Colloid and Polymer Science最新文献

A series of 2,2-diallyl-1,1,3,3-tetraethylguanidiniumchloride copolymers with N-vinylpyrrolidone (AGC-VP), vinylacetate (AGC-VA), and methacrylic acid (AGC-MAA) were obtained by free radical polymerization reaction. The guanidinium copolymers were loaded with silver nanoparticles, and there were investigated cytotoxic properties of the synthesized nanocomposites along with the features of interaction with model membranes (small anionic liposomes). The nanocomposites have a selective cytotoxic activity against cancer cell lines. Nano(AGC-VP) provokes a noticeable increase in cellular apoptosis in a dose-dependent manner and has great prospects as apoptosis inducer of A549 cells triggering only apoptotic cell death. All nanocomposites complexed with liposomes; herewith, the features of interaction with the lipid membrane were dependent on the composition of the copolymer in the nanocomposite. Nano(AGC-VA) had no destructive effect towards the liposomes and, in the case of Nano(AGC-MAA), negligible defect formation was observed. At the same time, Nano(AGC-VP) induced lateral segregation of lipids and formation of defects in the bilayer that resulted in irreversible interaction with liposomes. Detailed studies of the physicochemical aspects of liposome-to-nanocomposites interactions make it possible to understand the mechanism of action of composite materials, thereby bringing us closer to the possibility of practical application of the latter.

A comprehensive statistical analysis of the distributions of the adhesion strength (σ) developed during a long-term contact (up to 2 months) of two identical specimens of an amorphous entangled polymer at a very low temperature (T) of 24 °C with respect to the bulk glass transition temperature (T_g), below T_g by 80 °C, was carried out. For this purpose, two representative glassy polymers, polystyrene [PS; three PSs differing markedly in the number-average molecular weight (M_n) from 75 to 966 kg/mol] and poly(methyl methacrylate) (PMMA; M_n = 43.5 kg/mol), were selected. Keeping in contact the two specimens of PS or PMMA at T = 24 °C resulted in self-bonding at PS–PS and PMMA–PMMA interfaces. The as-self-bonded interfaces were shear fractured in tension to measure their σ values. The four σ distribution sets obtained for such a low T for the first time were examined using a number of common formal tests for normality and graphical statistical methods, including Weibull’s model. In general, the σ distributions for the PS with the highest M_n = 966 kg/mol were described more correctly than those for the other three polymers, regardless of the statistical methods applied. These results were compared with those obtained after self-bonding at a significantly higher T = T_g − 33 °C for the same polymers. The statistical parameters estimated at markedly different temperatures (T = T_g − 80 °C and T_g − 33 °C) were compared and discussed.

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Printable conductive composites show potential in wearable electronic, capacitor, stretchable sensors, and conductors. Incorporating metal nanoparticles in composites is a leading method to achieve high performance. In this study, we present a method for preparing silver flakes with ultra-smooth surfaces and excellent electron transfer properties by combining a waterborne acrylic resin template method with an intensive energy ultrasonic technique. By varying the ultrasonic treatment time from 20 to 80 min, the size distribution of the silver flakes was controlled, ranging from 15.7 to 5.04 μm. Scanning electron microscopy results indicate that the intensive energy ultrasonic treatment does not affect the surface morphology of the silver flakes. Additionally, the electron transport difficulties arising from internal defects in silver flakes prepared by traditional methods have been mitigated. The influence of size distribution and filler content on the electrical conductivity of silver conductive composites has been investigated. The study identified a correlation between the particle size distribution of flake silver powder and the volume resistivity of the conductive composite material, wherein a reduction in particle size distribution leads to a corresponding decrease in volume resistivity. Furthermore, an increase in the filler content of the composite material was found to result in a reduction in its volume resistivity. Using flake silver powder with a median particle size (d_0.5) of 5.38 μm as a representative sample, the volume resistivity was observed to increase from 8.50 × 10⁻⁵ Ω·cm to 8.63 × 10⁻³ Ω·cm as the silver content was decreased from 25 to 4 wt %. Concurrently, an examination of the conductive properties and the formation of the conductive network demonstrated alignment with the theoretical steady-state model.

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Silver flakes with ultra-smooth surface and excellent electron transfer property is prepared by combining vacuum-evaporated nanofilms method and intensive energy ultrasonic technique.

The exceptional heat transfer capabilities of hybrid base ferrofluids have attracted numerous researchers, prompting an increase in investigations into these working fluids. In various applications, hybrid base nanofluids have demonstrated superior heat transfer performance. However, further research is needed to expand their range of applications. To address this need, the current study aims to explore the flow of a hybrid base nanofluid (magnetite with ethylene glycol and water as the base fluid) on an exponential shrinking/stretching Riga plate with radiative heat flux. The Riga plate, an electromagnetic actuator, consists of a spanwise-aligned array of alternating electrodes attached to a flat surface and permanent magnets. This setup enables the examination of heat transfer with Hartmann number, thermal radiation, and nanoparticle volume fraction. The governing PDE systems are transformed into ODE systems using similarity transformations, and the developed model is solved numerically using the bvp4c technique in MATLAB software. A comprehensive convergence analysis and comparative investigation of numerical data are conducted to ensure the accuracy of the results. Finally, the effects of physical parameters on skin frictional force, Nusselt number, velocity field, and temperature field are investigated, and the results are presented graphically and discussed in detail. The numerical values for the skin frictional quantity variation along suction with different Hartmann quantity obtained. The critical values ({S}_{ci},i=1, 2), and (3) observed are (2.2396, 2.3795,) and (2.7714) corresponding to the values of (M) = (0, 0.02,) and (0.04), respectively. Research suggests that dual solutions are present within a specific spectrum of suction and stretching/shrinking parameters. Additionally, the stability analysis of these dual solutions indicates that the primary solution is stable.

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Porous melamine formaldehyde resin (PMF) was synthesized without using template in aqueous solution with a green preparation method. Conditions such as formaldehyde/melamine, concentration, curing temperature, and time on pore parameters of synthesized porous melamine formaldehyde resin were investigated. The chemical property and pore structure of porous melamine formaldehyde resin were characterized by infrared spectroscopy, SEM, and BET. The results showed that the samples synthesized in solvent water had a surface higher than 490 m²/g, pore diameter of about 12.0 nm, and pore volume of about 1.2 cm³/g. The surface area and pore structure of porous melamine formaldehyde resin could be adjusted by changing the prepolymer concentration. Due to the large pore diameter and volume, it also adsorbed a great amount of Congo Red (CR), indicating an excellent adsorbent for large molecules. This investigation reveals that the -NH₂ and pore structure have great effects on the adsorption capacity of Congo Red dye of the as-synthesized melamine formaldehyde resin samples.

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The porous melamine formaldehyde resin without using template was synthesized by a green preparation method. The pore structure of the melamine formaldehyde resin was formed by nanoparticles accumulation. The surface area and pore structure of porous melamine formaldehyde resin could be adjusted by changing the prepolymer concentration. The adsorption capability of the porous melamine formaldehyde resin for Congo Red was up 720 mg/g.

Thermoplastic polyester elastomer (TPEE) microcellular foam materials prepared using supercritical carbon dioxide (scCO₂) as a physical blowing agent suffer from poor dimensional stability, which significantly limits their applications across various fields. This study thoroughly investigates the prevalent issues of high shrinkage and low expansion ratio in the scCO₂ foaming process of TPEE. By introducing poly(lactic acid) (PLA), a rigid material with moderate compatibility, into TPEE through blend modification, we markedly improved the shrinkage behavior of foamed TPEE while enhancing its expansion ratio. The experiments successfully produced TPEE/PLA20 microcellular foams with a stable expansion ratio of 19 times. Compared to pure TPEE, the shrinkage rate decreased from 77.3 to 19.0%. Due to its moderate compatibility, PLA was uniformly dispersed within the TPEE matrix as a dispersed phase, which refined the cell structure through heterogeneous nucleation and reduced cell walls strain. Additionally, rigid PLA micro/nanoparticles acted as stress concentration points, promoting the formation of an open-cell structure by causing cell walls rupture, thereby accelerating gas diffusion. More importantly, high glass transition temperature (T_g) PLA nanoparticles are stretched and embedded in the cell walls during the foaming process, and the heterogeneous nucleation effect of PLA enhances the crystallinity of TPEE. These two factors together increase the rigidity of the cell walls. The synergistic effects of these factors enabled the TPEE/PLA microcellular foam materials to effectively resist shrinkage caused by the pressure differential between the inside and outside of the cells and molecular chain relaxation.

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In this study, a novel adsorbent—KOH-treated bentonite biochar composite (BRK) derived from natural bentonite and rice husk—was successfully synthesized to remove ammonium (NH₄⁺) from water. Adsorbent preparation involved pyrolysis at 400 °C followed by activation of biochar with KOH to produce BRK. Various techniques were applied to characterize the investigated adsorbent, including Fourier-transform infrared spectroscopy (FTIR), N₂ adsorption analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) integrated with energy-dispersive X-ray (EDX) spectroscopy. Batch experiments were conducted for elucidating the factors influencing the adsorption process, including pH, contact time, temperature, initial ammonium concentration, and the presence of co-existing cations in the solution. The results showed that the pH of the solution strongly affected BRK’s adsorption capacity for NH₄⁺ ions. Co-existing cations (Na⁺, K⁺, Ca²⁺, and Mg²⁺) significantly reduced the removal efficiency of NH₄⁺ ions. The Langmuir adsorption capacity of BRK for NH₄⁺ followed the order: 22.51 mg/g (10 °C) > 20.57 mg/g (30 °C) > 16.22 mg/g (50 °C). The negative standard enthalpy change (∆H°) obtained in thermodynamic study suggested that the adsorption process of NH₄⁺ was exothermic. The kinetic experiments demonstrated that adsorption equilibrium was achieved after 30 min of contact. Ion exchange was found to be the main adsorption mechanism for removing NH₄⁺ by BRK. This study proved that BRK is a low-cost and sustainable adsorbent derived from natural bentonite and rice husk and is advantageous for removing NH₄⁺ from water.

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Hot work can make oil pipeline maintenance more efficient but is dangerous. Traditional chemical hydrogels can plug oil pipelines to ensure the safety of hot work, but they cannot be completely removed afterward. Herein, we prepared a gelatin-reinforced hydrogel with thermal reversibility, which can be easily removed by injecting hot water. The hydrogel was prepared by the hydrogen bonds of the copolymer of N-acryloyl glycinamide (NAGA) and acrylamide (AM) as well as the interaction of the gelatin interpenetrating network. It was found that the hydrogen bonding interaction between the NAGA motif is the main driving force for the formation of hydrogels. The strength of the hydrogel is increased by 10 times after adding gelatin equivalent to the polymer. The thixotropic recovery properties test indicated that the hydrogel posed tunable mechanical and self-recovery properties, which contributed to the excellent plugging ability and injectability of hydrogels. Besides, the hydrogels exhibit favorable thermo-reversible gel-sol transition behavior, driven by the reversible disruption of hydrogen bonding interactions in response to temperature changes. Hydrogel showed good flame retardancy with values of heat release rate (HRR) below 5 kW/m² during the test time of 200 s, which is beneficial to the safety in the construction of hot work. Our findings confirmed that the hydrogel demonstrated an effective plugging effect in the simulated pipeline, and the residual hydrogel could be easily removed by injecting hot water. Hydrogels with thermo-reversibility can meet the plugging requirements for oil pipelines during hot work, simplifying the operation process and enhancing work efficiency.

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The work studied the formation and structure of (bio)PEC in mixtures of dilute chitosan and gelatin solutions at different pH and ratios of polymers and their ionized groups of z. Using the turbidimetry method for the chitosan and gelatin mixtures, it was found that stable scattering particles of (bio)PEC are formed in the pH range from 5 to 6.4 and with a polymer ratio above 1:5 (z = 0.29). The electrostatic interaction in the (bio)PEC structures was confirmed by ATR-FTIR spectroscopy. It was shown that during the formation of (bio)PEC in mixtures with pH = 5.5, a strong shift of the corresponding absorption bands relative to the initial polymers is observed. Studying the complexation and structure of these particles using the dynamic light scattering method of mixtures at pH = 3, the associative-dissipative character of the polymers interaction with the formation of soluble and unstable (bio)PEC dispersions was determined. It was observed that in mixtures with a pH = 5.5, the interaction becomes associative, which is accompanied by the formation of a (bio)PEC coacervate microphase at polymer ratios from 1:10 to 1:30 (in the z range from 0.58 to 1.73, respectively). Analysis of the structural properties of the coacervate microphase of (bio)PEC using dynamic light scattering and optical microscopy methods showed that with an increase in the proportion of an oppositely charged component of z ≥ 1, the isotropy of the polyelectrolyte binding process increases, which leads to suppression of the formation of loose heterogeneous coacervate particles of (bio)PEC.

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Direct conversion of solar energy into thermal energy by photothermal materials is the most efficient method among all solar energy conversion strategies. In this research, the photothermal performance of functionalized carbon nanotubes (CNTs) was investigated in both visible and near-infrared (NIR) regions (300–1000 nm), and their ability to evaporate water and also to kill cancer cells was investigated. CNTs with different concentrations of 0.03, 0.06, 0.25, and 0.5 g/L were dispersed in deionized water, and a maximum increase in the water temperature of 15 °C was measured in visible light. Also, a water surface evaporation rate of 0.6336 kg/h.m² with the photothermal conversion efficiency of 70.4% in the visible range was measured. The photothermal performance of CNTs in the NIR region was investigated with 808 nm laser radiation, and a water temperature increase of 46 °C with a conversion efficiency of 40.37% was measured. By increasing the laser power from 1 to 2 W/cm², the water temperature reached to 100 °C in less than 6 min. Also, the photothermal therapy performance of CNTs in killing HeLa cancer cells was investigated by the MTT method and found that CNTs can kill 93% of HeLa cancer cells within 10 min under laser radiation.‌

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