The study demonstrates new opportunities for improving the prediction of gas transport properties of glassy polymers based on their chemical structure using the Database of the Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences. A generalized linear model has been developed to predict permeability coefficients for any gas-polymer system based on structural descriptors of the polymer and gas properties, such as tabulated effective kinetic diameters of gas molecules and effective Lennard–Jones potential parameters. This model significantly expands the dataset available for predictions and the application of modern machine learning methods. The feasibility of using small residual neural networks to enhance the accuracy of linear model predictions is shown, and training such neural networks does not require significant computational resources.
The polycondensation of norbornane-2,3,5,6-tetracarboxylic acid dianhydride with various diamines has been studied for the first time in order to synthesize new polyimides based on cycloaliphatic dianhydride. Norbornane-2,3,5,6-tetracarboxylic dianhydride (NBDA) has been synthesized from cis-5-norbornane-exo-2,3-dicarboxylic anhydride. The possibility of obtaining polyimides based on norbornane-2,3,5,6-tetracarboxylic dianhydride has been studied by carrying out synthesis under different conditions. Chloroform-soluble, film-forming polyimides based on norbornane-2,3,5,6-tetracarboxylic dianhydride have been obtained by one-step catalytic polycyclocondensation of norbornane-2,3,5,6-tetracarboxylic dianhydride with aromatic diamines in a benzoic acid melt. According to the second method, the polyimide based on norbornane-2,3,5,6-tetracarboxylic dianhydride has been produced using a two-step procedure: low-temperature polycondensation of silylated cycloaliphatic diamine (N,N′-bis(trimethylsilyl)isophoronediamine) in an amide solvent to form a soluble prepolymer with its subsequent imidization in the solid phase. The heat treatment conditions have been optimized for the prepolymer, allowing the production of a polymer with a composition corresponding to the target polyimide. The obtained polymers have been characterized by IR spectrometry, 1H NMR and solid-state 13C NMR spectroscopy, elemental analysis, and DSC and TGA techniques.
Metathesis oligomerization of norbornene in the presence of the first-generation Grubbs catalyst and ethylene used as a chain transfer agent yielded an oligomeric product, which was then hydrogenated over a palladium catalyst. After oligomerization and modification, the yield of the products was over 80 and 90
Crosslinking process kinetic parameters of mixtures based on low-molecular polyisoprene and MQ‑copolymers have been investigated by means of rotational rheometry. The rheological method allows tracking of the changes in the principal parameters of the system, such as viscosity, dynamic moduli, and the mechanical loss tangent during the entire chemical curing process. The evolution of viscous and viscoelastic properties of the system have been recorded under isothermal conditions as well as under conditions of continuous increase in temperature. Duration of the gelation in the systems has been determined under conditions of shear deformation via extrapolation of the dependence of reciprocal viscosity on time as well as from the crossover of the loss factor in a wide frequency range. Rheological properties of the filled systems about the gelation transition have revealed the power dependence of the dynamic moduli on the frequency, the critical parameter being equal to 0.54 at 100°C. The increase in the fraction of the inorganic component in the MQ-copolymers from 1 : 2 to 1 : 4 has led to an increase in the gelation time.
