Imide Structure Research Articles

Preparation and properties of novel processable polyimides derived fromN,N-bis(isocyanatoalkyl)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimides

Two diisocyanate monomers containing methylene groups and built-in imide structure have been prepared from the parent diacids via the Curtius–Weinstock rearrangement. Polyimides have been synthesized by solution polymerization of these isocyanates with pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and hexafluoroisopropylidene-2,2-bis(phthalic-anhydride) (6FDA). All monomers and polymers were characterized by conventional methods, and the physical properties of the polymers, including solution viscosity, solubility, thermal stability and thermal behaviour, were studied. © 2000 Society of Chemical Industry

Low-Temperature Route to 1, 2-Benzoylenebenzimidazole Ladder Structure

Low-temperature catalytic conversion of N-( o-aminophenyl)phthalamic acid (I) was studied as a model reaction for the synthesis of ladder poly(aroylenebenzimidazole)s. The treatment of I with acetic anhydride/pyridine or trifluoroacetic anhydride resulted in the selective and quantitative cyclodehydration to yield either imide or isoimide structures respectively. The imidization was accompanied by acylation of the ortho amino group to form lateral acetamide or trifluoroacetamide substitutes. Thermodynamically unstable N-( o-trifluoroacetamidophenyl)phthalisoimide (III) underwent secondary cyclization to yield ladder 1, 2-benzoylenebenzimidazole (V) between 130 and 150 °C. The conversion of this reaction did not exceed 35% because it competed with the thermal isomerization of III to the stable N-( o-trifluoroacetamido-phenyl)phthalimide (IV). The cyclization of N-( o-trifluoroacetamidophenyl)phthalisoimide (III) was found to be possible even at room temperature. The formation of 30–35% of the ladder 1, 2-benzoylene-benzimidazole (V) was observed after III was dissolved in DMF and stored at room temperature for 4–10 h. This also was accompanied by the catalytic isoimide-to-imide isomerization. The obtained data may be useful for the further development of novel low-temperature approaches to the synthesis of ladder poly(aroylenebenzimidazole)s. Synthesis of aromatic polyimides and polyisoimides with lateral alkylamide or trifluoroalkylamide from available aromatic dianhydrides and tetraamines may also be of practical interest.

Synthesis and characterization of new soluble and thermostable polyimides via novel diisocyanates

A facile synthesis of two novel diisocyanates containing methylene groups and preformed imide structure is described. Furthermore, six thermally stable and soluble polyimides were synthesized by polycondensation of these two diisocyanates with pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and hexafluoroisopropylidene-2,2-bis-(phthalic anhydride) (6FDA) in N,N-dimethyl acetamide. All monomers and polymers were characterized by conventional methods and their physical properties such as solution viscosity, solubility properties, thermal stability and thermal behaviour were studied. © 1999 Society of Chemical Industry

Synthesis and characterization of new soluble and thermostable polyimides via novel diisocyanates

A facile synthesis of two novel diisocyanates containing methylene groups and preformed imide structure is described. Furthermore, six thermally stable and soluble polyimides were synthesized by polycondensation of these two diisocyanates with pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and hexafluoroisopropylidene-2,2-bis-(phthalic anhydride) (6FDA) in N,N-dimethyl acetamide. All monomers and polymers were characterized by conventional methods and their physical properties such as solution viscosity, solubility properties, thermal stability and thermal behaviour were studied. © 1999 Society of Chemical Industry

FTIR spectroscopic studies of interfacial reactions between amino functionalized silicon surfaces and molten maleic anhydride copolymers

The interactions of two reactive maleic anhydride copolymers, a styrene maleic anhydride copolymer and an alternating copolymer of malic anhydride and α-olefin side chains, with amino-functionalized surfaces were studied by means of FTIR-ATR spectroscopy. The interfacial processes were detected at a planar surface of a thermally oxidized silicon as internal reflecting element. This ATR element can be understood as a model for a glass fiber which is used as reinforcing material in polymer matrices. A typical glass fiber coupling agent, γ-aminopropyltriethoxysilane (γ-APS), was used to functionalize the silicon dioxide layer. It was found that the amino groups of the amino siloxane network layer, which were obtained by a coating procedure with γ-APS, react with the anhydride groups of the copolymer melt to form amic acid structures and imide structures depending on the chemical composition of the copolymers and the temperature.

Nonequilibrium Structures of Dialkyl Pyromellitates Monolayers and their LB Network Films Containing Pyromellitimide Linkage

Two kinds of pyromellitates with different alkyl chains (C 12 and C18) showed characteristic monolayer structures by Brewster angle microscopy, and their Langmuir-Blodgett (LB) films were characterized by FT-IR spectroscopy. The star-like structures on pure water subphase were smoothened on aq. poly (allylamine) subphase. The polyion-complexed monolayer of pyromellitates with poly(allylamine) was transferable on calcium fluoride substrate. The resulting LB films could be networked by heat treatment, and imide structures were produced in the network LB films.

Anionic Polymerization of N-Phenylitaconimide

N-Phenylitaconimide (N-PII) can be readily polymerized with basic initiators that involve carbide, nitride, and oxide anions such as sec-butyllithium, lithium diethylamide, and alkali metal tert-butoxide. Poly(N-PII) was obtained in 84, 73, and 78% yields with sec-butyllithium, lithium diethylamide, and lithium tert-butoxide, respectively, in THF at 0 °C for 3 h polymerization. The effect of countercation size on the anionic polymerization rate of N-PII (1,1-disubstituted ethylene type monomer with cyclic imide structure) with alkali metal tert-butoxides is inverse to that of N-phenylmaleimide (N-PMI) (1,2-disubstituted ethylene type one); i.e., it was observed that the polymerization rate increased as the ion radius of a countercation decreased. NMR spectroscopic data and molecular orbital calculations suggest that the anionic polymerization of N-PII took place only at the vinylidene group and no appreciable side reaction would occur. In the case of using the initiators with Li+ as a countercation, the molecular weight distribution of poly(N-PII) is apparently unimodal and polydispersity is relatively small. The mechanism of the anionic polymerization of N-PII was discussed in detail. The thermal properties of poly(N-PII) obtained were also presented: it possessed a Tg under its decomposition temperature and could form a film by the cast method while those could not be observed for poly(N-PMI).

Preparation and characterization of polymides derived from bis(methoxycarbonyl)terephthaloyl chloride by interfacial condensation

AbstractA series of polyimides was synthesized by interfacial condensation of bis(methoxycarbonyl)terephthaloyl choride (1) with aromatic diamines and polycyclic aliphatic diamines. 1 (mixed isomers) was synthesized from pyromellitic dianhydride and contains about 60% para isomers and 40% meta isomer. The poly(amic ester)s 3 had inherent viscosities of 0.85–0.24 dL/g. All the poly(amic ester)s were soluble in NMP, DMAc, DMF, and DMSO, except for the polymer prepared from diamantane‐1,6‐diamine. Through thermal treatment the poly(amic‐ester)s formed imide structures. All the polyimides and poly(amic ester)s were amorphous due to X‐ray diffraction studies. The glass transition temperatures of these polyimides were in the range of 255–340°C, and the 5% weight loss temperatures were between 485 and 640 °C in nitrogen atmosphere. The polyimides (4c and 4d) with polycyclic aliphatic diamines such as adamantane‐1,3‐diamine and diamantane‐1,6‐diamine had good thermal stability, with a temperature of 5% weight loss above 485°C. The polyimides 4c and 4d also had high glass transition temperature of 340°C and 300°C, respectively.

Curing reaction of diglycidylesters containing alicyclic imide structures with anhydrides and amines as hardeners

AbstractThe cure reaction of diglycidyl esters containing bicyclo[2.2.2]oct‐7‐ene units with phthalic annhydride, hexahydrophthalic anhydride, bis(4‐aminophenyl)methane, and bis(4‐aminophenyl)ethane as hardeners was studied by differential scanning calorimetry. The use of 4‐dimethylaminopyridine as a catalyst agent for the anhydride–epoxide reaction was also investigated. Depending on the curing agent, anhydride or amine, and the concentration of the catalyst, differences in activation energies were found, but negligible changes are observed between both anhydrides and the two primary amines. Thermal properties of the final product were unaltered by the hardener used. © 1995 John Wiley & Sons, Inc.

Synthesis of diglicydilesters with alicyclic imide structure and their thermal and tertiary amine catalyzed curing

AbstractThe synthesis of new diglycidylester compounds with bicyclo[2.2.2]oct‐7‐ene units was carried out from the previously synthesized diimide‐diacids and epichlorohydrin in excess using BTMA as catalyst. These compounds were characterized by spectroscopic techniques and have been cured either thermally or using 4‐dimethylaminopyridine as tertiary amine catalyst. The study of curing reaction was carried out through thermal analysis of the reaction by differential scanning calorimetry (DSC). The concentration of the tertiary amine affects the reaction mechanism of epoxide curing, but it does not influence the thermal properties of the final product. © 1995 John Wiley & Sons, Inc.

Investigation of polyimides containing naphthalene units. II. Model compounds synthesis

AbstractA series of model compounds from 4‐benzoyl‐1,8‐naphthalene anhydride and aromatic amines and diamines has been synthesized. The influence of the reaction conditions on the structure of the compounds obtained has been investigated to explain the high‐temperature polycondensation reaction mechanism. It was found that at high‐temperature polycondensation of 1,8‐naphthalene‐type anhydrides with aromatic amines, isoimides with cis and and trans structures are formed instead of amic acids. The only trans isoimides may isomerize to imide structure. © 1995 John Wiley & Sons, Inc.

Cyclic Carboxylic Imide Structures as Structure Elements of High Stability. Novel Developments in Perylene Dye Chemistry

Cyclic Carboxylic Imide Structures as Structure Elements of High Stability. Novel Developments in Perylene Dye Chemistry

Synthesis of poly(amide-imide)s by palladium-catalysed polycondensation of aromatic dibromides containing imide structure, aromatic diamines and carbon monoxide

A general method for the preparation of aromatic poly(amide-imide)s, which involves the palladium-catalysed polycondensation of aromatic dibromides containing imide structural units, aromatic diamines and carbon monoxide, has been developed. Polymerizations were carried out in N,N-dimethylacetamide (DMAc) in the presence of palladium catalyst, triphenylphosphine and 1,8-diazabicycIo[5,4,0]-7-undecene (DBU), and gave a series of poly(amide-imide)s with inherent viscosities up to 0.66 dl g-1 under mild conditions. The polymers were quite soluble in strong acids, dipolar aprotic solvents and pyridine. Thermogravimetry of the polymers showed excellent thermal stability, indicating that 10% weight losses of the polymers were observed in the range above 460C in air. The glass transition temperatures of the polymers ranged from 240 to 262C. These polymers also showed good tensile strengths and moduli.

Synthesis and Characterization of N-Phenylated Wholly Aromatic Non-Cyclic Polyimides from N,N′-Diphenylphthalimidoyl Chlorides and Phthalic Acids

A novel class of polyimides, N-phenylated wholly aromatic non-cyclic polyimides, was synthesized by the low-temperature solution and two-phase phase-transfer catalyzed polycondensations of new aromatic bis(imidoyl chloride)s, N,N′-diphenylisophthalimidoyl chloride and N,N′-diphenylterephthalimidoyl chloride, with aromatic dicarboxylic acids, isophthalic acid and terephthalic acid. The resulting polyimides were all white in color and had reduced viscosities of 0.11–0.14 dl g−1. Compared with the conventional polyimides having cyclic imide structures, these N-phenylated non-cyclic polyimides exhibited better solubility in various organic solvents, reduced crystallinity and lower glass transition temperatures and thermal stability. The reduced viscosity of a typical polyimide decreased rapidly upon UV light irradiation, indicating the occurrence of photodegradation. Before the polymer synthesis, the effects of reaction medium, organic and inorganic bases and phase-transfer catalyst were studied on the solution and two-phase reactions of N,N′-diphenylisophthalimidoyl chloride with benzoic acid.

Disposition Pharmacokinetics and Metabolism of Aniracetam in Animals

This review summarises what is currently known of the preclinical pharmacokinetics of the cognition enhancer, aniracetam (Ro 13-5057). This drug combines 2 moieties, an anisoyl and a 2-pyrrolidinone group, which form a substituted imide structure. The metabolism of the drug has been thoroughly examined by use of several radiolabelled forms. The compound is rapidly cleaved to produce 3 primary metabolites: anisic acid, N-anisoyl-γ-aminobutyric acid and 2-pyrrolidinone. The latter compound undergoes extensive additional metabolism. Most of a radiolabelled dose is recovered in the urine with a small fraction appearing in the faeces and as CO2 in expired air. The drug is totally metabolised, as the unchanged form is not recovered in excreted fluids. The parent compound is rapidly eliminated from the body and has a short half-life and large systemic clearance. Hepatic metabolism appears to account for most of the drug clearance; however, there may be contributions from the lung, vascular tissues and blood. One or more metabolites are lost more slowly than they are formed and one such compound appears to be succinimide. The gastrointestinal absorption of aniracetam is rapid and complete; however, only a very small fraction of the dose reaches the systemic circulation intact. The large apparent oral clearance is explained by presystemic elimination processes involving the liver, lung, and gastrointestinal tract and fluids. Aniracetam has a large apparent volume of distribution with only moderate binding to plasma proteins (approximately 66% bound). The drug traverses the placenta to produce measurable concentrations of intact drug in the fetus; however, most radioactivity found there is associated with metabolites. Aniracetam does not accumulate in the body with long term multiple administration but there is some accumulation of metabolites.

Aspartimide formation in the joining peptide sequence of porcine and mouse pro-opiomelanocortin.

The joining peptide (JP) portion of pro-opiomelanocortin extracted from mouse pituitary glands has previously been shown to exist in one major and several distinct minor forms (Bennett, H. P. J. (1986) Peptides 7, 614-622). We now confirm the heterogeneous nature of JP extracted from mouse neurointermediate pituitary glands and show that similar forms of JP are also to be found in extracts of porcine pituitary glands. Three forms of porcine JP (pJP-A, pJP-B, and pJP-C) were purified from whole porcine pituitary glands using reversed-phase high performance liquid chromatography methods. The three structural variants constitute approximately 10, 75, and 15%, respectively, of the total JP observed. Mass spectrometric analysis revealed that pJP-C was 18 mass units smaller than pJP-B, which is consistent with the formation of a succinimide structure at the aspartyl 16-glycine 17 peptide bond. Such symmetrical imide structures are known to hydrolyze at physiological pH to yield a mixture of the original alpha-aspartyl peptides and isomerized isoaspartyl peptides. We were able to show that pJP-A was the isomerized isoaspartyl form by demonstrating that pJP-A but not pJP-B was a substrate for the protein carboxyl methyltransferase enzyme (L-isoaspartyl/D-aspartyl protein methyltransferase; EC 2.1.1.77) purified from bovine erythrocytes. This cytosolic enzyme is known to preferentially methylate L-isoaspartyl residues within model substrates. Control experiments in which JP was incubated in the acidic medium used to extract the pituitary tissue showed that the isoforms of pJP are not artifacts of peptide purification. Furthermore, we have isolated the isoforms of pJP at levels which are 100 times greater than would be expected for a spontaneous reaction. We conclude that the formation of the aspartimide form of JP appears to be a facilitated process, possibly occurring as a result of conformation constraints dictated by the structure of pro-opiomelanocortin, or an as yet uncharacterized post-translational event.

Effects of aging on polyimide: A study of bulk and interface chemistry

AbstractWe are investigating the bulk and interfacial chemistry of polyimide (PI) exposed to heat and relative humidity (RH) stress (85°C/85% RH) over long periods to understand the long‐term reliability aspects of PI for microelectronic applications. The PI surface chemistry and the PI–Si interface chemistry was followed with electron spectroscopy for chemical analysis (ESCA). For exposure times greater than 550 h, the PI surface exhibits significant changes in emission structure and atomic concentration. The PI–Si interface indicates little change in the PI chemistry when compared to control samples. The water‐contact angle at the PI surface shows no statistically significant change as a function of exposure time. Bulk and surface chemistry were followed with Fourier transform infrared spectroscopy (FTIR) in a grazing incidence reflection configuration. There were measurable differences in FTIR spectra between aged and control samples only for the case of very thin PI layers. These results suggest that for exposure times of less than 1100 h, chemical changes in PI occur primarily at the PI–air interface for samples 1 μm thick and greater. These changes represent a possible rearrangement of the imide structure and may be a form of deimidization of the polymer, but the final state is not polyamic acid. The PI surface chemistry changes observed with ESCA are reversible upon reheating to the cure temperature.

A novel synthetic route to rigid‐rod polyimides

AbstractA new synthetic approach to soluble, rigid‐rod, aromatic polymides is described. The polycondensation is done by a Pd‐catalyzed aryl‐aryl coupling of N,N′‐bis(4‐bromo‐2,5‐didodecyl‐phenyl)‐1,2:4,5‐pyromellitic diimide (2) and 2,5‐didodecyl‐1,4‐benzenediboronic acid (3). Here, the imide structure is already preformed in monomer 2. A structurally identical polymer is synthesized by the classical procedure condensing 1,2:4,5‐pyromellitic dianhydride (PMDA) (4) and 4,4″‐diamino‐2,5,2′,5′,2″,5″‐hexadodecyl‐p‐terphenyl (5). Both polymers are characterized in detail by 1H and 13C NMR spectroscopy, membrane osmometry and size exclusion chromatography. The average degree of polycondensation is of the order of 15. The thermal behaviour of the polymers is studied by differential scanning calorimetry and thermogravimetrical analysis.

Cyclotrisulfimide - Synthesis and Properties

Abstract Cyclotrisulfimide (1,3,5,2,4,6- trithiatriazine-1,1,3,3,5,5-hexoxide) (1) has been synthesized successfully from persilylated sulfanuric acid (2) and hydrogen chloride in dichloromethane and has been isolated in pure form. Correlations of infrared and 15N-NMR spectra support assignment of the imide structure of (1). Ring cleavage appears to characterize reactions of (1) with solvolytic reagents. Thermal decomposition of (1) has been studied by TG accompanied by TLC methods. Reaction with diazomethane in dioxane yields the N,N,N-trimethyl derivative (3). Hitherto unknown (2) has been prepared from the trisilver salt of (1) using uimethylchlorosilane. The compound (2) has been characterized by IR, 15N-NMR and by X-ray crystallography. In the structure the S3N3 ring adopts a flattened chair conformation with the silyl groups being axial.

Acetylene-terminated polyimide cure studies using carbon-13 magic-angle spinning NMR on isotopically labeled samples

The cure mechanisms of an acetylene-terminated polyisoimide [CO-Ph(C 2 O 2 )=NPhOPhOPhN=(C 2 O 2 )Ph] n were studied. The NMR results showed that the carbonyl function remained unchanged in the cured product. The isoimide/imide carboxyl carbons underwent an isomerization reaction to produce the expected imide structure. The solid-state ethynyl cure products were found to contain aromatic structures, condensed polycyclic aromatic structures, backbone addition and bridge structures.