A. V. Gribanov

Thermochemistry of lignin

Thermochemical reactions occurring in various stages of structural transformations of native lignin in its thermal treatment in a wide temperature range are considered and classified. Attention is given to the initial state of lignin in its primary isolation without heating. The terminology of lignin products, used in the literature, is put in order to a certain extent. The thermochemical reactions in which lignins are transformed in processing of raw wood materials and the structure of isolated lignins undergoes changes in the course of the target thermal treatment are differentiated. The applied aspect of the directed thermochemical synthesis of new lignin-based low- and high-molecular-mass compounds is discussed.

Composites of lignin and polyacrylonitrile as carbon precursors

Films of polyacrylonitrile and lignin cast from dimethylformamide were studied by dynamic thermal analysis in a self-generated atmosphere and in a vacuum. The occurrence of a thermochemical reaction of the components on heating was demonstrated. The optimal conditions of the reaction between polyacrylonitrile and lignin were determined.

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.

Sorption of vapors of aromatic compounds by cross-linked polymer particles containing luminophores: A spectroscopic study

Monodispersed core-shell particles 290–315 nm in diameter were prepared by seed emulsion copolymerization of styrene with divinylbenzene in the presence of luminophore-containing comonomers. The capability of the particles obtained to sorb toluene vapor was shown by solid-state 1H and 13C NMR spectroscopy.

Criteria of polymer carbonization

The possibility of using numerical criteria of polymer carbonization was considered based of experimental data on the kinetics of thermal degradation and cross-linking of various polymers. The main methodological approaches to determining the parameters of thermochemical carbonization reactions and evaluating the prospects for predicting the properties of carbon materials on the basis of the existing carbonization criteria are assessed.

Cocarbonization of polyacrylonitrile with lignin

The boundary and parameters of the thermochemical reaction of lignin and polyacrylonitrile were determined by dynamic and isothermal thermal analysis. The time, temperature, and concentration effects of formation of composites, allowing preparation of new carbonizates with enhanced heat resistance and noticeably higher carbon residue, were studied.

Role of Structural Characteristics of Aromatic Polyimides in Carbonization

The influence of the structural characteristics of polyimides belonging to four standard classification groups was analyzed. The main factors responsible for formation of ordered and/or turbostratic carbon structures in the course of carbonization were studied for the example of film and fibrous materials.

Thermochemical Transformations of Hydrolysis Lignin

Conclusions on the reactivity of lignin in thermal processes are made on the basis of published data and results of thermal analysis of lignin samples from certain hydrolysis enterprises.

Synthesis and spectral characteristics of silicon-containing poly(salicylidene azomethines) derived from aromatic di- and tetraamines

New silicon-containing poly(salicylidene azomethines) were prepared by polycondensation of di-or tetrasalicylidene derivatives of aromatic di- or tetraamines. The spectral data suggest the occurrence of noncovalent transannular donor-acceptor interaction N→Si providing “nonclassical” conjugation.

Cocarbonization of polymers as a new concept for synthesis of carbon composites

Foundations of cocarbonization of a series of carbon-chain and heterochain polymers in the solid phase and in solution were considered; the concept of this process was formulated. The temperature and kinetic parameters of the maximal thermal activity were determined. The possibilities of intermolecular interactions of compatible macromolecular compounds depending on the chemical structure of the initial components of composites and concentration and temperature-time parameters were studied.