RESEARCH OF THERMAL AND THERMOMECHANICAL PROPERTIES OF COPOLYMERS BASED ON PYROMELLITE DIANHYDRIDE, 4,4'-DIAMINODIPHENYLOXIDE AND [2-(AMINOMETHYL)BICYCLO[2.2.1]HEPT-3-YL]ANILINES

The thermal and thermomechanical properties of copolyimides based on pyromellitic dianhydride, 4,4'-diaminodiphenyloxide and [2-(aminomethyl)bicyclo [2.2.1]hept-3-yl]anilines in an inert medium have been studied for the first time. It is shown that the introduction into the structure of aromatic polyimides up to 20 mol %. asymmetric vicinally substituted bicyclic diamines allows to obtain materials with increased hydrolytic stability in comparison with fully aromatic polyimides while maintaining a high level of thermomechanical characteristics.

Vibrational spectroscopy of thin film condensates of ethanol mixture with inert gase

It is known that by changing the concentration in an inert medium, it is possible to form clusters of various sizes of any substance by condensing them on a cold substrate from the gas phase. Traditionally, such systems are presented by molecular cryocrystals. This paper demonstrates the results of IR spectro­metric studies of cryovacuum condensates of ethanol mixture with nitrogen. The main task of this study is to explain the complex, most often, ambiguous behavior of thin films of ethanol cryovacuum conden­sates in the process of its co­condensation with nitrogen. For this purpose, vibrational spectroscopy of cryodeposited thin films of “ethanol in nitrogen” mixtures in various concentration ratios was performed. The objects of research are thin films of cryocondensates of ethanol mixture with inert gas (N2). The sam­ples were condensed at the temperature T = 16 K. The pressure of the gas phase of the mixture during cryocondensation was kept at P = 10­5 Torr. The range of ethanol concentrations in the mixtures varied from 3% to 90%. The spectral range of measurements was considered in 400­-4200 1/cm. It is assumed that the change in the concentration of ethanol in the mixture leads to the formation of various cluster compositions of ethanol molecules dissolved in an inert medium.

The use of differential calculation methods for the destruction of copolymers of polyethylene glycol fumarate with the acrylic acid

In this work, the thermal decomposition of copolymers based on polyethylene glycol fumarate with the acrylic acid using various ratios of initial monomers has been studied for the first time. The samples were studied in air and nitrogen. According to the thermograms analysis, it was found that the copolymer sample decomposition begins at higher temperatures for a copolymer with high content of polyester resin. The copolymer is vigorously oxidized by the oxygen when heated in air, and one can observe almost complete sample decomposition, whereas it decomposes with a residue of ~ 15% in an inert medium. The activation energies for copolymers with different compositions were estimated using the differential methods of Freeman-Carroll, Achar and Sharpe-Wentworth. The activation energy values found by the three methods demonstrated a good convergence. It was shown that, the activation energy values are higher (~ 200 kJ/mol in the inert medium, and ~ 95 kJ/mol in the oxygen atmosphere) for a copolymer with a lower composition of polyester resin, and the activation energy is ~180 and ~85 kJ/mol for a copolymer with a greater composition of p-EGF-AA. The copolymer is more thermostable in the nitrogen atmosphere according to the kinetic parameters. Additionally, there were determined the thermodynamic characteristics, such as the Gibbs energy (∆G) and the entropy (∆S). They also confirm the destruction process dependence on the components ratio in the synthesized copolymer.