Polymer Science, Series B最新文献

Mathematical modeling of the kinetics of peroxide vulcanization of rubbers based on butadiene–nitrile rubbers and their deformation–strength properties has been carried out. The modeling results are compared with the experimental data obtained for carbon black-filled compositions based on NBRS-40AMN rubber, including the vulcanizing agent 1,4-di(tert-butylperoxyisopropyl)benzene in different dosages. The mathematical model of the vulcanization kinetics of the compositions relies on the analysis of the formal kinetic scheme of radical reactions occurring during peroxide vulcanization in the presence of air oxygen. Using this model the influence of oxygen on the ratio of carbon–carbon and ether–ether crosslinks in the formed vulcanization network is analyzed. To describe the deformation curves of peroxide vulcanizates with different content of the vulcanizing agent, a model based on the series decomposition of the network strain energy by invariants of the left Cauchy–Green strain tensor and including the linear viscoelasticity equation is proposed. The vulcanizate breakdown process is characterized by a kinetic equation in which a network deformation model is used which allows an adequate description of the deformation curves of crosslinked elastomers up to failure. By analyzing the dependences of the model parameters on the content of the vulcanizing agent, conclusions are made about changes in the structure of the vulcanization network with increasing degree of crosslinking.

The degradation of stone cultural relics due to environmental factors, such as freeze-thaw, acid rain, and UV radiation, has necessitated the development of advanced protective coatings. In this study, fluorinated poly(methyl methacrylate-butyl acrylate) modified by vinyl triethoxysilane coating was synthesized via a one-pot method to enhance the durability and protective performance of coatings. The structure, thermal stability, and microstructure of the synthesized polymer were characterized using FTIR, XRD, TG, and SEM. The aging resistance of the coating formed was systematically evaluated under simulated freeze-thaw, acid, and UV aging conditions. Key properties, including hydrophobicity, chromaticity difference (ΔE), transparency, and mass loss rate, were analyzed before and after aging. Among the aging factors, UV exposure exhibited the most pronounced impact on these properties. However, polymer coatings with 18.5 mmol vinyl triethoxysilane demonstrated superior resistance to UV-induced degradation, maintaining a contact angle of 104.55°, the stability change of ΔE is 0.73, and acceptable transparency and mass loss rates after aging.

Acrylate emulsions were prepared through atom transfer radical polymerization (ARGET-ATRP) with methyl methacrylate (MMA), ethyl acrylate (EA) and butyl acrylate (BA) as monomers using electron transfer-activated regenerative catalysts, with benzyl bromide (BBB) and ethyl 2-bromoisobutyrate (EBIB) as a complex initiation system and copper bromide and bipyridine as a catalytic system. The effects of the temperature, the compound initiator ratio, the compound emulsifier ratio, the ligand type and the content on the polymerization dynamics were examined, and the polymer was characterized by infrared spectroscopy and 1H NMR. This study revealed that the monomer conversion rate and the apparent polymerization rate are positively correlated with the reaction temperature, and the apparent activation energy of the reaction was E_a = 57.63 KJ/mol. When benzyl bromide was used as the initiator alone, the initiation efficiency of the system was low. After EBIB was added, the initiation effect was greater for benzyl bromide : EBIB = 7 : 3, and the conversion rate and polymerization rate were positively correlated with the amount of reducing agent. The monomer conversion rate and apparent growth rate constant were the greatest when the mass ratio of the emulsifier sodium dodecyl sulfate and sodium dodecyl benzene sulfonate was 7 : 3. Different ligands affected the monomer conversion rate and apparent growth rate constant, and with increasing ligand content, the monomer conversion rate and apparent polymerization rate constant increased. According to the results of infrared spectroscopy and nuclear magnetic hydrogen spectroscopy, the compound initiator successfully triggered the polymerized monomer to generate the ternary copolymer.

Nonlinear amphiphilic thermoresponsive copolymers of N-isopropylacrylamide with triethylene glycol dimethacrylate containing amino or carboxyl end groups were synthesized by radical copolymerization in ethanol in the presence of cysteamine or 3-mercaptopropionic acid. Their molecular weights, polydispersity, and glass transition temperatures were determined. The behavior study of the copolymers in water showed that the cloud point depends on the concentration of the copolymers in solution, their composition, and nature of functional groups. The copolymers of N-isopropylacrylamide demonstrate low cytotoxicity against Vero and HeLa cells, which allows their use in biomedical applications.

A series of oligoisocyanurates of isophorone diisocyanate with different conversion of isocyanate groups have been synthesized in the presence of a 1,4-diazabicyclo[2.2.2]octane/propylene oxide catalytic system. The obtained samples have been characterized by IR and ¹³C NMR spectroscopy. It has been shown that the ratio of aliphatic and cycloaliphatic isocyanate groups in the oligoisocyanurates is close to that in the monomer. Investigation of kinetics of the urethane formation involving isophorone diisocyanate and its oligoisocyanurates with 2-hydroxyethyl methacrylate in the acetone medium has revealed that the presence of traces of the catalytic system in oligoisocyanurates significantly contributes to the urea formation reaction. In this regard, the synthesis of water-dispersive polyurethane acrylates based on isophorone diisocyanate oligoisocyanurates has been carried out in the medium of a hydrophobic solvent, methylene chloride. According to the analysis of the hydrodynamic parameters of the obtained aqueous dispersions, the size of the particles of the dispersed phase increases with an increase in the conversion of isocyanate groups in the oligoisocyanurates of isophorone diisocyanate. The observed regularities are apparently due to an increase in the content of the high-molecular fraction in the corresponding oligoisocyanurates.

To address the issue of poly(ethylene terephthalate) being highly hydrophobic and prone to static electricity due to friction, this study modifies PET through copolymerization with flexible long-chain monomers containing hydrophilic functional groups, creating a novel spinning-grade modified polyester with both hydrophilic and antistatic properties. Specifically, polyethylene glycol with a specific molecular weight (M_n = 4000) was used as a reactive hydrophilic and antistatic modification component, with a copolymerization content of 5~20%. Testing and characterization of the copolyester structure and properties showed that, compared to pure PET polyester, the introduction of hydrophilic ether bonds resulted in a significant hydrophilic modification effect, with the moisture absorption rate increasing from 0.11 to 1.12% and the surface water contact angle decreasing from 89.6° to 64.1°. Meanwhile, the volume resistivity of the copolyester decreased by 3–4 orders of magnitude compared to pure PET. This study improves the hydrophilic and antistatic properties of PET polyester through a low-cost modification method, providing essential reference for the development of functional polyesters and their fiber products.

In the present work, a comprehensive study is carried out to use amino acid mixed polyvinyl alcohol (PVA) based hybrid hydrogels as sensing material for detection of folic acid (FA). Thioglycolic acid (TGA) capped cadmium telluride (CdTe) nanostructures were used as dopant to enhance the efficiency and sensitivity of the PVA hydrogels. Three different types of hybrid hydrogels were synthesized using L-phenylalanine (PA), L-leucine (LEU) and L-tyrosine (TYR). Various chemical and physical characterizations were carried out to investigate the properties of TGA/CdTe nanostructures and PVA based hybrid hydrogels. A fluorescence quenching based detection technique was developed to detect the concentrations of FA. From the analysis of these six different hydrogels, it was observed that CdTe doped hybrid hydrogels show the best performance with sensitivity in the range of 0.229 µg/cm³ with limit of detection of 1.86 ng/cm³.

In this study, a new type of raspberry epoxy resin composite particle had been proposed. First, a reaction-induced phase separation method was used to solidify epoxy resin in PPG1000 to prepare homogeneous macromolecular epoxy resin microspheres (EMs). Then, a sol–gel method was used to hydrolyze tetraethoxysilane (TEOS) to prepare nanoparticles of silicon dioxide. In alkaline conditions, the two microspheres were compounded by isocyanate-terminated polyurethane oligomers (PU) to prepare raspberry-shaped EP-PU@SiO₂ composite particles. By adjusting the content of PU, the wettability of the composite particles (110°~156°) can be controlled. The surface morphology of the composite particles was observed via scanning electron microscopy (SEM). The test results indicate that, under the circumstance of the same mass ratio of EMs/SiO₂, when the content of PU is relatively low, there is essentially no SiO₂ attached to the surface of EMs; when the content of PU is relatively high, a raspberry-like structure is observed. Furthermore, the influence of different EMs/SiO₂ mass ratios on the wettability of the composite microspheres was examined. Although the degree of infiltration may differ slightly, it is not significant. This indicates that PU is the decisive factor in controlling the wettability of the EP-PU@SiO₂ composite particles. When the PU content is 400% and the mass ratio of EMs to SiO₂ is 1 : 1, the static water contact angle of the EP-PU@SiO₂ composite microspheres attains the maximum value of 156.2°.

The copolymers of L-lactide and ε-caprolactone are synthesized in the presence of tin(II) ethylhexanoate at 130°C for 72 h. The composition and structure of the products are determined by IR and ¹Н NMR spectroscopy, gel permeation chromatography, and elemental analysis. The molar ratio [monomer] : [initiator] = 4000 : 1 allowed the synthesis of the polymers with an number-average molecular weight of 47 000–66 000 g/mol with the polydispersity index not above 1.6. It was found that during transition from the glassy to highly elastic state, an increase in the content of ε-caprolactone units in the copolymer from 14 to 74 mol % leads to a decrease in the elastic modulus from 1379 to 65 MPa and a decrease in the maximum stress from 33 to 4 MPa. The copolymers containing 27 and 37 mol % of ε-caprolactone units possess plasticity and sufficient strength, which enables their use in medicine and the packaging industry.

Cardo block copolymers containing phenolphthalein-based aromatic polyester blocks and 10–30 wt % of polysulfone blocks have been obtained via low-temperature single-phase polycondensation from commercially available precursors. The obtained block copolymers have been characterized by the methods of IR spectroscopy, GPC, DSC, TGA, and DMA. The processibility of the obtained block copolymers was studied measuring the stability of the melt flow index over time at different temperatures. It has been shown that, depending on the content of the polysulfone blocks, the prepared block copolymers may consist of a single phase with only one variable glass transition temperature or be separated into two macrophases enriched in polysulfone or polyarylate blocks. From the practical point of view, the block copolymers containing 30% of the polysulfone blocks have exhibited good thermomechanical parameters up to 200°C and can be processed through the melt due to its relatively low-viscosity and high temperature stability. Time-temperature parameters of stability of the block copolymer melts have been determined and possible regimes of their processing via injection molding and extrusion have been elucidated.