N. G. Stepanov

Complexes of acid amides with polar aprotic solvents

A study was made of the effects of organic carbonyl-containing compounds and inorganic acids on the character of complex formation of the solvent with polyacid amides, and in particular on the frequency of three-dimensional networks formed by hydrogen-bonds in solid polyacid amide films. It was found that the characteristics of the solid-phase cyclodehydration process can be varied within a wide range by means of active additives.ZusammenfassungDie Wirkung von organichen carbonyl-enthaltenden Verbindungen und anorganischen Säuren auf den Charakter der Komplexbildung von Lösungsmitteln mit Polysäureamiden wurde untersucht, inbesondere was die Häufigkeit von dreidimensionalen, durch Wasserstoffbindungen in den festen Polysäureamidfilmen zustande kommenden Vernetzungen betrifft. Es wurde festgestellt, daß die Kennwerte des Cyclodehydratisierungsprozesses in fester Phase innerhalb weiter Grenzen durch aktive Additive variiert werden können.РезюмеИсследовано влияние органических карбонилсодержащих соединений и неорганических кисл от на характер комплексообразован ия растворителя с пол иамидокислотами, полиамидокислотами, в частности, на частот у трехмерной сетки, об разованной водородными связами в твердых полиамидокислотных пленках. Показано, что с помощью активных добавок мож но изменять в широком диапазоне те мпературные характе ристики твердофазного проце сса циклодегидратац ии.

Odd-even effect and thermal stability in the series of vinyl polymers: Part 1. Poly-4-n-alkylstyrenes

Abstract Thermal transformations in the poly-4-n-alkylstyrene (PAS) series (from poly-4-methyl-styrene to poly-4-n-decylstyrene) have been studied with the aid of mass-spectrometric analysis, differential scanning calorimetry and thermogravimetric analysis. In the investigation of chemical properties of polymers, an odd-even effect of the thermal stability of poly-4-n-alkylstyrene, depending on the number of methylene groups in the alkyl substituent, was detected. It was shown that the odd-even effect is of electronic nature. The agreement between the thermal stability of polymers and the chemical shift on carbon atoms in the benzene ring and the alkyl substituent was established with the aid of 13C NMR spectroscopy. It was established that the character of the dependence of thermal stability on PAS structure varies with the conditions of analysis, in particular, with the heating rate and the medium, owing to change in the mechanisms for thermal degradation of the polymers.

Thermochemistry of Carbonization of Polypyromellitimide

The mechanisms of thermal degradation processes in polypromellitimide films were investigated by mass-spectrometric thermal analysis and high-resolution NMR spectroscopy in the solid state. Both the structures of the solid residues of pyrolysis products of the PM polyimide and the process of carbonization proper up to 1200° were studied. It was established that the breaking of the Car-O-Car bond in the diamine moiety is not the primary act of degradation of the molecular structure of the polymer, as might be expected on the basis of the value of the bond energy. The process of intermolecular crosslinking following polymer degradation under high-temperature conditions is completed by the formation of a complex nitrogen-containing heterocyclic structure.ZusammenfassungDer Mechanismus der in Polypyromellitfilmen ablaufenden thermischen Zersetzungsprozesse wurde durch massenspektrometrische thermische Analyse und hochauflösende Festkörper-NMR-Spektroskopie untersucht. Sowohl die Struktur des festen Rückstandes des Pyrolyseproduktes des PM-polyamids als auch der Prozeß der Verkokung bis 1200 °C wurden Untersucht. Es wurde festgestellt, daß das Aufbrechen der Bindung Car,-O-Car im Diaminteil nicht der primäre Schritt der Zersetzun der molekularen Struktur des Polymers ist, wie nach dem Wert der Bindungsenergie zu erwarten wäre. Der auf die Hochtemperatur-Polymerzersetzung folgende Prozeß der intermolekularen Vernetzung endet mit der Bildung einer komplexen stickstoffhaltigen heterozyklischen Struktur.РезюмеВ статье проводится а нализ данных методов масс-спектрометриче ского термического анализа (MTA) и спектроск опии ядерного магнит ного резонанса высокого р азрешения в твердом теле (ЯMP BPTT) так о с труктуре твердых ост атков продуктов пиролиза п олиимида ПМ, так и самом процесс е карбонизации вплот ь до температуры 1200 °C. В рабо те рассматриваются некоторые представл ения о механизме дест руктивных процессов в полиимид е. Показано, что разрыв с вязи Cap-Cap в диаминной компоненте не являет ся первичным актом разрушения структур ы хотя энергетически эта связь не прочнее, чем связи ими дного цикла, а в целом при глубоком пр огреве полипиромелл итимида последующий за дестр укцией полимера процесс межмолекуля рных сшивок завершае тся образованием сложно й азотосодержащей гетероциклической с труктуры.

Effect of hydrogen bonds on the solid phase cyclodehydration of polyamic acids

Abstract By X-ray structural analysis of the complexes of pyromllitdianilic acid with amide solvents it was found that the character of the system of hydrogen bonds and the structure of the solvates depend on the nature of the amide solvent. It was shown that in the case of polyamic acid solvates, the hydrogen bonds formed in the solid polyamic acid films can be studied by mass-spectrometric thermal analysis; from the obtained data, the mechanism may be determined of the function of additives catalyzing the solid phase cyclodehydration of polyamic acids.

Complexes of acid amides with aprotic polar solvents. IV: Complexes of poly(acid amides) with aprotic solvents

The process of solid-phase cyclodehydration of films cast from solutions of poly(acid amides) (PAA) in dimethylformamide, dimethylacetamide and N-methyl-2-pyrrolidone has been investigated by mass-spectrometric thermal analysis (MTA). It is shown that MTA is a structure-sensitive method making it possible to follow the appearance and changes in the character of ordered structures formed in PAA films. The authors relate these structures to the process of crystallization of complexes of PAA with aprotic polar solvents.ZusammenfassungDer Vorgang der Festphasen-Zyklodehydratation der Filme, die von Lösungen der Ply(Aminosäuren) (PAA) in Dimethylformamid, Dimethylazetamid und N-Methyl-2-Pyrrolidon ausgeschlagen wurden, wurde mit massspektrometrischer Thermoanalyse (MTA) untersucht. Es wurde erwiesen, dass die MTA eine struktursensitive Methode ist, die es ermöglicht, die Erscheinung und die Charakteränderungen der in den PAA-Filmen geformten, geordneten Strukturen nachzufolgen. Die Verfasser bringen diese Strukturen mit dem Kristallisationsprozess der Komplexe, bestehend aus PAA mit aprotischen, polaren Lösungsmitteln, in Zusammenhang.РезюмеМетодом масс-спектро метрического анализ а (MTA) исследован процесс т вердофазной циклодегидратации п ленок, отлитых из раст воров полиамидокислот в ди метилформамиде, диметилацетамиде и N-м етил-2-пирролидоне. Пок азано, что MTA явлпется структурно-чувствит ельным методом, позво ляющим следить за возникнов ением и изменением характера упорядоче нных структур, возник ающих в пленках полиамидоки слот, которые авторы связы вают с процессом крис таллизации комплексов полиамид окислот c апротонными полярны ми растворителями.

Odd-even effect and thermal stability in series of vinyl polymers: Part 2. Poly-n-alkyl acrylates

Abstract Thermal transformations in the series of poly-n-alkyl acrylates (PAA) have been studied by mass spectrometric thermal analysis method. Thermal degradation of PAA was shown to proceed via a six-membered transition state of the McLafferty rearrangement type. An odd-even effect in thermal stability of the PAA series depending on the number of methylene units in the alkyl side chain was observed. The electronic reasons for this effect were postulated on the basis of 13C NMR spectroscopy data.

Mass spectrometric thermal analysis of the cyclodehydration of polyamic acids

Abstract The gaseous products evolved in the solid phase cyclodehydration of films and fibre of poly-(4,4′-oxydiphenylene) pyromellitamic acid (PAA-PM) have been analyzed, using an MKh-1320 mass spectrometer. The character of the yield of residues of solvent and water during imidization of the polyamic acid was dependent on the time of ageing of the films. A change in the nature of solvents used for synthesis of the polyamic acid and the use of additives such as triphenylphosphate make it possible to alter temperature parameters of the cyclodehydration of polyamic acids.

Complexes of acid amides with polar aprotic solvents. II. Thermal analysis of the complexes of bis(N-phenyl)-pyromellitic acid amide with dimethylformamide, dimethylacetamide, N-methylpyrrolidone and dimethylsulfoxide

The synthesis of solid complexes of bis(N-phenyl)-pyromellitic acid amide (PMA) with aprotic solvents (dimethylformamide, dimethylacetamide,N-methylpyrrolidone and dimethylsulfoxide) and their thermal analysis (evolved gas analysis using mass spectroscopy, and thermogravimetry) is described. In all cases, the composition of the complexes was found to be 1PMA: 2 solvent. The activation energy of the decomposition process of the complexes was determined from TG data. The values found were between 40 and 80 kJ/mol.ZusammenfassungEs wird die Synthese der festen Komplexe von Bis(N-phenyl)-pyro-mellithsäureamid (PMA) mit aprotischen Lösungsmitteln (Dimethylformamid, Dimethylacetamid, N-Methylpyrrolidon und Dimethylsulfoxid) und deren thermische Analyse (massenspektrometrische Analyse der gebildeten Gase und Thermogravimetrie) beschreiben. In allen untersuchten Komplexen betrug das Zahlenverhältnis von PMA- zu Lösungsmittelmolekülen 2∶1. Die für die Zersetzung der Komplexe aufzubringenden Aktivierungsenergien wurden aus TG-Daten bestimmt. Die ermittelten Werte lagen zwischen 40 und 80 kJ·mol−1.РезюмеОписаны синтез и иссл едование методами масс-спектрометриче ского термического анализа (MTA) и термограв иметрического анали за (ТГ) твердых комплексо в бис-(N-фенил)-пиромеллит-амидокислоты (ПМК) с апротонными раствор ителями (диметилформ амид, диметилацетамид, N-мет илпирролидон, диметилсульфоксид). П оказано, что во всех исследова нных случаях комплек сы имеют состав [ПМК]1: [Sol]2. По данны м ТГ определены энерги и активации распада к омплексов, которые лежат в преде лах 40–80 кж/моль.

On the role of complexation with a solvent in the formation of supermolecular structures of polyamic acids

Abstract A study has been made of features of complexation of polyamic acids with aprotonic solvents. It is shown that a polyamic acid film is a solid solvocomplex with an aprotonic solvent that contains two solvent molecules per repeat-unit of the polymer. By changing the chemical nature of the solvent included in the solvocomplex one can control the formation of supermolecular structure in nonoriented polyamic acid films.

Electron cause of the evenness effect and its manifestation in the thermostability of a series of poly-4-n-alkylstyrenes☆

Using mass spectrometric thermal analysis and C NMR spectroscopy the authors have investigated a series of poly-4-n-alkylstyrenes (from methyl- to n-decyl-). In the distribution of electron density in the benzene ring the evenness effect shows up as a function of the number of carbon atoms in the alkyl fragment. This effect is also found in relation to the thermal stability of the polymers studied. Assumptions are advanced on the link between these phenomena.