Polyamido Acids Research Articles

Preparation and Properties of a Thermoplastic Partially Crystalline Polyimide in the Oriented State

Polyamido acids derived from 4,4′-bis(4-aminophenoxy)diphenyl (diamine) and 1,3-bis(3′,4-dicarboxyphenoxy)benzene dianhydride were synthesized in two amide solvents: dimethylformamide and N-methylpyrrolidone. Fibers with different extrusion ratios were obtained by the coagulation method. These fibers were converted to polyimide fibers by heat treatment. The influence of the solvent used in the polyamido acid synthesis and of the extrusion ratio on the structure and properties of polyimide fibers was examined. An increase in the extrusion ratio from 1 to 2 leads to an increase in the strength and elongation at break of the polyimide fibers.

Role of the intermolecular interaction in polymer fibre chemistry and technology

The existence of a specific intermolecular interaction of a hydrogen bond affects many polymerization processes and the occurrence of reactions in the chains of macromolecules. The features of the hydrogen bond in monomeric and oligomeric compounds are revealed. In production of aromatic polyamides, polyamido acids, polyimides, and the fibres based on them, the role of the hydrogen bond is reduced to the possibility of deliberate regulation of the chain rigidity.

New polymer systems based on alicyclic polyimides

Specific features of modification of some alicyclic polyimides with polyamido acids derived from aromatic tetracarboxylic acid dianhydrides were studied. The possibility of preparing new polymer systems with improved characteristics was demonstrated.

Effect of Fullerene on Cyclization of Polyamido Acids

The reaction of fullerene C60 with polyamido acid in the stage of its conversion into polyimide was studied by complex thermal analysis. The thermal and kinetic characteristics of this reaction and its probable mechanisms are discussed.

Kinetic Laws Governing the Synthesis of Adamantane-Containing Polyamido Acids and Polyimides

Kinetic Laws Governing the Synthesis of Adamantane-Containing Polyamido Acids and Polyimides

Investigation of the role of the pyrimidine ring in the main chain of polyamido acids and polyimides. 2. Characteristics of the thermocyclization of polypyromellitamido acids based on 2,5-bis(p-aminophenyl)pyrimidine and 4,4?-diaminoterphenyl

The thermocyclization of polypyromellitamido acids based on 2,5-bis(p-aminophenyl)pyrimidine and 4,4′-diaminoterphenyl was investigated by thermogravimetric and mass spectrometric analysis. Characteristics of the thermocyclization of pyrimidine-containing polyamido acids due to the presence of a basic nitrogencontaining ring in the main macrochain were revealed. The hypothesis advanced in Part 1, that the pyrimidine ring displaces solvent molecules bound to the polyamido acid, was confirmed. The hypothesis of the presence of shift packing in a pyrimidine-containing polyamido acid was confirmed by its greater kinetic homogeneity in comparison with the completely aromatic analog.

Investigation of the role of the pyrimidine ring in the main chain of polyamido acids and polyimides. 1. Supermolecular structure of polypyromellitimides based on 2,5-bis(p-aminophenyl)pyrimidine and its carbocyclic analog 4,4?-diaminoterphenyl

A detailed comparative study of polypyromellitamido acids and polyimides based on 2,5-bis(paminophenyl)pyrimidine and 4,4′-diaminoterphenyl was conducted to determine the role of the nitrogencontaining pyrimidine ring in the main chain of the polymers. A model of the layer packing of polyimide chains in crystalline regions was proposed based on the data from x-ray structural analysis and quantum chemical calculations. The existence of tilted packing caused by partial displacement of the solvent molecules bound to the pyrimidine ring of the neighboring macromolecule with higher basicity in pyrimidine-containing polymers was hypothesized.

Formation of polyimide from benzophenonetetracarboxylic acid diester complexes with different diamines. 4. Gas-chromatographic study of thermal cyclization of complexes

Thermal cyclization of H complexes is characterized by one rate constant which significantly distinguishes it from thermal cyclization of polyamido acids. The degree of completion of thermal cyclization of the H complex and its rate are determined by diffusion processes related to the structure of the H complex and mobility (softening) of the system during thermal cyclization.

Interaction of o-carboxyamide fragments of aromatic polyamido acids with halides in aprotonic amide solvents

The character of the change in the chemical shifts of the —NHCO— groups in PMR spectra with increase in the amount of salt in the solution in systems containing besides, o-amido acid fragments, o-carbomethoxyamide fragments and amide groups indicates the existance of intramolecular hydrogen bonds impeding to differing degrees the formation of an intermolecular bond with a halogen anion. The dependence of splitting of the signals of the amide groups of the various isomers in PMR spectra of the o-amido acids on the salt-to-—NHCO— ratio has a maximum. In some systems there is inversion of the signals. This confirms that the interaction of the o-carboxyamide fragments of the polyamido acids with halide ions in aprotonic amide solvents is not described by a single equilibrium equation. The changes in the chemical shifts of the protons nearest the amide and carboxyl groups, thanks to the magnetic anisotropy of the latter, reflect the conformational changes occurring on interaction of the o-carboxyamide fragment with a salt or a tertiary amine. The presumed structures of the complexes are presented.

ChemInform Abstract: Hydrohalic Acid Salts as Shift Reagents in the NMR Spectroscopy of Aromatic Polyamido Acids, Polyamido Esters, and Their Models.

ChemInformVolume 20, Issue 40 Physical Organic Chemistry ChemInform Abstract: Hydrohalic Acid Salts as Shift Reagents in the NMR Spectroscopy of Aromatic Polyamido Acids, Polyamido Esters, and Their Models. N. G. ANTONOV, N. G. ANTONOV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorV. M. DENISOV, V. M. DENISOV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorA. I. KOL'TSOV, A. I. KOL'TSOV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorA. A. SAFANT'EVSKII, A. A. SAFANT'EVSKII Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorA. B. SHUSTROV, A. B. SHUSTROV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this author N. G. ANTONOV, N. G. ANTONOV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorV. M. DENISOV, V. M. DENISOV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorA. I. KOL'TSOV, A. I. KOL'TSOV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorA. A. SAFANT'EVSKII, A. A. SAFANT'EVSKII Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this authorA. B. SHUSTROV, A. B. SHUSTROV Inst. vysokomol. soedin. AN SSSR, LeningradSearch for more papers by this author First published: October 3, 1989 https://doi.org/10.1002/chin.198940046AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue40October 3, 1989 RelatedInformation

Chromatographic study of synthesis and aging processes of polyamido acid under conditions of nonequivalency of functional groups

1. When initial monomers are added into a solution of polyamido acid, the degradation of poly[(4,4-oxydiphenylene)pyromellitamido] acid proceeds at an equal rate, irrespective of the nature of the monomer — the degrading agent; the interchain exchange reactions do not play an appreciable role in the aging process. 2. When solutions of polyamido acids obtained at the same lack of molar equivalency with respect to each of the monomers are mixed together, an increase in the length of the macromolecular chains is observed, as in the synthesis at an equimolar ratio of the monomers.

A kinetic study of the imidization of aromatic polyamido acids

An experimental procedure is given for obtaining the kinetic characteristics of the imidization of polyamido acids.

Structural features of moderately concentrated polymer solutions with different rigidity of the molecular chain

Scatter of non-polarized light has shown that the radius of the correlation of the fluctuations in polarizability ( a c) for solutions of flexible chain polymers (PS and PMMA) falls with rise in the concentration in a good solvent and remains constant in the τ system.In dilute solutions of these polymers the relation a c = R g √6 is fulfilled where R g is the radius of inertia of the isolated macromolecule. In moderately concentrated solutions of polyamido acids in DMFA micro anisotropic structures are found, which is linked with the raised rigidity of the elements of the molecular chain. The radii of the correlation of the fluctuation in orientation and polarizability decrease with fall in concentration, the last value on dilution tending to a value determined by the radius of inertia of the isolated macromolecule.

A mathematical description of the process of dehydrocyclization of polyamido acids

Modeling of two mechanisms of the imidization of polyamido acids has been carried out. The assumption has been made that the kinetic characteristics which are available in practice can be described by a set of parallel-sequential reactions, taking into account the different reactivity of structural conformations of the ortho carboxyamide groups.

Effect of degree of imidization of polyimede fibres on their sorptive power

The functional group content of a sorbent and its structure affect the sorption of water vapor to a large extent. As is well known [i], aromatic polyimides (PI) are prepared by dehydrocyclization of polyamido acids (PAA). Thereupon the polymers can have various degrees of cyclization (imidization), that is, different contents of active functional groups. Therefore it was of interest to examine, in the case of polyimides, the connection between sorption of water vapor and the degree of imidization, which can be determined with considerable accuracy by the method of IR spectroscopy [2, 3]. Moreover, obtaining the sorption characteristics of thermally resistant fibres has independent value; in the case of polyimides there are no such data in the literature. As objects of study we selected polyimide fibres obtained by thermal or chemical cyclization (Table i). The starting PAA fibres, arbitrarily called PM [4, 5] and VM[6], were prepared using pyromellitic dianhydride and diamino diphenyl oxide and 5(6)-aminophenyl-2-p-aminophenyl benzimidazole. Water vapor isotherms were determined on a vacuum sorption set-up using a McBain balance, at 25°C. The accuracy of the determination of the sorption value was ±0.05% by wt. and in determining pressure, ±5 Pa. Before the start of measurements, the samples were pumped out under vacuum at room temperature for 40 h, to constant weight, at a residual pressure of 0.01 Pa. The time to attain equilibrium at any point was 6-10 h. The degree of imidization, i, was determined by the procedure of [3].

Effect of inorganic acids on the cyclodehydration of polyamido acids

Effect of inorganic acids on the cyclodehydration of polyamido acids

The role of equilibrium state of the reaction of formation of polyamido acids in the process of their thermal cyclization in solution

The role of equilibrium state of the reaction of formation of polyamido acids in the process of their thermal cyclization in solution

Role of the intramolecular dissociation of amido-acid units during the solid-phase cyclization of aromatic polyamido acids

Role of the intramolecular dissociation of amido-acid units during the solid-phase cyclization of aromatic polyamido acids

Methods of investigation determining the degree of imidization of polyamidoacids

IR spectra of polyamido-acids (PAA) and corresponding polyamides of different chemical structures were analysed. It was shown that possibilities for quantitative determination of high degrees of imidization of PAA are the most favourable when using bands at 1660 cm −1 (amide I) and 1545 cm −1 (amide II). Using a machine programme for the separation of spectroscopic bands of PAA in the region of 1600–1800 cm −1 enables the degree of imidization of PAA (>0·9) to be established. The application of these methods to a number of polyimide samples shows that the polymer nature of materials is not a factor restricting imidization; defect-free structures may be obtained for some polymer samples, the same way as for a phthalanilic acid-N-phenyl-phthalamide model system.

Changes in the identity period along the fibre axis during the conversion of polyamido acids to polyimides

Identity periods d along the fibre axis obtained from various polyamido acids (PAA) and identity periods c′ along the axes of the same fibres after heat treatment and transition of PAA into polyimide (PI) were measured by X-ray methods. During the PAA → PI transition the identity period increases. This increase is 1–3% for PI without linked atoms in the chain or in PI with a linked atom in the dianhydride component. In PI with linked atoms in the diamine component an increase in the identity period reaches very high values (up to 10%). A difference in periods d and c′ may, apparently, serve as a further criterion of optimum techniques of making fibres from PI.