Polymer Science, Series B最新文献

In this paper, acrylic acid based light-responsive molecularly imprinted polymers were synthesized for the molecular recognition of methylene blue with light regulation performance, enriching their application environments. The template-rebinding/-release studies of the molecularly imprinted polymers showed that their affinity of the adsorption recognition sites were successfully regulated by the cis-trans isomerization of the azo group in the polymers. Rebinding isotherms and rebinding kinetics show that the adsorption of methylene blue by imprinted materials conforms to the single-layer chemical adsorption and pseudo-second-order kinetic model.

A new monomer of the norbornene series, containing a substituent with 9,10-dihydroanthracene fragment and a bromine atom has been synthesized with a yield of 47% using the Diels–Alder reaction between norbornadiene-2,5 and 2-bromanthracene. Its metathesis and additive polymerizations have been investigated. The sorption properties of the two obtained polymers, as well as the gas transport properties of the metathesis polymer, have been investigated. It has been shown that the presence of polar bromine atom in the side chain does not affect the properties of the polynorbornenes with 9,10-dihydroanthracene moiety: like similar polymers without bromine atoms, the synthesized polymers have exhibited a moderate level of gas permeability, a large free volume, and a large specific surface area (540 m²/g in the case of the additive polymer). The polymer obtained by metathesis polymerization has shown slightly lower values of ideal gas separation selectivity of CO₂-containing gas pairs compared to the unsubstituted analog, but higher O₂/N₂ selectivity. Such bromine-containing polynorbornenes may be of potential interest as materials for the storage and separation of gases, the properties of which can be tuned using polymer-analogous transformations.

Silicon-modified urea–formaldehyde fibers (SiUFF) were prepared by adding different proportions of phenyltriethoxysilane to urea–formaldehyde resin, which were then subjected to dry-spinning and curing treatment. The SiUFF were characterized by Fourier infrared spectroscopy, micro-infrared analysis and ¹³C nuclear magnetic resonance analysis (¹³C NMR). It was found that the element silicon existed in the form of Si–O bond in the SiUFF, and the hydroxymethyl group cross-linked with the amino group to form methylene at the curing stage, while internal thermal conduction caused surface crosslinking density to exceed that of the fiber core. Optimal performance of SiUFF was achieved with 4 wt % Si-modifier addition, cured at 190°C for 30 min, exhibiting an elongation at break of 7.1%, a tensile strength reaching 389 MPa and a char yield of 30.01% at 1000°C, which represented significant improvements of 96, 92, and 14.2%, respectively compared to the unmodified urea–formaldehyde fiber.

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.