Kinetics of paramagnetic centers decrease at ageing of chemically carbonized derivatives of poly vinylidene fluoride

Relevance of the work. One of the future problems facing modern science is the synthesis and study of the properties of low-dimensional and nanoscale materials based on carbon. Chemical dehydrofluorination of poly vinylidene fluoride (PVDF) allows generating a carbon enriched layer on its surface. Chains of the original polymer may be a promising precursor for synthesis of quasi-1D (carbynoid) structures. Cleavage of fluorine and hydrogen atoms from a carbon skeleton results in formation of unpaired electrons, which contribute in electron spin resonance (ESR) absorption. Deactivation of the formed paramagnetic centers (PMC) can lead to formation of extensive fragments consisted of double and triple carbon-carbon bonds. Besides, one cannot exclude the possibility of other routes of paramagnetic centers deactivation. Studying the kinetics of paramagnetic centers deactivation in chemically dehydrofluorinated poly vinylidene fluoride may give the important information on carbynoid carbon synthesis. Theoretical calculations predict semiconducting type of conductivity for carbynoid carbon, which is of interest for its application in micro- and nanoelectronics. The key point for the further practical usage of a new carbon material is a stability of its physical and chemical properties during long-term storage. The aim of the research is to study in details the deactivation kinetics of paramagnetic centers at long-term storage of chemically dehydrofluorinated poly vinylidene fluoride derivatives; to reveal the atmospheric air effect on paramagnetic centers deactivation. The received data may give ideas on the mechanism of paramagnetic centers deactivation. Research method: ESR spectroscopy. Results. The authors have carried out the long-term measurements of the kinetics of ESR absorption reduction of synthesized samples, including those with limited access to air and low pressure. At least four types of paramagnetic centers, differing in deactivation rates, were revealed. The kinetics of deactivation of paramagnetic centers can be described by a set of first-order reactions. It is found that the fastest reactions occur with the atmospheric air

Kinetics of paramagnetic centers decrease at ageing of chemically carbonized derivatives of poly vinylidene fluoride

Relevance of the work. One of the future problems facing modern science is the synthesis and study of the properties of low-dimensional and nanoscale materials based on carbon. Chemical dehydrofluorination of poly vinylidene fluoride (PVDF) allows generating a carbon enriched layer on its surface. Chains of the original polymer may be a promising precursor for synthesis of quasi-1D (carbynoid) structures. Cleavage of fluorine and hydrogen atoms from a carbon skeleton results in formation of unpaired electrons, which contribute in electron spin resonance (ESR) absorption. Deactivation of the formed paramagnetic centers (PMC) can lead to formation of extensive fragments consisted of double and triple carbon-carbon bonds. Besides, one cannot exclude the possibility of other routes of paramagnetic centers deactivation. Studying the kinetics of paramagnetic centers deactivation in chemically dehydrofluorinated poly vinylidene fluoride may give the important information on carbynoid carbon synthesis. Theoretical calculations predict semiconducting type of conductivity for carbynoid carbon, which is of interest for its application in micro- and nanoelectronics. The key point for the further practical usage of a new carbon material is a stability of its physical and chemical properties during long-term storage. The aim of the research is to study in details the deactivation kinetics of paramagnetic centers at long-term storage of chemically dehydrofluorinated poly vinylidene fluoride derivatives; to reveal the atmospheric air effect on paramagnetic centers deactivation. The received data may give ideas on the mechanism of paramagnetic centers deactivation. Research method: ESR spectroscopy. Results. The authors have carried out the long-term measurements of the kinetics of ESR absorption reduction of synthesized samples, including those with limited access to air and low pressure. At least four types of paramagnetic centers, differing in deactivation rates, were revealed. The kinetics of deactivation of paramagnetic centers can be described by a set of first-order reactions. It is found that the fastest reactions occur with the atmospheric air

Kinetics of paramagnetic centers decrease at ageing of chemically carbonized derivatives of poly vinylidene fluoride

Актуальность работы. Одной из перспективных задач, стоящих перед современной наукой, является синтез и исследования свойств низкоразмерных и наноразмерных материалов на основе углерода. Химическое дегидрофторирование поливинилиденфторида позволяет создать на его поверхности обогащённый углеродом слой. Цепи исходного полимера могут оказаться перспективным прекурсором для синтеза квазиодномерных (карбиноидных) структур. В результате отрыва от углеродного скелета атомов фтора и водорода происходит образование неспаренных электронов углерода, которые дают вклад в ЭПР-поглощение. Дезактивация образовавшихся парамагнитных центров может приводить к образованию протяженных фрагментов сопряженных двойных и тройных углерод-углеродных связей. Также нельзя исключить и другие механизмы дезактивации парамагнитных центров. Изучение кинетики разрушения парамагнитных центров в химически дегидрофторированном поливинилиденфториде несет важную информацию о процессе формирования карбиноподобного углерода. Теоретические расчеты предсказывают полупроводниковый тип проводимости карбиноподобного углерода, что представляет интерес для его применения в микро- и наноэлектронике. Ключевым моментом для дальнейшего практического использования является изучение стабильности физико-химических свойств нового углеродного материала при его долговременном хранении. Цель работы: подробно изучить кинетику дезактивации парамагнитных центров при долговременном хранении химически дегидрофторированных производных поливинилиденфторида; выяснить влияние атмосферного воздуха на процесс дезактивации парамагнитных центров; на основе полученных данных выдвинуть предположения о механизмах дезактивации. Метод исследования: ЭПР-спектроскопия. Результаты: Проведены долговременные измерения кинетики уменьшения ЭПР-поглощения синтезированных образцов, в том числе, в условиях ограниченного доступа воздуха и пониженного давления. Выявлено по меньшей мере четыре типа парамагнитных центров, отличающихся скоростями дезактивации. Кинетика процессов исчезновения парамагнитных центров может быть описана совокупностью реакций первого порядка. Установлено, что самые быстрые реакции происходят с участием атмосферного воздуха.Relevance of the work. One of the future problems facing modern science is the synthesis and study of the properties of low-dimensional and nanoscale materials based on carbon. Chemical dehydrofluorination of poly vinylidene fluoride (PVDF) allows generating a carbon enriched layer on its surface. Chains of the original polymer may be a promising precursor for synthesis of quasi-1D (carbynoid) structures. Cleavage of fluorine and hydrogen atoms from a carbon skeleton results in formation of unpaired electrons, which contribute in electron spin resonance (ESR) absorption. Deactivation of the formed paramagnetic centers (PMC) can lead to formation of extensive fragments consisted of double and triple carbon-carbon bonds. Besides, one cannot exclude the possibility of other routes of paramagnetic centers deactivation. Studying the kinetics of paramagnetic centers deactivation in chemically dehydrofluorinated poly vinylidene fluoride may give the important information on carbynoid carbon synthesis. Theoretical calculations predict semiconducting type of conductivity for carbynoid carbon, which is of interest for its application in micro- and nanoelectronics. The key point for the further practical usage of a new carbon material is a stability of its physical and chemical properties during long-term storage. The aim of the research is to study in details the deactivation kinetics of paramagnetic centers at long-term storage of chemically dehydrofluorinated poly vinylidene fluoride derivatives; to reveal the atmospheric air effect on paramagnetic centers deactivation. The received data may give ideas on the mechanism of paramagnetic centers deactivation. Research method: ESR spectroscopy. Results. The authors have carried out the long-term measurements of the kinetics of ESR absorption reduction of synthesized samples, including those with limited access to air and low pressure. At least four types of paramagnetic centers, differing in deactivation rates, were revealed. The kinetics of deactivation of paramagnetic centers can be described by a set of first-order reactions. It is found that the fastest reactions occur with the atmospheric air