Polymer Science, Series C最新文献

The influence of the composition of hybrid hydrogels based on macromonomeric unsaturated derivative of sodium alginate and diethylacrylamide synthesized by radical copolymerization with redox initiation on their structure and properties was studied. It was shown that the introduction and an increase in the content of alginate macromonomer lead to significant changes in the supramolecular structure of the hydrogels and cause a decrease in their swelling degrees. At the content of the alginate component in the hydrogels above 10 wt %, in addition to the network structure of the synthetic polymer, denser alginate networks are formed which determine an increase in the volume transition temperature. In vitro experiments on lidocaine release from the hybrid hydrogels carried out under different conditions demonstrate that the drug release rate depends on medium pH and temperature. The data obtained are of interest for designing stimuli-sensitive drug carriers.

The paper presents a method for obtaining hydrophilic CdSe/ZnS quantum dots by replacing the initial low-molecular organic stabilizing ligands on the surface of nanoparticles with polymeric ones. For this purpose, hydrophilic homo- and copolymer based on 2-dimethylaminoethyl methacrylate have been synthesized by the method of radical polymerization with reversible chain transfer (RAFT). Due to the presence of the terminal trithiocarbonate residue of the chain transfer agent (CTA) at the polymer chain, functional thio groups for the interaction with the surface of quantum dots have been obtained. For the possibility of further modification of hydrophilic quantum dots, polymer ligands have been additionally modified with tert-butyl acrylate units, which have been hydrolyzed into functional carboxyl groups. In this study, water-soluble CdSe/ZnS quantum dots have been obtained, coated with new polymer stabilizer ligands bearing several reactive carboxyl groups, which significantly expands the possibilities of application of hydrophilic nanoparticles.

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.

Atactic polycarbonate with the content of carbonate units above 99% has been synthesized by the copolymerization of racemic propylene oxide and carbon dioxide mediated by the salen complex of cobalt and bis(triphenylphosphine)iminium chloride. Its biodegradation under accelerated composting conditions has been studied. It has been shown that ammonia is the main abiotic degradant during the composting of poly(propylene carbonate). Polymer degradation proceeds at a low rate, is accompanied by a gradual decrease in molecular weight, and yields propylene glycol.

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.

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%, respectively. The structure of the oligomers was confirmed by ¹H and ¹³C NMR spectroscopy. Thermal and rheological properties of the obtained oligomer have been studied in detail.

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.

The influence of solvent vapor on the dielectric properties of films of polystyrene, poly(2-vinylpyridine), and poly(4-vinylpyridine) has been investigated. A procedure for the measurement of dielectric permittivity via the capacitor method under conditions of strong swelling of the films has been elaborated. It has been found that the swelling in chloroform vapor is the most prominent and leads to noticeable increase in the real part of the dielectric permittivity of the samples. This effect can be used to enhance the dielectric contrast between the domains of a block copolymer. It has been demonstrated that the observed decrease in the polymer glass transition temperature under condition of swelling can be approximated by the group contributions method.

The modification of addition poly(5-vinyl-2-norbornene) by the hydrogermylation reaction has been studied for the first time. Modification is carried out using triethylgermane as a model germane and an (NHC)Pt complex, which previously proved to be one of the most efficient catalysts of the hydrosilylation of such objects, as a catalyst. Optimization of the modification conditions of poly(5-vinyl-2-norbornene) allows the synthesis of high molecular weight soluble polymers containing 60‒65% of modified units.