-diethyl-l,3-phenylene-diamine, benzidine, 3,3'- dimethylbenzidine, 3,3 '-dimethoxybenzi dine, 1,5-diaminonaphthalene, 9,10-dimethylanthracene, 4,4'-methylenedianiline, 4,4'-oxydianiline, 4,4'-azo-dianiline, bis(4-aminophenyl) methane, bis(2- chloro-4-amino-3,5-diethylphenyl)methane, bis(4-amino-phenyl) propane, 2,4-bis(p-amino-t-butyl) toluene, bis(p-amino-t-butylphenyl) ether, bis(p-methyl-o-aminophenyl) benzene, bis(p-methyl-o- aminopentyl) benzene, l,3-bis(4-aminophenoxy)benzene, l,3-diamino-4-isopropylbenzene, bis(4- aminophenyl) sulfide, 4,4'-diaminodiphenylsulfone, 3,4'-diamino-diphenylsulfone, 3,3'- diaminodiphenylsulfone, bis(4-aminophenyl) ether, 2,6-diamino, 3,3'-diamino-benzophenone, 4,4'- diaminobenzophenone, a regioisomer thereof, a C alkylated or poly(Ci_₄)alkylated derivative thereof, a halogenated derivative thereof, or a combination thereof. In an aspect, the organic diamine is meta-phenylene diamine, para-phenylene diamine, ortho-phenylene diamine, 4,4'-diamino- diphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4, 4'-oxy dianiline, 1,3- bis(4-aminophenoxy)benzene, or a combination thereof. In another aspect, the organic diamine is m- phenylene-diamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3 '-diamino-diphenyl sulfone, or a combination thereof.

[0031] The purified 4,4'-BPADA can be prepared by a hydrolysis ring closure route that includes the steps of hydrolysis of a 2-hydrocarbyl-5-[4-[2-[4-(2-hydrocarbyl-l,3-dioxoisoindol-5- yl)oxyphenyl]-propan-2-yl]phenoxy]isoindole-l,3-dione (also known as 2,2-bis[4-(V- hydrocarbylphthalimido-4-oxy)phenyl]propane or 4,4'-BPA-bisimide) to the corresponding tetraacid salt followed by acidification and dehydration to form BPADA (as described, for example, in U.S. Patent Nos. 3,879,428; 3,957,862; 3,905,942; and 4,054,600, and U.S. Patent Pub. Nos. 2007/0117990; and 2019/00092726), followed by various downstream processes. The 4,4'-BPADA- bisimide is of formula (8)

wherein R is hydrogen, or a Ci-₃₀ substituted or unsubstituted hydrocarbyl, preferably a C_M alkyl or a C_6-20 aryl optionally substituted with 1 to 5 halogens, C_M alkyl groups, or a combination thereof. Preferably, R is methyl.

[0032] For example, purified 4,4'-BPADA can be prepared by a method including hydrolyzing a 4,4'-BPADA-bisimide to form the corresponding 4,4'-BPADA-TA tetrasalt, quenching the 4,4'-BPADA-TA tetrasalt with a mineral acid to form the 4,4'-BPADA-TA, contacting the 4,4'- BPADA-TA with a halogenated solvent to form a reaction mixture; heating the reaction mixture to a temperature effective to form the corresponding 4,4'-BPADA from the 4,4'-BPADA-TA, optionally in the presence of an aliphatic carboxylic acid, a corresponding aliphatic anhydride, or a mineral acid; and isolating the purified 4,4'-BPADA from the reaction mixture. The method of making the purified 4,4'-BPADA composition is preferably conducted in the absence of an organic acid, an organic acid anhydride, or both.

[0033] An exemplary 4,4'-BPADA-TA tetrasalt is the tetrasodium salt of formula (9):

[0034] The hydrolyzing of the 4,4'-BPADA-bisimide can be performed in the presence of 4 to 100, 4 to 50, 4 to 25, 4 to 10, 4 to 6, or 4 to 5 equivalents of a base, based on the 4,4'-BPADA- bisimide, for example an alkali metal hydroxide (such as sodium hydroxide or potassium hydroxide). The hydrolyzing can be performed under aqueous conditions for an effective amount of time, for example 1 to 10 hours, or 2 to 8 hours, at atmospheric pressure or elevated pressure. Organic co solvents can optionally be added. Exemplary organic solvents include optionally substituted Ci-₆ aliphatic alcohol such as methanol, ethanol, isopropanol, ethylene glycol, higher poly(alkylene glycol)s, or 1 -butanol. Organic co-solvents can optionally be added. The hydrolyzing can be conducted at a temperature of 65 to 200°C, or 75 to 130°C, and optionally at elevated pressure.

[0035] The mineral acid can be HC1, H₂SO₄, H₃PO₄, HNO₃, or the like. The acid can be present in an amount of 2 to 10 molar equivalents, 3 to 8 molar equivalents, or 4 to 8 molar equivalents based on the 4,4'-BPADA-bisimide.

[0036] The halogenated solvent can be an aromatic halogenated solvent, for example, ortho dichlorobenzene, para-dichlorobenzene, meta-dichlorobenzene, trichlorobenzene, or a combination thereof.

[0037] In some aspects, the 4,4'-BPADA can be further purified. The method for purification can include contacting the dianhydride with a halogenated solvent to form a solution. The method can further include one or more of filtering the solution to remove ionic species; washing the solution with aqueous media to remove ionic species; crystallizing the dianhydride from the solution to remove ionic species; and contacting the solution with an adsorbent to remove ionic species. The filtering can include passing the solution through a filter having a pore size of less than or equal to 2 micrometers (pm), or less than 1 pm, or 0.2 to 0.45 pm. The crystallizing can include adding an antisolvent to the solution and cooling the solution to a temperature effective to provide a slurry, such as to temperature of 20 to 100°C, or 50 to 100°C, or 65 to 85°C. The antisolvent can be a non-polar solvent, such as heptane, hexane, pentane, benzene, ligroin, or a combination thereof. The adsorbent can be, for example, diatomaceous earth, silica, alumina, ion-exchange resin, or a combination thereof, and the solution comprising the adsorbent can be filtered through a filter having a pore size of 60 pm or less, or 40 to 60 pm.

[0038] The solvent of the varnish composition can be, for example, N,N- dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N- dimethylmethoxyacetamide, N-methyl-2-pyrrolid-one, N-cyclohexylpyrrolidinone, N- methylcaprolactam, l,3-dimethyl-2-imidazolidone, 1 ,2-dimethoxy-ethane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, g-butyrolactone, g-caprolactone, dimethyl-sulfoxide, benzophenone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diglyme, triglyme, tetra-glyme, N,N- dimethylethyleneurea, N,N-dimethylpropyleneurea, tetramethylurea, propylene glycol phenyl ether, anisole, veratrole, o-dichlorobenzene, chlorobenzene, trichloroethane, methylene chloride, chloroform, pyridine, picoline, ethyl lactate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate, ethyl carbitol acetate, propylene carbonate, sulfolane, an ionic liquid, or a combination thereof.

[0039] Preferably, the solvent is anhydrous and does not include water. For example, the solvent can include less than 100 ppm, or less than 50 ppm, or less than 10 ppm of water.

[0040] The amount of solvent in the varnish composition, which is generally the same amount of solvent used to prepare the polyamic acid, is not particularly limited. The solids content can be from 1 to 35 wt%, based on the total weight of the varnish composition. For example, the solids content can be from 1 to 30 wt%, 10 to 30 wt%, 20 to 30 wt%, 10 to 25 wt%, 10 to 20 wt%, or 5 to 15 wt%, based on the total weight of the varnish composition.

[0041] The polyamic acid of the varnish composition can be prepared by combining the purified 4,4'-BPADA, the organic diamine and optionally other diamine components, and the solvent by stirring until a viscous solution is formed. For example, a method of manufacturing the varnish composition can include combining the components of the varnish composition, and heating the components with agitation or stirring at a temperature and for a period of time effective to dissolve the components in the solvent, or at a temperature lower than the boiling point of the solvent. The temperature is not particularly limited, and can be selected to avoid instability of the polyamic acid. Preferably, the temperature is 50°C or less, or 30°C or less, or 25°C or less.

[0042] To prepare the varnish composition, the organic diamine component can be included in an amount of from 0.5 to 2.0 moles, or from 0.8 to 1.5, or from 0.9 to 1.1 moles, or 0.999 to 1.001 moles per mole of dianhydride component. The poly condensation to form the polyamic acid of the varnish composition is exothermic and the reaction mixture can be cooled to below room temperature as appropriate.

[0043] In an aspect, the varnish composition can be prepared from a combination of 40 wt% or greater of the combined dianhydride and organic diamine, based on the total weight of the dianhydride, organic diamine, and solvent.

[0044] In some aspects, an end-capping agent is present during the reaction to control the molecular weight of the polyamic acids and thus the polyetherimides formed from the polyamic acids. Exemplary end capping agents include, but are not limited to phthalic anhydride, substituted mono anhydrides, aniline, Ci-Cig linear, branched or cyclic aliphatic monoamines, and monofunctional aromatic amines. In some aspects, the end capping agent is phthalic anhydride and the varnish composition includes 0.01 to 4 mol%, or 0.01 to 2 mol%, or 0.05 to 1 mol% of residual phthalic anhydride, based on the total weight of the purified 4,4'-BPADA. For example, the purified 4,4'-BPADA composition may include greater than or equal to 99.5 wt% of the 4,4'-BPADA and the end capping agent may be phthalic anhydride, wherein the varnish composition may include 0.01 to 0.5 mol%, or 0.01 to 0.5 mol%, or 0.05 to 0.5 mol% of residual phthalic anhydride, based on the total weight of the purified 4,4'-BPADA composition.

[0045] Curing the varnish composition forms a polyetherimide. When prepared according to the method described herein and using the purified 4,4'-BPADA, the cured varnish composition can advantageously have low levels of residual impurities. For example, the cured product includes less than 25 ppm, for example 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium, molybdenum, nickel, and phosphorus ions, and less than 50 ppm, for example 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions.

[0046] The polyetherimides can have a melt index of 0.1 to 10 grams per minute (g/min), as measured by ASTM D1238 at 340 to 370°C, using a 6.7-kilogram (kg) weight. In some aspects, the polyetherimide has a weight average molecular weight (M_w) of 1,000 to 500,000 grams/mole (g/mol), as measured by gel permeation chromatography (GPC), using polystyrene standards. In some aspects, the polyetherimide has an Mw of 10,000 to 250,000 g/mol, or 25,000 to 200,000 g/mol, or 50,000 to 200,000 g/mol. Such polyetherimides can have an intrinsic viscosity greater than 0.2 deciliters per gram (dL/g), or, more specifically, 0.35 to 0.7 dL/g as measured in m-cresol at 25°C.

[0047] The varnish composition can be used in the manufacture of articles useful for a wide variety of applications. An article can be manufactured from the varnish composition by, for example, forming the article from the varnish composition, for example by casting, molding, extruding, or the like, and removing the solvent from the formed article. Exemplary articles can be in the form of a fiber, a layer, a conformal coating, a cast article, a prepreg, or a cured composite. In some aspects, the article can be a layer, and can be formed by casting the varnish composition onto a substrate to form a cast layer. The solvent can be removed by any number of means, including by heating the cast layer, heating the cast layer under heat and pressure, for example by laminating the cast layer to another substrate. In some aspects, articles prepared by the above-described methods can include adhesives, packaging material, capacitor films, or circuit board layers. In some aspects, articles prepared from the varnish composition can be a polyetherimide dielectric layer, or a coating disposed on a substrate, for example a wire or cable coating. In a preferred aspect, the article can be a polyetherimide dielectric layer in a circuit material, for example in a printed circuit board, used, for example, in lighting or communications applications. Other exemplary articles prepared from the varnish composition can be painted layers to inhibit corrosion, coatings to provide thermal resistance, coatings for smoothing a surface, or the like.

[0048] In some aspects, the article can further comprise a fibrous preform, for example, a fibrous preform comprising any one or more of the above-described fabrics. When the article comprises a fibrous preform, the method of manufacturing the article can include forming the article from the varnish composition by coating or impregnating the preform with the varnish. The impregnated fibrous preform can optionally be shaped before or after removing the solvent.

[0049] In some aspects, articles prepared from a varnish composition that further comprises a thermosetting polymer composition. When the varnish composition comprises a thermosetting polymer composition, the method of manufacturing the articles from the varnish composition can further comprise partially curing the thermosetting polymer composition to form a prepreg, or fully curing the thermosetting polymer composition to form a composite article. The curing can be before or after removing the solvent from the varnish composition. In addition, the article can be further shaped before removal of the solvent or after removal of the solvent, before curing, after partial curing, or after full curing, for example by thermoforming. In an aspect, the article is formed, and the solvent is removed; the article is partially cured (B-staged); optionally shaped; and then further cured.

[0050] Exemplary thermosetting polymers include epoxy resin, polyester resin, polyimide resin, bis-maleimide resin, cyanate ester resin, vinyl resin, benzoxazine resin, benzocyclobutene resin, phenol resin, urea resin, melamine-formaldehyde resin, urea-formaldehyde latex, xylene resin, diallylphthalate resin, aniline resin, furan resin, polyurethane, mineral filled silicone, or a combination thereof. When the polyetherimide dielectric layer further comprises a thermoset polymer, the thermoset polymer can be uncured or partially cured before laminating, and fully cured during or after the laminating. Alternatively, the thermosetting polymer can be fully cured prior to lamination. In some aspects, the thermosetting polymer can be partially cured during and/or after solvent removal, or the thermosetting polymer can be fully cured during or after solvent removal. Following removal of the solvent and fully curing the thermosetting polymer, the resulting polyetherimide layer can have at least one of improved flame retardance, improved toughness, and improved peel strength from copper, compared to the thermosetting polymer alone.

[0051] Exemplary articles prepared from the varnish composition for various applications can include copper clad laminates (CCL), for example, metal core copper clad laminates (MCCCL), composite articles, and coated articles, for example multilayer articles. Methods of manufacturing such articles represent another aspect of the disclosure.

[0052] In an exemplary aspect, a polyetherimide dielectric layer prepared from the above- described varnish composition can be useful in a circuit assembly, for example, in a metal-clad laminate such as a copper clad laminate. For example, a laminate can comprise a polyetherimide dielectric layer, a conductive metal circuit layer disposed on the polyetherimide dielectric layer, and optionally, a heat dissipating metal matrix layer disposed on the dielectric layer on a side opposite the conductive metal layer. In some aspects, the polyetherimide dielectric layer can optionally comprise a fibrous preform (e.g., a fabric layer) and/or a thermosetting polymer composition. For example, the polyetherimide dielectric layer can further comprise a glass fabric layer or a cured thermoset polymer.

[0053] The conductive metal layer can be in the form of a circuit, and can be copper, zinc, tin, brass, chromium, molybdenum, nickel, cobalt, aluminum, stainless steel, iron, gold, silver, platinum, titanium, or an alloy containing one or more of these metals. Other metals include, but are not limited to, a copper molybdenum alloy, a nickel-cobalt iron alloy such as KOVAR, available from Carpenter Technology Corporation, a nickel-iron alloy such as INVAR, available from National Electronic Alloys, Inc., a bimetal, a trimetal, a trimetal derived from two-layers of copper and one layer of INVAR, and a trimetal derived from two layers of copper and one layer of molybdenum. In some aspects, exemplary metal layers comprise copper or a copper alloy. Alternatively, wrought copper foils can be used. In a preferred aspect, the conductive metal layer comprises copper and the laminate is a copper clad laminate.

[0054] Conductive metal layers can have a thickness of 2 to 200 micrometers (pm), specifically 5 to 50 pm, and more specifically 5 to 40 pm.

[0055] A heat dissipating metal matrix layer can be a thermally conductive metal such as aluminum, boron nitride, aluminum nitride, copper, iron, steel, or the like. A thermally conductive, electrically conductive metal can be used provided that the metal is electrically isolated from the metal circuit layer. Preferred supporting metal matrix layers can have a thickness of 0.1 to 20 millimeters (mm), specifically 0.5 to 10 mm, and more specifically 0.8 to 2 mm. In a preferred aspect, the metal matrix layer comprises aluminum.

[0056] The conductive metal layer and the supporting metal matrix layers can be pretreated to have high surface roughness for enhanced adhesion to the dielectric layer. Treatment methods include washing, flame treatment, plasma discharge, corona discharge, or the like, for example to enhance adhesion of the metal layer. In some aspects, the dielectric layer can adhere firmly to the conductive metal layer or the heat dissipation layer without using an adhesive. In other aspects, an adhesive can be used to improve adhesion of the dielectric layer to the conductive metal layer or the heat dissipation layer. Exemplary adhesives used to bond the composite sheet to a metal (if an adhesive is used) are polyimide adhesives, acrylic adhesives, or epoxies.

[0057] The copper clad laminates can be made by thermal lamination of one or more dielectric layers, one or more conductive metal layers, and a supporting metal matrix layer, under pressure without using thermosetting adhesives. The dielectric layer can be prepared from the varnish composition, and this layer can be prepared prior to the thermal lamination step, for example, by a solvent casting process to form the dielectric layer. In some aspects, the dielectric layer, the conductive metal layer, and the thermal dissipation layer are thermally laminated together by an adhesive-free process under pressure to form a laminate. In another aspect, a dielectric layer is placed between the conductive metal layer and a layer of woven fabric, and thermally laminated under pressure in a single step. The conductive metal layer can optionally be in the form of a circuit before laminating. Alternatively, the conductive metal layer can optionally be etched to form the electrical circuit following lamination. The laminating can be by hot press or roll calendaring methods, for example, a roll-to-roll method.

[0058] Alternatively, laminates for a circuit assembly can be made by a solution casting method in which the varnish composition is cast directly onto the conductive metal layer, followed by lamination to the heat dissipating metal matrix layer. In another aspects, the varnish composition can be cast directly onto the heat dissipating metal matrix layer, followed by lamination to the electrically conductive metal layer.

[0059] Multilayer laminates comprising additional layers can also be made by thermal lamination in one step or in two or more consecutive steps by such processes as hot press or roll calendaring methods. In some aspects, seven layers or fewer can be present in the laminate and in other aspects, sixteen layers or fewer. For example, a laminate can be formed in one step or in two or more consecutive steps with sequential layers of fabric-dielectric layer-conductive metal layer- dielectric layer-fabric-dielectric layer-metal foil, or a sub-combination thereof with fewer layers, such that the laminate comprises a dielectric layer comprising a film derived from the varnish composition between any conductive metal layer and any fabric layer. In another aspect, a first laminate can be formed in one step or in two or more consecutive steps with a layer of fabric between two dielectric layers, such as a layer of a woven glass fabric disposed between two dielectric layers.

A second laminate can then be prepared by laminating a conductive metal layer to a dielectric layer of the first laminate.

[0060] In a specific aspect, the laminates can be prepared by a method comprising the steps of laminating the polyetherimide dielectric layer to the conductive metal circuit layer under heat, pressure, or a combination thereof, and optionally, subsequently, or simultaneously laminating the polyetherimide dielectric layer to the heat dissipating supporting metal matrix layer. The supporting metal matrix layer is disposed on the polyetherimide layer in a side opposite the conductive metal layer. The polyetherimide layer can be prepared by casting the varnish composition onto a substrate, and removing solvent from the cast layer. Alternatively, the varnish composition can be directly cast onto a conductive metal circuit layer, and the solvent can be removed to provide the polyetherimide dielectric layer.

[0061] In some aspects, the polyetherimide layer can further comprise a woven or nonwoven glass fabric. When the polyetherimide layer further comprises a glass fabric, the polyetherimide layer can be prepared by impregnating the glass fabric with a varnish composition, and removing the solvent from the impregnated glass fabric.

[0062] The conductive metal layer in a copper clad laminate can further be patterned to provide a printed circuit board. Furthermore, the copper clad laminates can be shaped to provide a circuit board having the shape of a sheet, a tube, or a rod. The copper clad laminates can have a thermal conductivity of greater than or equal to 0.3 W/m-K.

[0063] Printed circuit boards prepared from the varnish composition can have an overall thickness of 0.1 to 20 millimeters (mm), and specifically 0.5 to 10 mm, wherein overall thickness refers to an assembly comprising a layer each of the polyetherimide dielectric layer, the electrically conductive metal layer, and the supporting metal matrix layer. Circuit assemblies can have an overall thickness of 0.5 to 2 mm, and specifically 0.5 to 1.5. There is no particular limitation on the thickness of the polyetherimide dielectric layer as long as a desired overall thickness of the laminate is achieved. For example, the thickness of the polyetherimide dielectric layer can be 5 to 1500 pm, or 5 to 750 pm, or 10 to 150 pm, or 10 to 100 pm. In an aspect, the printed circuit board can be a metal core printed circuit board (MCPCB) for use in a light emitting diode (LED) application.

[0064] Articles comprising the circuit assemblies are another aspect of the disclosure.

Articles include those comprising printed circuits as used in medical or aerospace industries. Still other articles include antennae and like articles. Exemplary articles include, but are not limited to, those comprising printed circuit boards, which are used, for example, in lighting, solar energy, displays, cameras, audio and video equipment, personal computers, mobile telephones, electronic notepads, and like devices, or office automation equipment. For example, electrical parts can be mounted on printed circuit boards comprising a laminate.

[0065] In some aspects, a method of manufacturing a composite article can comprise impregnating a porous base material with a varnish composition, optionally comprising a thermosetting polymer composition, and subsequently removing the solvent from the impregnated porous base material, and optionally followed by curing. As used herein, a “porous base material” can be any base material having any size pores or openings that are interconnected or not interconnected. Thus, a porous base material may be a fibrous preform or substrate as described above or other porous material comprising a ceramic, a polymer, a glass, carbon, or a combination thereof. For example, the porous base material can be woven or non-woven glass fabric, a fiberglass fabric, or carbon fiber. The thermosetting polymer composition can be partially cured to form a prepreg, or can be fully cured to form a reinforced composite article. Removing the solvent from the impregnated porous base material can be achieved by heating, compressing, or heating and compressing the material. The impregnated porous base material can optionally be shaped before or after the partial curing step, and before or after the solvent removal step. The impregnated porous base material can also be shaped after curing, by thermoforming, for example.

[0066] The composite article prepared by the above-described method can be in the form of a fiber, a layer, a cast article, a prepreg, a wire coating, a molded article, a compression article, or a reinforced composite article. [0067] In another aspect, the varnish composition can be used as a coating, for example in the preparation of a multilayer article. A method of manufacturing the coating can comprise the steps of combining the varnish composition and a fluoropolymer (e.g., polytetrafluoroethylene-ethylene copolymers, tetrafluoroethylene-perfluoroalkylvinylether copolymers, tetrafluoroethylene- hexafluoropropylene copolymers, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymers, polyvinylidene fluoride, or a combination thereof), a thermosetting polymer composition (e.g., epoxy resin, polyester resin, polyimide resin, bis-maleimide resin, cyanate ester resin, vinyl resin, benzoxazine resin, benzocyclobutene resin, phenol resin, urea resin, melamine- formaldehyde resin, urea-formaldehyde latex, xylene resin, diallylphthalate resin, aniline resin, furan resin, polyurethane, mineral filled silicone, or a combination thereof), or a combination thereof, and forming a coating on a substrate. In another aspect, a multilayer article can be manufactured by forming a layer comprising the varnish composition, removing the solvent from the layer and optionally curing to provide a primer layer, forming a second layer comprising a ceramic (e.g.,

A1₂0₃, TI0₂, Zr0₂, Cr₂0₃, Si0₂, MgO, BeO, Y₂0₃, A1₂0₃-SI0₂, MgO-Zr0₂, SiC, WC, B₄C, TiC, Si₃N₄, TiN, BN, AIN, TiB, ZrB₂, or a combination thereof), a thermosetting polymer composition, a fluoropolymer, or a combination thereof on the primer layer to provide the multilayer article, and optionally thermally treating the multilayer article to cure the thermosetting polymer composition and/or the varnish composition. Removing the solvent from the primer layer can be by heating the layer, compressing the layer, or heating and compressing the layer. In some aspects, the second layer can further comprise the varnish composition. When the second layer comprises the varnish composition, the method of manufacturing the multilayer article can further comprise the step of removing the solvent from the second layer and optionally curing the varnish composition.

[0068] It is to be understood that the above-described articles and polyetherimide dielectric layers are derived from the varnish composition. For example, the varnish composition can be disposed on a substrate and cured to form the polyetherimide dielectric layer. The polyamic acid of the varnish composition can be cured, or imidized, under conditions effective to provide a corresponding polyetherimide. The curing can be performed in the presence of a solvent, and the solvent subsequently removed after curing. Alternatively, at least a portion of the solvent can be removed prior to curing. Conditions effective to cure the varnish composition can include a temperature of 150 to 380°C, and optionally a solids content of 1 to 50 wt%, or 20 to 40 wt%, or 25 to 35 wt%. Curing can be conducted for 1 to 24 hours, or 2 to 24 hours, or 3 to 16 hours. The curing can be conducted at reduced, atmospheric, or elevated pressure.

[0069] In an aspect, the cured product of the varnish composition can have a peel strength of greater than 1.3 Newtons per millimeter (N/mm), or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8.

[0070] In an aspect, the cured product of the varnish composition can have a thickness of 0.1 to 1,000 mih, or 0.1 to 500 mih, or 0.1 to 250 mih.

[0071] In an aspect, the cured product of the varnish composition can have a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 gigahertz (GHz) and 23°C, as determined by dielectric spectroscopy.

[0072] In an aspect, the cured product of the varnish composition can have a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measure at 10 GHz and 23 °C, as determined by dielectric spectroscopy.

[0073] In an aspect, the cured product of the varnish composition can have a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by DSC.

[0074] In another aspect, the cured product of the varnish composition can have two or more of a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23°C, as determined by dielectric spectroscopy; a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measure at 10 GHz and 23 °C, as determined by dielectric spectroscopy; or a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by DSC; wherein the cured product of the varnish composition can have a thickness of 0.1 to 1,000 pm, or 0.1 to 500 pm, or 0.1 to 250 pm.

[0075] In another aspect, the cured product of the varnish composition can have three or more of a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23 °C, as determined by dielectric spectroscopy; a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measure at 10 GHz and 23 °C, as determined by dielectric spectroscopy; or a glass transition temperature of 190 to 400°C, or 190 to 300°C, or 190 to 260°C, as determined by DSC; wherein the cured product of the varnish composition can have a thickness of 0.1 to 1,000 pm, or 0.1 to 500 pm, or 0.1 to 250 pm.

[0076] In another aspect, the cured product of the varnish composition has a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23 °C, as determined by dielectric spectroscopy; a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measure at 10 GHz and 23 °C, as determined by dielectric spectroscopy; and a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by DSC; wherein the cured product of the varnish composition can have a thickness of 0.1 to 1,000 pm, or 0.1 to 500 pm, or 0.1 to 250 pm.

[0077] This disclosure is further illustrated by the following examples, which are non- limiting.

EXAMPLES

[0078] The materials used in the following Examples are described in Table 1.

Table 1

[0079] The dynamic viscosities of Example 1 and Comparative Example 1 were obtained using a Brookefield DV3T rheometer operating a CPA-41-Z cone and plate sample cell. Dynamic Viscosities were measured at 25°C in centipoise (cP).

[0080] Unless otherwise noted, impurities are evaluated by ultra-performance liquid chromatography (UPLC) or carbon-13 nuclear magnetic resonance (¹³C NMR). UPLC analyses are performed on a Waters ACQUITY UPLC BEH Cl 8 1.7 micrometer 2.1x50 mm column at 35°C. PDA detection was performed at 254 nm with a flow rate of 0.313 mL/min. A gradient method was used with a dual solvent system of acetonitrile and acidic water (4 L DI H₂0 + 3 mL 85% H₃PO₄).

¹³C NMR analyses are performed by dissolving the sample in a solution of CDCI₃ and adding several drops of hexafluroroisopropanol (HFIP) for solubility.

[0081] All residual levels of metals (sodium, potassium, zinc, calcium, aluminum, iron, titanium, chromium, molybdenum, nickel, and phosphorus) are determined by an inductively coupled plasma-digestion (ICP-Dig) method which uses an ICP spectrometer equipped with: an axial and/or radial viewing, a Gem Cone and/or Ultrasonic nebulizer, and a microwave digestion system equipped with appropriate sample digestion vessels set. Samples are prepared using concentrated nitric acid, hydrochloric acid, sulfuric acid, and/or hydrofluoric acid - Supra pure grades.

[0082] Residual levels of anions (sulfates, chlorides, phosphates, nitrates, nitrites) are measured by extraction-ion chromatography (IC-Extract). Sample are prepared by dissolving in methylene chloride optionally with HFIP added to help with solubility. The solutions are then extracted with deionized water, and then the aqueous extracts were analyzed using a calibrated Dionex ICS 2000 instrument. Some samples are analyzed total ion chromatography combustion (IC- Total).

[0083] DSC measurements of the film samples (~5 mg) were performed with a TA Q1000 DSC instrument. The film samples were scanned from 40-350°C under nitrogen atmosphere. The glass transition temperature (T_g) was determined from the second heating scan. Heating rate of 20°C/min was used in these experiments.

[0084] Water absorption of polyetherimide films was determined by % difference in wet weight of film to conditioned weight of film, over conditioned weight of film. In order to obtain the wet weight, films were immersed in deionized water for 24 hours, patted dry to remove surface moisture, and quickly placed in an airtight container before the weight was measured. To obtain the conditioned weight, the polyetherimide films were dried at 100°C under vacuum for 24 hours and quickly moved into an airtight container before the weight was measured.

[0085] Dielectric constant (D_k) and dissipation factor (D_f) were measured using a split post dipole resonator, at a frequency of 10 gigahertz (GHz). Films were equilibrated at 23-25°C, 48-52 % relative humidity (RH) environment for 24 hours before measurement in the same environment.

[0086] Peel strength values were determined according to IPC 2.4.8, “Peel Strength of Metallic Clad Laminates,” Revision C, December 1994, except that the specimen size was 12 centimeters (cm) x 12 cm with a thickness of 1 millimeter (mm). At least four resist strips having a width of 5 mm were cut from the same copper clad laminate. The test strip was peeled back 5 cm at the tab end. The clamp was attached to the peeled back end of the test strip. The specimen was fastened with the hold down fixture so that an unencumbered vertical pull could be exerted. The end of the test strip was in a vertical position ready for testing. The tester was started, and force was applied in the vertical direction at the rate of 50.8 mm per minute (mm/min), until an 8 cm peel was completed. The minimum load was observed and recorded. The actual width of the test strip was measured and recorded. If the full width of the test strip did not peel, the results were discarded, and another strip was evaluated. The peel strength, expressed in units of Newtons per mm (N/mm) was calculated according to the formula: N = LM/WS, where LM is the minimum load (N) and WS is the width of peel strip (mm).

Preparation of Purified 4,4'-BPADA

[0087] 4,4'-BPADA was prepared by a high purity hydrolysis ring closure process as follows. 4,4'-BPADA-bisimide was hydrolyzed with aqueous NaOH at 135°C and 45 psig to form a corresponding 4,4'-BPADA-TA tetrasodium salt. The 4,4'-BPADA-TA tetrasodium salt tetrasodium salt was contacted with sulfuric acid and then washed with water to form a corresponding 4,4'- BPADA-TA. The 4,4’-BPADA-TA was then contacted with ortho-dichlorobenzene to form a reaction mixture, which was subsequently heated to form 4,4'-BPADA. The purified 4,4'-BPADA was then isolated from the reaction mixture and used for Example 1.

Example 1 [0088] A reaction vessel fitted with a stirrer, a heating unit, and a nitrogen inlet was charged with 1.24 g of ODA and 40 g of NMP. To this solution was added 3.222 g of the purified 4,4'-BPA- DA obtained as above and the resulting mixture was stirred over several hours at 23 °C to afford a viscous polyamic acid solution at 10 wt% solids.

Comparative Examples 1 and 2

[0089] Comparative examples 1 and 2 were prepared in an analogous manner as the method described in Example 1, using the same ratio of amine to anhydride, except that 4,4'-BPA-DA was prepared as described in U.S. Patent Nos. 4,329,291; 4,329,292; 4,329,496; and 4,340,545. The resulting material was further purified by recrystallization from ortho-dichlorobenzene (Comparative Example 1) or was used directly (Comparative Example 2).

[0090] Table 2 shows the dynamic viscosities of the polyamic acid solutions (10 wt% solids, NMP, 25°C) of Example 1 and Comparative Examples 1-2.

Table 2

[0091] As shown in Table 2, the polyamic acid solution prepared from the purified 4,4'- BPADA obtained by a high purity hydrolysis ring closure process (Example 1) achieves a dynamic viscosity of 60,000 cP. By comparison, the polyamic acid solutions prepared from the 4,4'-BPADA that was not obtained by the high purity hydrolysis ring closure process only achieved dynamic viscosities of 16,000 cP (Comparative Example 1) and 50 cP (Comparative Example 2).

[0092] Table 3 shows the amounts (wt%) of impurities present in the respective 4,4'-BPADA used to prepare the polyamic acids of Example 1 and Comparative Examples 1-2.

Table 3

[0093] In Table 3, the tetraacid is 4,4'-BPA-TA, the diacid is 4,4'-BPA-DA, the total acid is the sum of 4,4'-BPA-TA and 4,4'-BPA-DA, the imide-anhydride is 4,4'-BPA-IA (as shown in formula (4) where R is methyl), and the 4,4'-isomer refers to the amount of 4,4'-isomer of BPADA (rather than the corresponding 3,3'- or 3,4'-isomers of BPADA).

[0094] As shown in Table 3, the purified 4,4'-BPADA obtained by a high purity hydrolysis ring closure process (Example 1) is >99.5 wt% of the 4,4'-isomer and has less than 0.3 wt% each of tetraacid and diacid, less than 0.3 wt% of total acid, and less than 0.03 wt% of imide-anhydride impurities, based on the total weight of the 4,4'-BPADA. The comparative 4,4'-BPADA of Comparative Examples 1 and 2 did not have the same level of purity as the 4,4'-BPADA used in Example 1.

Example 2

[0095] The polyamic acid solution of Example 1 was solvent cast onto a clean glass substrate and heated at 100°C under a vacuum to remove the solvent to afford a film. The resulting film was removed from the substrate, transferred to a tenter frame, and heated at 150°C for 1 hour and then at 285°C for 2 hours.

Comparative Example 3

[0096] A reaction vessel fitted with a stirrer, a heating unit, and a nitrogen inlet was charged with 6.4985 g of ODA and 100 g of NMP. To this solution was added 10.1711 g of 4,4'-ODPA and the resulting mixture was stirred over several hours at 23 °C to afford a viscous polyamic acid solution at 15 wt% solids. The polyamic acid solution was solvent cast onto a clean glass substrate and imidization was performed by the same method as in Example 2.

Comparative Example 4

[0097] The same procedure as in Comparative Example 3 was used, except PMDA was used instead of 4,4'-ODPA.

[0098] Table 4 shows the properties of Example 2 and Comparative Examples 3-4.

Table 4

[0099] As shown in Table 4, the film of Example 2 had lower glass transition temperature, water absorption, dielectric constant, and dissipation factor compared with the films of Comparative Examples 3 and 4. The film of Example 2 had greater peel strength compared with the films of Comparative Examples 3 and 4.

[0100] This disclosure further encompasses the following Aspects.

[0101] Aspect 1. A varnish composition comprising a polyamic acid comprising structural units derived from reaction of 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5,5’ -[1- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’- [l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 25 ppm or less, or 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions; 50 ppm or less, or 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions; 0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of residual 4,4'-BPA diacid; and 0.00001 to 4 wt%, or 0.01 to 4 wt%, or 0.01 to 2 wt%, or 0.05 to 1 wt% of residual 4,4'-BPA imi de anhydride, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l- phenyleneoxy)bis-l,3-isobenzofurandione, wherein a dynamic viscosity of the varnish composition is 20,000 to 120,000 cP, or 20,000 to 80,000 cP, or 40,000 to 80,000 cP, as determined at a solids content of 10 wt% in l-methylpyrrolidin-2-one at 25 °C, and wherein a cured product of the varnish composition has a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by differential scanning calorimetry, preferably wherein the 5,5’ -[1- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises greater than or equal to 99 wt%, more preferably greater than or equal to 99.5 wt% of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione.

[0102] Aspect 2. The varnish composition of aspect 1, wherein the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’- [l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 0.0002 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of the residual 4,4'-BPA tetraacid and the residual 4,4'- BPA diacid combined; 0.01 to 50 ppm, or 0.01 to 25 ppm of sulfate ions; 0.01 to 25 ppm, or 0.01 to 10 ppm of sodium ions; and 0.01 to 25 ppm, or 0.01 to 10 ppm of chloride ions, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition.

[0103] Aspect 3. The varnish composition of any one or more of the preceding aspects, wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 15 ppm or less, or 0.01 to 15 ppm, or 0.01 to 10 ppm of sulfate ions; 10 ppm or less, or 0.01 to 10 ppm, or 0.01 to 5 ppm of sodium ions; 5 ppm or less, or 0.01 to 5 ppm, or 0.01 to 2 ppm of chloride ions; 2 ppm or less, or 0.01 to 2 ppm, or 0.01 to 1 ppm of nitrate ions; and 2 ppm or less, or 0.01 to 2 ppm, or 0.01 to 1 ppm of nitrite ions, wherein each amount is based on the total weight of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition.

[0104] Aspect 4. The varnish composition of any one of the preceding aspects, wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 0.0002 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of the combination of 4,4'-BPA tetraacid and 4,4'-BPA diacid combined; 0.01 to 50 ppm, or 0.01 to 25 ppm of sulfate ions; 0.01 to 25 ppm, or 0.01 to 10 ppm of sodium ions; and 0.01 to 25 ppm, or 0.01 to 10 ppm of chloride ions, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition; and the dynamic viscosity of the varnish composition is 30,000 to 120,000 cP, or 30,000 cP to 80,000 cP, or 50,000 to 80,000 cP, or 50,000 to 70,000 cP, as determined at a solids content of 10 wt% in l-methylpyrrolidin-2-one at 25°C.

[0105] Aspect 5. The varnish composition of any one of the preceding aspects, wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: greater than or equal to 99 wt%, more preferably greater than or equal to 99.5 wt% of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions; 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions; 0.0001 to 0.5 wt%, or 0.1 to 0.5 wt%, or 0.25 to 0.5 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 0.5 wt%, or 0.1 to 0.5 wt%, or 0.25 to 0.5 wt% of residual 4,4'-BPA diacid; and 0.00001 to 0.4 wt%, or 0.01 to 0.5 wt%, or 0.01 to 0.5 wt%, or 0.05 to 0.5 wt% of residual 4,4'-BPA imi de-anhydride, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition.

[0106] Aspect 6. The varnish composition of any one of the preceding aspects, wherein the organic diamine comprises one or more diamines each independently of formula

H₂N-R-NH₂ wherein R is a C_6-30 aromatic or heteroaromatic hydrocarbon, a straight or branched chain C_4.20 alkylene, a C_3.8 cycloalkylene, or a halogenated derivative thereof; preferably wherein R is a divalent group of one or more of formulas:

aryl, -C_yH_2y- wherein y is an integer from 1 to 5 or a halogenated derivative thereof, or -(C₆H_I0)_z- wherein z is an integer from 1 to 4; preferably wherein the organic diamine is 1,4-butane diamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9- nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine, 1,18-octadecanediamine, 3- methylheptamethylenedi amine, 4,4-dimethylheptamethylenediamine, 4- methylnonamethylenediamine, 5-methylnonamethylenediamine, 2,5- dimethylhexamethylenedi amine, 2,5-dimethylheptamethylenediamine, 2, 2- dimethylpropylenediamine, N-methyl-bis (3-aminopropyl) amine, 3-methoxyhexamethylenediamine, l,2-bis(3-aminopropoxy) ethane, l,3-bis(4-aminophenoxy)benzene, bis(3-aminopropyl) sulfide, 1,4- cyclohexanediamine, bis-(4-aminocyclohexyl) methane, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, m-xylylenediamine, p-xylylenediamine, 2-methyl-4,6- diethyl-l,3-phenylene-diamine, 5-methyl-4,6-diethyl-l,3-phenylene-diamine, benzidine, 3,3'- dimethylbenzidine, 3,3 '-dimethoxybenzi dine, 1,5-diaminonaphthalene, 9,10-dimethylanthracene, 4,4'-methylenedianiline, 4,4'-oxydianibne, 4,4'-azodianiline, bis(4-aminophenyl) methane, bis(2- chloro-4-amino-3,5-diethylphenyl) methane, bis(4-aminophenyl) propane, 2,4-bis(p-amino-t-butyl) toluene, bis(p-amino-t-butylphenyl) ether, bis(p-methyl-o-aminophenyl) benzene, bis(p-methyl-o- aminopentyl) benzene, l,3-bis(4-aminophenoxy)benzene, l,3-diamino-4-isopropylbenzene, bis(4- aminophenyl) sulfide, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'- diaminodiphenylsulfone, bis(4-aminophenyl) ether, 2,6-diamino, 3,3'-diaminobenzophenone, 4,4'- diaminobenzophenone, a regioisomer thereof, a C alkylated or poly(Ci_4)alkylated derivative thereof, a halogenated derivative thereof, or a combination thereof; more preferably wherein the organic diamine is meta-phenylene diamine, para-phenylene diamine, ortho-phenylene diamine, 4,4'- diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'- oxydianibne, l,3-bis(4-aminophenoxy)benzene, or a combination thereof; even more preferably wherein the organic diamine is m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, or a combination thereof.

[0107] Aspect 7. The varnish composition of any one of the preceding aspects, wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione is made by a method comprising: hydrolyzing a 4,4'-BPADA-bisimide to form a corresponding 4,4'-BPADA tetraacid tetrasalt; contacting the 4,4'-BPADA tetraacid tetrasalt with a mineral acid to form a corresponding 4,4'-BPADA tetraacid; contacting the 4,4'-BPADA tetraacid with a halogenated solvent to form a reaction mixture, optionally wherein the halogenated solvent comprises ortho-dichlorobenzene, para- dichlorobenzene, meta-dichlorobenzene, trichlorobenzene, or a combination thereof; heating the reaction mixture to a temperature effective to form the corresponding 5,5 ’-[1- methylethybdene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione from the 4,4'-BPADA tetraacid, optionally in the presence of a mineral acid; and isolating the 5,5’-[l-methylethylidene)bis(4,l- phenyleneoxy)bis-l,3-isobenzofurandione from the reaction mixture; optionally wherein the method is carried out in the absence of an organic acid, an organic acid anhydride, or both.

[0108] Aspect 8. The varnish composition of any one of the preceding aspects, wherein the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N- dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, N-cyclohexylpyrrolidinone, N- methylcaprolactam, l,3-dimethyl-2-imidazolidone, 1 ,2-dimethoxy ethane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, g-butyrolactone, g-caprolactone, dimethylsulfoxide, benzophenone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diglyme, triglyme, tetraglyme, N,N- dimethylethyleneurea, N,N-dimethylpropyleneurea, tetramethylurea, propylene glycol phenyl ether, anisole, veratrole, o-dichlorobenzene, chlorobenzene, trichloroethane, methylene chloride, chloroform, pyridine, picoline, ethyl lactate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate, ethyl carbitol acetate, propylene carbonate, sulfolane, an ionic liquid, or a combination thereof.

[0109] Aspect 9. An article manufactured from the varnish composition of any one of the preceding aspects, preferably wherein the article is a fiber, a layer, a coating, a cast article, a prepreg, a composite, or a laminate.

[0110] Aspect 10. The article of aspect 9, wherein the article is a composite comprising: a porous base material, preferably a fibrous preform comprising woven or non-woven glass fabric, a fiberglass fabric, or a carbon fiber, wherein the porous base material is coated or impregnated with the varnish composition of any one of aspects 1 to 8; preferably wherein the article is a prepreg, a sheet, a wire coating, a molded article, or a compression article.

[0111] Aspect 11. The article of aspect 9, wherein the article is a flexible metal-clad laminate comprising: a conductive metal layer, preferably wherein the conductive metal layer is copper, zinc, tin, brass, chromium, molybdenum, nickel, cobalt, aluminum, stainless steel, iron, gold, silver, platinum, titanium, an alloy thereof, or a combination thereof; the varnish composition of any one of aspects 1 to 8 at least partially disposed on the conductive metal layer; and optionally a supporting metal matrix layer, wherein the supporting metal matrix layer is disposed on a side opposite the conductive metal layer, preferably wherein the supporting metal matrix layer is a thermally conductive metal layer that is electrically isolated from the conductive metal layer, more preferably wherein the thermally conductive metal is aluminum, boron nitride, aluminum nitride, copper, iron, steel, or a combination thereof, preferably wherein the conductive metal layer is patterned to provide a printed circuit board, more preferably wherein the printed circuit board has a sheet, a tube, or a rod shape.

[0112] Aspect 12. A cured product of the varnish composition of any one of aspects 1 to 8, comprising: a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; or a thickness of 0.1 to 1,000 micrometers, or 0.1 to 500 micrometers, or 0.1 to 250 micrometers; or a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23°C, as determined by dielectric spectroscopy; or a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measure at 10 GHz and 23 °C, as determined by dielectric spectroscopy; or a combination thereof. [0113] Aspect 13. A method of manufacturing an article from the varnish composition of any one of aspects 1 to 9, the method comprising: disposing the varnish composition on a substrate; and curing the varnish composition to form the article; preferably wherein the article is a fiber, a layer, a coating, a cast article, a prepreg, a composite, or a laminate.

[0114] Aspect 14. The method of aspect 14, comprising: forming a layer comprising the varnish composition of any one of aspects 1 to 10 on a substrate; removing the solvent from the layer to provide a primer layer; forming a second layer comprising a ceramic, a fluoropolymer, a thermosetting polymer, or a combination thereof on the primer layer to provide the multilayer article; and optionally thermally treating the multilayer article to cure the thermosetting polymer; wherein the second layer optionally further comprises the varnish composition of any one of aspects 1 to 10, and forming the layer further comprises removing the solvent from the second layer; wherein the ceramic is A1₂0₃, Ti0₂, Zr0₂, Cr₂0₃, Si0₂, MgO, BeO; Y₂0₃, A1₂0₃-SI0₂, MgO-Zr0₂, SiC, WC, B C, TiC, Si₃N₄, TiN, BN, AIN, TiB, ZrB₂, or a combination thereof; the fluoropolymer is polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinylether copolymer, tetrafluoroethylene- hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, poly vinyli dene fluoride, or a combination thereof; and the thermosetting polymer is epoxy resin, polyester resin, polyimide resin, bis-maleimide resin, cyanate ester resin, vinyl resin, benzoxazine resin, benzocyclobutene resin, phenol resin, urea resin, melamine-formaldehyde resin, urea-formaldehyde latex, xylene resin, diallylphthalate resin, aniline resin, furan resin, polyurethane, mineral filled silicone, or a combination thereof.

[0115] Aspect 15. A varnish composition, comprising: a polyamic acid comprising structural units derived from reaction of 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5,5’ -[1- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: greater than or equal to 99.5 wt% of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione; 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions; 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions; 0.0001 to 0.5 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 0.5 wt% of residual 4,4'- BPA diacid; and 0.00001 to 0.5 wt% of residual 4,4'-BPA imi de-anhydride, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition, wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3-isobenzofurandione composition is made by a method comprising: hydrolyzing a 4,4'-BPADA- bisimide to form a corresponding 4,4'-BPADA tetraacid tetrasalt; contacting the 4,4'-BPADA tetraacid tetrasalt with a mineral acid to form a corresponding 4,4'-BPADA tetraacid; contacting the 4,4'-BPADA tetraacid with a halogenated solvent to form a reaction mixture, optionally wherein the halogenated solvent comprises ortho-dichlorobenzene, para-dichlorobenzene, meta-dichlorobenzene, trichlorobenzene, or a combination thereof; heating the reaction mixture to a temperature effective to form the corresponding 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione from the 4,4'-BPADA tetraacid, optionally in the presence of a mineral acid; and isolating the 5,5’- [l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione from the reaction mixture; optionally wherein the method is carried out in the absence of an organic acid, an organic acid anhydride, or both, and wherein a cured product of the varnish composition has a glass transition temperature of 190 to 260°C, as determined by DSC, and two or more of: a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23 °C, as determined by dielectric spectroscopy; or a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measured at 10 GHz and 23 °C, as determined by dielectric spectroscopy.

[0116] Aspect 16. The varnish composition of aspect 15, wherein the varnish composition has a dynamic viscosity that is a greater than a dynamic viscosity of a comparable varnish composition that is prepared from an 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition that includes less than 99.5 wt% of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione, based on the total weight of the 5,5 ’ -[ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition, wherein the dynamic viscosities are determined at a solids content of 10 wt% in l-methylpyrrolidin-2-one at 25°C.

[0117] Aspect 17. The varnish composition of any one of the preceding aspects, wherein a film derived from the varnish composition has a T_g that is a less than a T_g of a comparable varnish composition that is prepared from an 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition that includes less than 99.5 wt% of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione, based on the total weight of the 5,5 ’ -[ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition, wherein the dynamic viscosities are determined at a solids content of 10 wt% in l-methylpyrrolidin-2-one at 25°C.

[0118] Aspect 18. The varnish composition of any one of the preceding aspects, wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 0.0001 to 1 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 1 wt% of residual 4,4'-BPA diacid; and 0.00001 to 0.1 wt% of residual 4,4'-BPA imide-anhydride, wherein each amount is based on the total weight of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione composition, and wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises greater than or equal to 99.5 wt% of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione.

[0119] Aspect 18. The varnish composition of any one of the preceding aspects, wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; and 0.00001 to 0.1 wt% of residual 4,4'-BPA imide-anhydride, based on the total weight of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition, wherein the 5,5’- [l-methylethybdene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises greater than or equal to 99.5 wt% of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione.

[0120] Aspect 19. A varnish composition comprising apolyamic acid comprising structural units derived from reaction of 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5,5’ -[1- methylethybdene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’- [l-methylethybdene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 25 ppm or less, or 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions; 50 ppm or less, or 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions; 0.0001 to 1 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 1 wt% of residual 4,4'-BPA diacid; and 0.00001 to 0.1 wt% of residual 4,4'-BPA imide-anhydride, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition, wherein a dynamic viscosity of the varnish composition is 20,000 to 120,000 cP, or 20,000 to 80,000 cP, or 40,000 to 80,000 cP, as determined at a solids content of 10 wt% in l-methylpyrrolidin-2-one at 25°C, and wherein a cured product of the varnish composition has a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by differential scanning calorimetry, preferably wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition comprises greater than or equal to 99.5 wt% of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione.

[0121] Aspect 20. A varnish composition comprising apolyamic acid comprising structural units derived from reaction of 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5,5’ -[1- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition comprises: the 5,5’- [l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione; 0.00001 to 0.1 wt% of residual 4,4'-BPA imide-anhydride, based on the total weight of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition, wherein a dynamic viscosity of the varnish composition is 20,000 to 120,000 cP, or 20,000 to 80,000 cP, or 40,000 to 80,000 cP, as determined at a solids content of 10 wt% in l-methylpyrrolidin-2-one at 25°C, and wherein a cured product of the varnish composition has a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by differential scanning calorimetry, preferably wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition comprises greater than or equal to 99.5 wt% of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione.

[0122] The compositions, methods, and articles can alternatively comprise, consist of, or consist essentially of, any appropriate materials, steps, or components herein disclosed. The compositions, methods, and articles can additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any materials (or species), steps, or components, that are otherwise not necessary to the achievement of the function or objectives of the compositions, methods, and articles.

[0123] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., ranges of “up to 25 wt.%, or, more specifically, 5 wt.% to 20 wt.%”, is inclusive of the endpoints and all intermediate values of the ranges of “5 wt.% to 25 wt.%,” etc.). “Combinations” is inclusive of blends, mixtures, alloys, reaction products, and the like. The terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” and “the” do not denote a limitation of quantity and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. “Or” means “and/or” unless clearly stated otherwise. Reference throughout the specification to “some aspects”, “an aspect”, and so forth, means that a particular element described in connection with the aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various aspects. A “combination thereof’ is open and includes any combination comprising at least one of the listed components or properties optionally together with a like or equivalent component or property not listed.

[0124] Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

[0125] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this application belongs. All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference. [0126] Compounds are described using standard nomenclature. For example, any position not substituted by any indicated group is understood to have its valency filled by a bond as indicated, or a hydrogen atom. A dash

that is not between two letters or symbols is used to indicate a point of attachment for a substituent. For example, -CHO is attached through carbon of the carbonyl group.

[0127] The term “hydrocarbon” refers to any compound, group, or substituent that includes carbon and hydrogen. “Aliphatic” means a non-aromatic hydrocarbon group. “Alkyl” means a branched or straight chain, unsaturated aliphatic hydrocarbon group. “Cycloalkyl” means a mono- or polycyclic alkyl group, wherein all ring members are carbon. “Alkenyl” means a straight or branched chain, monovalent hydrocarbon group having at least one carbon-carbon double bond. “Alkoxy” means an alkyl group that is linked via an oxygen (i.e., alkyl-O-). “Alkylene” means a straight or branched chain, saturated, divalent aliphatic hydrocarbon group. “Cycloalkylene” means a divalent cycloalkyl group, wherein all ring members are carbon. “Cycloalkenyl” means a mono- or polycyclic alkenyl group, wherein all ring members are carbon. “Aryl” means a mono- or polycyclic aromatic hydrocarbon group, wherein all ring members are carbon. “Arylene” means a divalent aryl group. “Alkylaryl” means an aryl group substituted with an alkyl group. “Arylalkyl” means an alkyl group substituted with an aryl group. The prefix “halo” means a group or compound including one more halogen substituents that can be the same or different. The prefix “hetero” means that the compound or group includes at least one ring member that is a heteroatom (e.g., 1, 2, or 3 heteroatom(s)), wherein the heteroatom(s) are each independently N, O, S, Si, or P.

[0128] Unless substituents are otherwise specifically indicated, each of the foregoing groups can be unsubstituted or substituted, provided that the substitution does not significantly adversely affect synthesis, stability, or use of the compound. “Substituted” means that the compound, group, or atom is substituted with at least one (e.g., 1, 2, 3, or 4) substituents that can each independently be a nitro (-NO₂), cyano (-CN), hydroxy (-OH), halogen, thiol (-SH), thiocyano (-SCN), Ci-6 alkyl, C_2-6 alkenyl, C_2-6 alkynyl, Ci-6 haloalkyl, C_1-9 alkoxy, Ci-6 haloalkoxy, C_3-12 cycloalkyl, C_5-18 cycloalkenyl, C_6-12 aryl, C_7-13 arylalkyl (e.g., benzyl), C_7-12 alkylaryl (e.g., toluyl), C_4-12 heterocycloalkyl, C_3-12 heteroaryl, Ci-6 alkyl sulfonyl (-S(=0)2-alkyl), C_6-12 arylsulfonyl (-S(=0)2- aryl), or tosyl (CH3C6H4SO2-), instead of hydrogen, provided that the substituted atom’s normal valence is not exceeded. The number of carbon atoms indicated in a group is exclusive of any substituents. For example -CFI₂CFI₂CN is a C₂ alkyl group substituted with a cyano group.

[0129] While particular aspects have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.

Claims

CLAIMS What is claimed is:

1. A varnish composition, comprising: a polyamic acid comprising structural units derived from reaction of a 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition comprises: the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione;

25 ppm or less, or 0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions;

50 ppm or less, or 0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions;

0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of residual 4,4'-BPA tetraacid;

0.0001 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of residual 4,4'-BPA diacid; and

0.00001 to 4 wt%, or 0.01 to 4 wt%, or 0.01 to 2 wt%, or 0.05 to 1 wt% of residual 4,4'-BPA imide-anhydride, wherein each amount is based on the total weight of the 5,5 ’-[1- methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition, and wherein a dynamic viscosity of the varnish composition is 20,000 to 120,000 cP, or 20,000 to 80,000 cP, or 40,000 to 80,000 cP, as determined at a solids content of 10 wt% in 1- methylpyrrolidin-2-one at 25°C, and wherein a cured product of the varnish composition has a glass transition temperature of 150 to 300°C, or 190 to 300°C, or 200 to 300°C, or 210 to 300°C, as determined by differential scanning calorimetry, preferably wherein the 5,5’-[l-methylethylidene)bis(4,l-phenyleneoxy)bis-l,3- isobenzofurandione composition comprises greater than or equal to 99 wt%, more preferably greater than or equal to 99.5 wt% of the 5,5’-[l-methylethylidene)bis(4,l- pheny 1 eneoxy )bi s- 1 , 3 -i sobenzofurandione.

2 The varnish composition of claim 1, wherein the 5,5’-[l-methylethylidene)bis(4,l- phenyleneoxy)bis- 1,3 -isobenzofurandione composition comprises: the 5 , 5 ’ - [ 1 -methylethybdene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione;

0.0002 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of the residual 4,4'- BPA tetraacid and the residual 4,4'-BPA diacid combined,

0.01 to 50 ppm, or 0.01 to 25 ppm of sulfate ions;

0.01 to 25 ppm, or 0.01 to 10 ppm of sodium ions; and 0.01 to 25 ppm, or 0.01 to 10 ppm of chloride ions, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l- pheny 1 eneoxy )bi s- 1 , 3 -i sobenzofurandione composition.

3. The varnish composition of claim 1 or 2, wherein the 5,5 ’-[1- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione comprises: the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyl eneoxy )bis- 1 ,3 -isobenzofurandione;

15 ppm or less, or 0.01 to 15 ppm, or 0.01 to 10 ppm of sulfate ions;

10 ppm or less, or 0.01 to 10 ppm, or 0.01 to 5 ppm of sodium ions;

5 ppm or less, or 0.01 to 5 ppm, or 0.01 to 2 ppm of chloride ions;

2 ppm or less, or 0.01 to 2 ppm, or 0.01 to 1 ppm of nitrate ions; and 2 ppm or less, or 0.01 to 2 ppm, or 0.01 to 1 ppm of nitrite ions, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l- pheny 1 eneoxy )bi s- 1 , 3 -i sobenzofurandione composition.

4. The varnish composition of any one of the preceding claims, wherein the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition comprises: the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyl eneoxy )bis- 1 ,3 -isobenzofurandione; 0.0002 to 10 wt%, or 0.1 to 10 wt%, or 0.25 to 2 wt%, or 0.25 to 1 wt% of the 4,4'- BPA tetraacid and 4,4'-BPA diacid combined;

0.01 to 50 ppm, or 0.01 to 25 ppm of sulfate ions;

0.01 to 25 ppm, or 0.01 to 10 ppm of sodium ions; and

0.01 to 25 ppm, or 0.01 to 10 ppm of chloride ions, wherein each amount is based on the total weight of the 5,5 ’-[1- methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition.

5. The varnish composition of any one of the preceding claims, wherein the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione composition comprises: greater than or equal to 99 wt%, more preferably greater than or equal to 99.5 wt% of the 5,5 ’ -[ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione;

0.01 to 25 ppm each of sodium ions, potassium ions, calcium ions, zinc ions, aluminum ions, titanium ions, iron ions, chromium ions, molybdenum ions, nickel ions, and phosphorus ions;

0.01 to 50 ppm each of phosphate ions, sulfate ions, chloride ions, nitrate ions, and nitrite ions;

0.0001 to 0.5 wt%, or 0.1 to 0.5 wt%, or 0.25 to 0.5 wt% of residual 4,4'-BPA tetraacid; 0.0001 to 0.5 wt%, or 0.1 to 0.5 wt%, or 0.25 to 0.5 wt% of residual 4,4'-BPA diacid; and 0.00001 to 0.4 wt%, or 0.01 to 0.5 wt%, or 0.01 to 0.5 wt%, or 0.05 to 0.5 wt% of residual 4,4'-BPA imide-anhydride, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l- pheny 1 eneoxy )bi s- 1 , 3 -i sobenzofurandione composition.

6. The varnish composition of any one of the preceding claims, wherein the organic diamine comprises one or more diamines each independently of formula

H2N-R-NH2 wherein R is a C_6-30 aromatic or heteroaromatic hydrocarbon, a straight or branched chain C_4.20 alkylene, a C3.8 cycloalkylene, or a halogenated derivative thereof; preferably wherein R is a divalent group of one or more of formulas:

wherein Q¹ is -0-, -S-, -C(O)-, -N=N-, -SO₂-, -SO-, -P(R^a)(=0)- wherein R^a is a Ci-g alkyl or C_6-12 aryl, -C_yH_2y- wherein y is an integer from 1 to 5 or a halogenated derivative thereof, or -(C₆H_I0)_z- wherein z is an integer from 1 to 4; more preferably wherein the organic diamine is 1,4-butane diamine, 1,5-pentanediamine, 1,6- hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1 , 10-decanediamine,

1,12-dodecanediamine, 1,18-octadecanediamine, 3-methylheptamethylenediamine, 4,4- dimethylheptamethylenedi amine, 4-methylnonamethylenediamine, 5-methylnonamethylenediamine,

2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 2, 2- dimethylpropylenediamine, N-methyl-bis (3-aminopropyl) amine, 3-methoxyhexamethylenediamine, l,2-bis(3-aminopropoxy) ethane, l,3-bis(4-aminophenoxy)benzene, bis(3-aminopropyl) sulfide, 1,4- cyclohexanediamine, bis-(4-aminocyclohexyl) methane, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, m-xylylenediamine, p-xylylenediamine, 2-methyl-4,6- diethyl-l,3-phenylene-diamine, 5-methyl-4,6-diethyl-l,3-phenylene-diamine, benzidine, 3,3'- dimethylbenzidine, 3,3 '-dimethoxybenzi dine, 1,5-diaminonaphthalene, 9,10-dimethylanthracene, 4,4'-methylenedianiline, 4,4'-oxydianiline, 4,4'-azodianiline, bis(4-aminophenyl) methane, bis(2- chloro-4-amino-3,5-diethylphenyl) methane, bis(4-aminophenyl) propane, 2,4-bis(p-amino-t-butyl) toluene, bis(p-amino-t-butylphenyl) ether, bis(p-methyl-o-aminophenyl) benzene, bis(p-methyl-o- aminopentyl) benzene, l,3-bis(4-aminophenoxy)benzene, l,3-diamino-4-isopropylbenzene, bis(4- aminophenyl) sulfide, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'- diaminodiphenylsulfone, bis(4-aminophenyl) ether, 2,6-diamino, 3,3'-diaminobenzophenone, 4,4'- diaminobenzophenone, a regioisomer thereof, a C alkylated or poly(Ci_4)alkylated derivative thereof, a halogenated derivative thereof, or a combination thereof; preferably wherein the organic diamine is meta-phenylene diamine, para-phenylene diamine, ortho-phenylene diamine, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'- diaminodiphenylsulfone, 4, 4'-oxy dianiline, l,3-bis(4-aminophenoxy)benzene, or a combination thereof; more preferably wherein the organic diamine is m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, or a combination thereof.

7. The varnish composition of any one of the preceding claims, wherein the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition is made by a method comprising: hydrolyzing a 4,4'-BPADA-bisimide to form a corresponding 4,4'-BPADA tetraacid tetrasalt; contacting the 4,4'-BPADA tetraacid tetrasalt with a mineral acid to form a corresponding 4,4'-BPADA tetraacid; contacting the 4,4'-BPADA tetraacid with a halogenated solvent to form a reaction mixture, optionally wherein the halogenated solvent comprises ortho-dichlorobenzene, para-dichlorobenzene, meta-dichlorobenzene, trichlorobenzene, or a combination thereof; heating the reaction mixture to a temperature effective to form the corresponding 5,5 ’-[1- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione from the 4,4'-BPADA tetraacid, optionally in the presence of a mineral acid; and isolating the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione from the reaction mixture; optionally wherein the method is carried out in the absence of an organic acid, an organic acid anhydride, or both.

8. The varnish composition of any one of the preceding claims, wherein the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N- dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, N-cyclohexylpyrrolidinone, N- methylcaprolactam, l,3-dimethyl-2-imidazolidone, 1 ,2-dimethoxy ethane, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, g-butyrolactone, g-caprolactone, dimethylsulfoxide, benzophenone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diglyme, triglyme, tetraglyme, N,N- dimethylethyleneurea, N,N-dimethylpropyleneurea, tetramethylurea, propylene glycol phenyl ether, anisole, veratrole, o-dichlorobenzene, chlorobenzene, trichloroethane, methylene chloride, chloroform, pyridine, picoline, ethyl lactate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate, ethyl carbitol acetate, propylene carbonate, sulfolane, an ionic liquid, or a combination thereof.

9. An article manufactured from the varnish composition of any one of the preceding claims, preferably wherein the article is a fiber, a layer, a coating, a cast article, a prepreg, a composite, or a laminate.

10. The article of claim 9, wherein the article is a composite comprising: a porous base material, preferably a fibrous preform comprising woven or non-woven glass fabric, a fiberglass fabric, or a carbon fiber, wherein the porous base material is coated or impregnated with the varnish composition of any one of claims 1 to 8; preferably wherein the article is a prepreg, a sheet, a wire coating, a molded article, or a compression article.

11. The article of claim 9, wherein the article is a flexible metal-clad laminate comprising: a conductive metal layer, preferably wherein the conductive metal layer is copper, zinc, tin, brass, chromium, molybdenum, nickel, cobalt, aluminum, stainless steel, iron, gold, silver, platinum, titanium, an alloy thereof, or a combination thereof; the varnish composition of any one of claims 1 to 8 at least partially disposed on the conductive metal layer; and optionally a supporting metal matrix layer, wherein the supporting metal matrix layer is disposed on a side opposite the conductive metal layer, preferably wherein the supporting metal matrix layer comprises a thermally conductive metal that is electrically isolated from the conductive metal layer, more preferably wherein the thermally conductive metal is aluminum, boron nitride, aluminum nitride, copper, iron, steel, or a combination thereof, preferably wherein the conductive metal layer is patterned to provide a printed circuit board, more preferably wherein the printed circuit board has a sheet, a tube, or a rod shape.

12. A cured product of the varnish composition of any one of claims 1 to 8, comprising: a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4

N/mm, as determined according to IPC 2.4.8; or a thickness of 0.1 to 1,000 micrometers, or 0.1 to 500 micrometers, or 0.1 to 250 micrometers; or a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23°C, as determined by dielectric spectroscopy; or a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measure at 10 GHz and 23 °C, as determined by dielectric spectroscopy; or a combination thereof.

13. A method of manufacturing an article from the varnish composition of any one of claims 1 to 8, the method comprising: disposing the varnish composition on a substrate; and curing the varnish composition to form the article; preferably wherein the article is a fiber, a layer, a coating, a cast article, a prepreg, a composite, or a laminate.

14. The method of claim 13, comprising: forming a first layer comprising the varnish composition on the substrate; removing the solvent from the first layer to provide a primer layer; and forming a second layer comprising a ceramic, a fluoropolymer, a thermosetting polymer, or a combination thereof on the primer layer to provide a multilayer article, wherein the second layer optionally further comprises the varnish composition, wherein the ceramic is AI₂O₃, T1O₂, ZrC>₂, Cr₂0₃, S1O₂, MgO, BeO; Y₂O₃, AI₂O_{3 —} S1O₂,

MgO — Zr0₂, SiC, WC, B₄C, TiC, S1₃N₄, TiN, BN, AIN, TiB, ZrB₂, or a combination thereof, wherein the fluoropolymer is polytetrafluoroethylene, tetrafluoroethylene- perfluoroalkylvinylether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, or a combination thereof, and wherein the thermosetting polymer is epoxy resin, polyester resin, polyimide resin, bis- maleimide resin, cyanate ester resin, vinyl resin, benzoxazine resin, benzocyclobutene resin, phenol resin, urea resin, melamine-formaldehyde resin, urea-formaldehyde latex, xylene resin, diallylphthalate resin, aniline resin, furan resin, polyurethane, mineral filled silicone, or a combination thereof.

15. A varnish composition, comprising: a polyamic acid comprising structural units derived from reaction of 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis-l,3-isobenzofurandione composition with an organic diamine; and a solvent, wherein the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition comprises: greater than or equal to 99 wt%, or greater than or equal to 99.5 wt% of the 5,5’-[l- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione;

0.0001 to 0.5 wt% of residual 4,4'-BPA tetraacid;

0.0001 to 0.5 wt% of residual 4,4'-BPA diacid; and 0.00001 to 0.5 wt% of residual 4,4'-BPA imi de-anhydride, wherein each amount is based on the total weight of the 5,5’-[l-methylethylidene)bis(4,l- pheny 1 eneoxy )bi s- 1 , 3 -i sobenzofurandione composition, wherein the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione composition is made by a method comprising: hydrolyzing a 4,4'-BPADA-bisimide to form a corresponding 4,4'-BPADA tetraacid tetrasalt; contacting the 4,4'-BPADA tetraacid tetrasalt with a mineral acid to form a corresponding 4,4'-BPADA tetraacid; contacting the 4,4'-BPADA tetraacid with a halogenated solvent to form a reaction mixture, optionally wherein the halogenated solvent comprises ortho-dichlorobenzene, para- dichlorobenzene, meta-dichlorobenzene, trichlorobenzene, or a combination thereof; heating the reaction mixture to a temperature effective to form the corresponding 5,5 ’-[1- methylethylidene)bis(4,l-phenyleneoxy)bis- 1,3 -isobenzofurandione from the 4,4'- BPADA tetraacid, optionally in the presence of a mineral acid; and isolating the 5 , 5 ’ - [ 1 -methylethylidene)bis(4, 1 -phenyleneoxy)bis- 1 ,3 -isobenzofurandione from the reaction mixture; optionally wherein the method is carried out in the absence of an organic acid, an organic acid anhydride, or both, and wherein a cured product of the varnish composition has a glass transition temperature of 190 to 260°C, as determined by DSC, and two or more of: a peel strength of greater than 1.3 N/mm, or greater than 1.35 N/mm, or greater than 1.4 N/mm, as determined according to IPC 2.4.8; a dielectric constant of 2 to 5, or 2.5 to 4, or 2.8 to 3.2 when measured at 10 GHz and 23 °C, as determined by dielectric spectroscopy; or a dissipation factor of 0.00001 to 0.01, or 0.001 to 0.01, or 0.001 to 0.008 when measured at 10 GHz and 23°C, as determined by dielectric spectroscopy.