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

Abstract

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