Polymer International最新文献

Crosslinked polymers are considered to be promising materials for supporting catalysts that are effectively applied in different reactions. However, the application of polymer-supported catalysts in high-temperature processes is limited by their temperature stability. Besides thermal degradation, temperature changes can cause the restructuring of the polymer network because of changes in the valence angles and bond lengths. Thus, the study of the influence of temperature on the structure of crosslinked styrene–divinylbenzene (StDVB) copolymers is an important task. In this work, for the first time, the temperature effect limitations on StDVB copolymers are studied and justified. The changes in the polymer structure tension as well as in the specific surface area are studied using molecular dynamics simulation in the temperature range 77–723 K. Near-cryogenic temperatures are not found to affect significantly the specific surface area. The heating of the polymer up to the temperature used for the reduction of catalysts (573 K) is shown to decrease the specific surface area by 11% because of an increase in the bond tension and valence angle deformation. Further increase in temperature leads to polymer decomposition. The results obtained can be considered for taking into account when applying polymer-supported catalysts. © 2024 Society of Chemical Industry.

This study focuses on developing a sustainable and biocompatible polycaprolactone (PCL)-based scaffold for bone tissue engineering through electrospinning, utilizing calcium carbonate (CaCO₃) from Pomacea canaliculata shells and keratin from human hair, known for stimulating bone regeneration. The isolated CaCO₃ has been identified to demonstrate two polymorphs, vaterite and calcite, as determined by X-ray diffraction. The isolation of keratin from human hair was confirmed through sodium dodecyl sulfate polyacrylamide gel electrophoresis and Fourier transform infrared spectroscopy analysis, revealing the presence of α-keratin structures around 45–50 kDa and β-keratin structures around 55–60 kDa. According to scanning electron microscope observations, the addition of keratin to PCL fibers reduced their diameter from 457 ± 345 to 371 ± 103 nm. Further addition of calcium carbonate led to a mean diameter of 258 ± 76 nm. The melting temperature of PCL fibers containing keratin and CaCO₃ was determined to be 76.17 °C via differential scanning calorimetry, while thermogravimetric analysis, conducted at temperatures up to 600 °C, revealed a remaining ash content of 9.59%. Calcium phosphate accumulation was observed to initiate on PCL fibers containing keratin and CaCO₃ following a 7-day exposure to simulated body fluid. The fibers exhibit cytocompatibility, showing no toxicity while supporting the growth and proliferation of Saos-2 osteosarcoma cells. The results suggest that the innovative incorporation of keratin and CaCO₃ into PCL nanofibers could serve as a bioactive matrix compared to pure PCL matrices, thereby offering enhanced potential for bone tissue engineering applications. © 2024 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A polyacrylonitrile (PAN) multi-filament bundle underwent a multi-step heat treatment following impregnation with a solution of ammonium bromide, phosphoric acid and urea (A-P-U). The multi-step thermal stabilization process was conducted in an air atmosphere at temperatures ranging from 200 to 245 °C for various stabilization times spanning from 10 to 70 min. Comprehensive analysis of physical and mechanical properties, infrared (IR) spectroscopy, X-ray diffraction (XRD) and thermal analysis (DSC and TGA) revealed the significant influence of stabilization time on the structure and properties of thermally stabilized PAN multi-filament bundle. The fiber thickness and linear density of the stabilized fibers decreased by approximately 29.5% and 10.6%, respectively, after 70 min of heat treatment. However, the fiber density value increased from 1.18 to 1.38 g cm⁻³ during the same stabilization time. Additionally, the carbon yield value obtained using TGA increased from 31% to 73% at 850 °C. The presence of A-P-U markedly reduced the time needed for the conversion of the PAN polymer into a cyclized structure through its nitrile groups, thereby accelerating the stabilization reactions. Furthermore, the IR spectra exhibited the appearance of CC bonds, signaling the creation of a crosslinked ladder-like structure. The XRD traces confirmed the decrease in crystallinity with increasing stabilization time, consistent with the findings from IR spectra. The findings showed that the A-P-U integrated system is notably successful and proficient in promoting the cyclization of nitrile groups, thereby decreasing the time needed to establish a thermally stable structure capable of withstanding elevated carbonization temperatures. © 2024 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Filler components play a crucial role as thermo-mechanical reinforcement to the epoxy-based solder mask, ensuring effective insulation and passivation. This study investigates the impact of different inorganic filler types (talc, silica (SiO₂), boron nitride (BN) and barium sulfate (BaSO₄)) and loadings (5 and 15 wt%) on the tensile and thermal properties of the epoxy composites. The composites were blended, cast and thermally cured. Of these composites, only 15 wt% SiO₂/epoxy composite exhibits notable increments in both tensile strength and modulus, surpassing unfilled epoxy by 11.65% and 31.9%, respectively. It also displays the highest elongation at break, supported by small particle size, high specific surface area and minimal void volume fraction. For thermal tests, the addition of all fillers increases the storage modulus in both glassy and rubbery regions, especially 15 wt% talc/epoxy composite with 30.09% increment at 25 °C. Additionally, all fillers raise the glass transition temperature (T_g), notably improving it by 9 °C in the 15 wt% BN/epoxy composite. Moreover, their inclusion generally enhances the onset decomposition temperature (T_onset) and reduces weight loss during decomposition. © 2024 Society of Chemical Industry.

Thermoplastic poly(vinyl alcohol) (PVA) with water-soluble behavior has received great attention. In this work, a thermoplastic PVA was prepared via solution radical polymerization of vinyl acetate, vinyl pivalate and sodium 2-acrylamido-2-methyl propane sulfonate (SAMPS). The effects of SAMPS content on the structure and properties of modified poly(vinyl alcohol) (MPVA) were investigated. On increasing the proportion of SAMPS, the characteristic band of –OH moved to a larger wavenumber. Compared to PVA, the melting temperature (T_m) of MPVA decreased from 223.1 to 161.5 °C at 0.03 mol of SAMPS, and the initial thermal decomposition temperature (T_d) of MPVA increased from 244.3 to 262.2 °C at 0.05 mol of SAMPS. The crystallinity of the resin reduced from 51.46% to 10.21%. The enlarged difference between T_d and T_m ensured the preparation of MPVA by thermal processing. The maximum tensile strength and elastic modulus of the obtained sheets were 137.56 and 2639.32 MPa, respectively. The introduction of SAMPS reduced the alcoholysis degree from 99.03% to 95.80%. The high alcoholysis degree of MPVA meant that it could be dissolved in water at 60 °C. This type of thermoplastic PVA shows a promising application on film and textiles that require water solubility. © 2024 Society of Chemical Industry.

Many cationic polymers with varied architectures either in backbones or in side chains have been used for gene delivery. However, these polymers yielding different DNA transfection efficiency cannot answer whether backbones or side chains have more influence on DNA delivery. In this research, polyurethanes (PUs) made from the reaction of l-lysine diisocyanate and 1,4-piperazinediethanol were synthesized. Together with poly(l-lysine) (PLL), these polymers were further modified to carry side chains by connecting to low-molecular-weight polyethylenimine (PEI) via imine linkages. The PEI was either linear (423 Da) or branched (600 Da) and grafted to the backbone representing two distinct shapes (i.e. a twig with needle-leaves or round-leaves). In addition, one PU derivative was synthesized to have shorter side chains (as PU-PEI S₄₂₃) than PU-PEI₄₂₃ by aminolysis reaction. These synthesized polymers were compared for their transfection potential as gene vectors into cells. Electrophoretic mobility, dynamic light scattering and zeta potential analyses of polymer/DNA complexes confirmed that, after grafting of PEI (PEI₄₂₃ or PEI₆₀₀), PLL-PEIs and PU-PEIs were able to self-assemble with plasmid DNA to form nano-scaled (ca 200 nm) and positively charged (ca +25 mV) complexes. These cationic polymers hardly showed any cytotoxicity on COS-7 cells. The outcome of fluorescence imaging and flow cytometry verified that the order of greater transfection efficiency is PLL-PEI₆₀₀ = PU-PEI₆₀₀ > PLL-PEI₄₂₃ = PU-PEI₄₂₃ > PEI_25K (commercial standard) = PU-PEI S₄₂₃ >> PLL > PEI₄₂₃ = PEI₆₀₀ (starting materials). These results reveal that the polymers with longer side chains or higher charge density have positive influence on transfection efficiency. Nevertheless, different polymer backbones may reflect their biodegradability and cytotoxicity, but their effect on transfection efficiency is less significant. © 2024 Society of Chemical Industry.

Resin is a widely used additive in rubber composites, which not only improves the processing properties of the composites but also enhances their mechanical properties, rolling resistance and wear resistance. However, there are specific differences in compatibility among resin, rubber and silica, which directly affect the performance of the composite materials. In this work, we first computed the glass transition temperature ($��T_g�$) of five resins in styrene−butadiene rubber (SBR) composites to prove the reliability of the computational method. Then, we explored the effects of different components and resin types on $��T_g�$ of SBR and found that the addition of silica can increase $��T_g�$ due to weak attractive interactions between silica and rubber molecular chains, which restrict the movement of the molecular chains. Furthermore, using solubility parameters, we analyzed the compatibility of rubber and five different resins and found that all five resins had good compatibility with rubber, especially C5/C9 copolymerized petroleum resin and hydrogenated resin. Finally, we revealed that there is a mutually attractive force between resin and silica. In summary, understanding the interactions among resins, silica and rubber is crucial for optimizing the performance of composite materials. © 2024 Society of Chemical Industry.

Recent advancements are notable in electrically conductive hydrogels emulating human skin functions. However, a significant challenge remains: crafting a single conductive gel that integrates self-healing, robust mechanical strength, and excellent electrical traits. Our innovation lies in a strong, lightweight, curable gel achieved through multiple coordination bonds between cellulose crystals and acid-treated multi-walled carbon nanotubes (MWCNTs) in a polymer network. Embedded MWCNTs act as dynamic bridges within a porous structure, giving exceptional mechanical performance. Reversible coordination interactions confer remarkable recovery and reliable mechanical and electrical self-healing. Additionally, these ionic gels function as adaptable stress sensors, detecting significant movements like finger and joint motions. This work introduces MWCNT-incorporated nanomaterials with good stretchability, high ion conductivity, remarkable self-healing nature, and good stress sensitivity. Such proteins hold promise for electronic sensors, wearable devices, and healthcare monitoring, unveiling a path to diverse applications. Our study addresses challenges and unlocks possibilities for materials that can adapt, withstand, and sense in innovative ways. © 2024 Society of Chemical Industry.