Polymer Science, Series B最新文献

New hydrogels based on arabinogalactan polyaldehyde and glutaric and tartaric dihydrazides have been synthesized. Arabinogalactan polyaldehyde was synthesized via periodate oxidation and characterized by NMR, IR, and UV spectroscopy. The synthesis of hydrogels is based on a click reaction between the aldehyde groups of oxidized arabinogalactan and the amino groups of crosslinking agents, yielding Schiff bases in crosslinks. The effect of hydroxyl groups of the crosslinking agent on the properties of the resulting hydrogels was investigated. It was found that the hydrogels formed using glutaric dihydrazide, which does not contain hydroxyl groups, exhibit a lower elastic response in the frequency rheology test and lower shear modulus compared to hydrogels crosslinked with tartaric dihydrazide. The use of hydroxyl-containing tartaric dihydrazide as a crosslinking agent allows the synthesis of hydrogels with good mechanical properties and high hydrolytic stability in both neutral and acidic media. A distinctive feature of the hydrogels obtained is their resistance to swelling at various pH values, which decreases slightly after hydrogels treatment with sodium borohydride. The effect of arabinogalactan oxidation conditions on the properties of the hydrogels is also discussed.

A novel catalyst system containing a complex of Ti(IV) with a bidentate diolate ligand and a binary Al(C₂H₅)₂Cl/Mg(C₄H₉)₂ activator at a molar [Al]/[Mg] ratio of ~3 affords the synthesis of high-molecular weight polyethylene and ethylene copolymers with 1-hexene, 1-octene and 1-decene. Kinetic analysis shows that the catalyst contains two families of active centers, unstable and stable. The unstable centers, which dominate at the early stages of the polymerization reactions, produce polymers of high molecular weight and narrow molecular weight distribution (M_w/M_n ~ 2.5), similarly to alkene polymers prepared with several soluble metallocene and post-metallocene catalysts. The stable active centers produce polymers of lower molecular weight and broad molecular weight distribution, which is more typical for polymers produced with heterogeneous catalysts.

Two series of novel sulfonated poly(arylene ether phosphine oxide)s were synthesized by incorporating cheap bisphenol A or bisphenol AP into the backbone via direct polycondensation. Both sulfonated poly(arylene ether phosphine oxide)s could be cast into uniform and ductile membranes. Their properties as proton exchange membranes were investigated and compared in detail. As a result, the sulfonated poly(arylene ether phosphine oxide)s containing bisphenol AP units show better properties than polymer containing bisphenol A units with similar ion exchange capacity (IEC). For example, the former membrane shows a XY swelling ratio of 9.8%, a Z swelling ratio of 9.5%, a proton conductivity of 0.084 S/cm and 100% residual weight after immersing in Fentons’ reagent for 1 h at 80°C. Therefore, it is a promising proton exchange membrane for fuel cell due to cheap and high performance.

The first synthesis of polyetherimides (PEIs) of a copolymer structure based on bisphenol-A 4,4'‑diphthalic anhydride and methylenedianiline, containing 10 to 100 mol % of rigid-chain fragments of benzophenone (BPDA) and pyromellitic (PMDA) dianhydrides, is described. The resulting polymers were analyzed using IR spectrometry, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and melt flow index measurements. Quantitative characteristics of the heat-resistance and processability indicators of synthesized PEIs depending on the content of rigid-chain fragments have been determined. Results show that increasing the content of BPDA and PMDA units in the PEI structure enhances the heat resistance and thermal stability of the polymers, although the melt flow index decreases. The explanation of the observed effect based on the growth of intermolecular interaction and the formation of a crystalline phase is given. Optimal ratios of precursor dianhydrides were identified to achieve the best balance of heat resistance and processability. The resulting PEIs of optimal structure have glass transition and thermal destruction temperatures up to 25–40°C higher in comparison with unmodified PEI whilst retaining the ability to be processed through the melt. The obtained results open up broad application prospects of the developed co-PEIs as highly heat-resistant engineering thermoplastic materials.

The paper describes the synthesis of pectin-based hydrogels with different contents of methoxy groups. The pectin crosslinking has been carried out using acylhydrazone groups, the dicarboxylic acid dihydrazides being used as crosslinkers in the absence of any catalyst. It has been established that covalently crosslinked hydrogels are formed from highly methoxylated pectin even at low concentrations of the crosslinkers, whereas the formation of covalently crosslinked hydrogel occurs only at a high concentration of the cross-linker for low-methoxylated pectin. Rheological properties and network structure parameters of the pectin hydrogels as functions of the content of methoxy groups and the cross-linkers have been comprehensively studied. It has been shown that the shear modulus of the hydrogels increases slightly but regularly in the number of malonic–succinic–glutaric–adipic dihydrazide series of the cross–linkers and significantly depends on their concentration. It has been found that thermal stability of the pectin hydrogels increases with an increase in the content of the acylhydrazone bonds.

We have successfully developed a superhydrophobic and superoleophilic cellulose paper by in situ formation of polyhedral oligomeric silsesquioxane (POSS) blocks on its surface. These POSS blocks endow the cellulose paper with an optimal micro-nano structure and hydrophobic composition, resulting in superhydrophobicity and enhanced abrasion resistance. The modified cellulose paper was characterized using scanning electron microscopy, energy dispersion spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis to confirm the structures. The oil-water separation performance of the as-prepared paper was validated through preferential adsorption and gravity-driven separation processes, demonstrating high separation efficiency and throughput for various oil/water mixtures. This innovative approach provides a promising solution for large-scale oil spill accidents while offering excellent reusability and stability.

The present paper describes the formation of microplastics from foamed polystyrene as a result of exposure to insects, namely the larvae of the beetle Zophobas morio in real-life conditions. Larvae were cultured with foamed polystyrene in the absence of food and in control groups with normal nutrition. Most larvae survived and successfully developed into pupae. The effect of larvae on polystyrene is manifested by its mechanical destruction when larvae build tunnels in the volume of polystyrene material, resulting in the formation of a finely dispersed fraction of polystyrene (i.e., microplastics). FTIR, Raman, and NMR spectrometry methods revealed no significant differences in the original polystyrene and polystyrene crushed by larvae; also, according to the GPC data, no significant change in the molecular weight of polystyrene was detected as a result of contact with Z. morio larvae and passage through their gastrointestinal tract. The data obtained confirm that the main result of larvae impact on polystyrene foam is its crushing with formation of microplastic without chemical modification and change of molecular weight.

The effect of ultraviolet radiation on the physico-mechanical properties of fibrous composite materials modified with polysulfone has been studied. In most cases, ultraviolet radiation has virtually no effect on the properties of epoxy fiberglass. Nevertheless, the specific fracture toughness of the winding composite modified by 20 wt % of polysulfone has increased (by 45% or up to 1.9 kJ/m² after 5 days of irradiation). In other cases, the change in the properties (compressive and shear strength) of the composites has not exceeded 10%. In addition, in all the conducted experiments concerning the physico-mechanical properties, the addition of polysulfone has led to an increase in the characteristics of fiberglass (crack resistance, shear and compression strength).