Colloid and Polymer Science最新文献

High internal phase emulsions (HIPEs) are commonly stabilized by a large amount of surfactants that should be removed after the polymerization of the continuous phase, and the resulting polyHIPEs from W/O HIPEs are usually brittle and chalky. Herein we report on an amphiphilic polymerizable polyurethane (PPU) macromolecular surfactant synthesized by polyaddition reaction of diisocyanates and polyols, which can well stabilize up to 88% internal phase volume of W/O HIPE with a content of only 5 wt% based the oil phase. Compared with the HIPEs stabilized by traditional surfactant Span 80, HIPEs stabilized by PPU at either room temperature or 70 °C are much more stable owing to the increased viscosity which can inhibit droplet coalescence. Moreover, the resulting polyHIPEs not only have several times higher mechanical properties than those stabilized by Span 80 but also have higher elasticity. The effects of concentration of PPU on the morphology and mechanical properties of the resulting polyHIPEs were investigated. It was found that with the increase of PPU content, the average void and window sizes decreased, while the compression strength increased. Cyclic compression tests were performed to examine reversible compressibility and durability of these polyHIPEs.

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The polymerizable polyurethane macromolecular surfactant (PPU) synthesized through the polyaddition reaction of diisocyanates and polyols can solely stabilize high internal phase emulsions (HIPEs), and highly interconnected macroporous polymer produced by the polymerization of HIPE stabilized with PPU, known as polyHIPE, can withstand large deformation compression with no visible cracks.

This study investigated the use of cellulose nanocrystals (CNC)/chitosan (Chit) polyelectrolyte complex as a stabilizing agent for Pickering emulsions. We demonstrated that chitosan reduces the surface charge of CNC improving the emulsification process. An optimal stabilizing complex containing 1% chitosan results in emulsions with minimal zeta potential (3.2 ± 0.3 mV), droplet size (2.8 ± 0.8 μm), and creaming index (19.8 ± 1.0%) values, along with high stability during storage, a change in pH, and high centrifugal forces (up to 2000 g). The study also showed that the maximum neutralized surface charge of the CNC in the CNC-Chit complex allows for effective adsorption on the surface of sunflower oil droplets, producing a denser stabilizing layer with a smaller droplet size. Additionally, chitosan addition is linked to improved stability and higher viscosity, with little dependence on ionic strength and temperature. Potentiometric titration revealed that compared with sulfated CNCs, five times less chitosan is needed to neutralize the negative surface charge of acetylated CNC. The wettability of a hydrophilic surface depends on the surface charge of the complex, and the wettability and adhesion performance increase with increasing chitosan content. Additionally, we showed that tuning the stabilizer composition can change the bioaccessibility of lipophilic compounds during oral administration.

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Three kinds of multiblock polyethylene oxide-polypropylene oxide (PEOm-PPOn for short) were synthesized using ethylene glycol as the initiated core via the living anionic polymerization. Respectively, the multiblock polyethers were named E340, E540, and E740 based on the block number (3, 5, 7) and the content of ethylene oxide (EO, 40 wt%), which were confirmed by the Fourier transform infrared (FT-IR), hydrogen nuclear magnetic resonance (¹H NMR), and gel permeation chromatography (GPC). Moreover, their bulk and solution properties, including dynamic modulus, rheological characteristic, viscosity, aggregation behavior, surface tension, steady-state fluorescence, solubility, and microemulsion performance were determined. The test results of rheological properties showed that these multiblock copolyethers behaved as the pseudo-plastic non-Newtonian fluids. Furthermore, it was found that their solubility and surface tension were gradually decreased with an increase of block numbers. Nevertheless, the dynamic modulus tended contrary trends. Research on the aggregation and micro-emulsion properties in aqueous solutions indicated that the value of critical micelle concentration (CMC) increased, and meanwhile the ability of solubilization and micro-emulsion formation deteriorated with increasing block numbers. In conclusion, their aggregation mechanism in aqueous solution was also given.

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An investigation is proposed for the Buongiorno model nanofluid flow within a converging as well as diverging channel which is inclined with the plane walls. The impact of magnetization is reported for the imposed of applied magnetic field along the normal direction of the flow. Additionally, the behavior of thermal radiation and the effect of binary chemical ration are implemented in the energy and concentration equation respectively. It is superimposed that both the channel walls are uniformly heated, and it is also assumed that concentration of the nanoparticles near the walls is considered as constant. However, the Cartesian coordinate system is imposed to describe the proposed designed flow problem. The formulated problem governed by nonlinear coupled partial differential equations is generalized and renovated to corresponding nondimensional form by implementing appropriate similarity rules. Further, the transformed equations are solved numerically using Runge-Kutta fourth order accompanied by shooting technique. The physical behavior of the standard factors involved in the problem is displayed graphically. Validation of the result is presented with an earlier study which shows a good correlation as well as convergence analysis of the proposed methodology. Further, the important outcomes of the proposed study are deployed as follows: the velocity distribution retards for the enhanced Reynolds number significantly; however, the Brownian motion is treated as a controlling parameter for the fluid temperature and reverse impact observed in case of fluid concentration.

Graphical Abstract

• The Buongiorno model nanofluid flow within a converging and diverging channel inclined with the plane walls is analysed.

• The behaviour of not only thermal radiation but also the effect of binary chemical ration is implemented.

• It is superimposed that both the channel walls are uniformly heated and it is also assumed that concentration of the nanoparticles near the walls is considered as constant.

• The transformed equations are solved numerically using Runge-Kutta fourth-order accompanied by shooting technique.

To investigate the impact of plasticizer functional groups on starch plasticization, three distinct plasticizers were selected in this study: ethylene glycol (EG), ethylenediamine (EDA), and ethylenebisformamide (EBF). Three models of the plasticizer/starch system were constructed using molecular dynamics (MD) simulations, and the analysis encompassed the computation of mean square displacement (MSD), radial distribution function (RDF), and hydrogen bonding energy for each system. Additionally, the proportions of simulation were used to prepare thermoplastic starch films, which were subsequently subjected to examinations such as DSC, XRD, FT-IR, SEM, and mechanical property testing. Comparative analysis of the simulation data from the three systems and the properties of the manufactured thermoplastic starch (TPS) established that the diverse functional groups of plasticizers significantly influenced starch plasticization. In different plasticizer functional group types, it was observed that hydroxyl groups in EG and amino groups in EDA predominantly form hydrogen bonds with hydroxyl groups in starch molecular chain. In contrast, amide groups in EBF can establish hydrogen bonds not only with hydroxyl groups of starch but also with ether bonds on the starch main chain, thereby resulting in more effective starch plasticization.

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To improve the efficiency of hydrophilic polymers in oil reservoirs, a method encapsulates the polymer within a protective shell, safeguarding the core polymer and enabling controlled release in demanding, high-temperature conditions. Poly(N-isopropylacrylamide) nanoparticles are encapsulated with polystyrene shells through emulsion polymerization in this study. Varying the amounts of shell monmer and crosslinking agents resulted thick, sphere-shaped shells with homogeneous morphology, which protects the core polymer and enabling controlled release. Structural and morphological properties are characterized using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (H¹NMR), dynamic light scattering (DLS), and scanning electron microscope (SEM) imaging. Increasing the styrene amounts lead to larger particles, while higher crosslinker amounts result in a narrower size distribution. Thermal testing indicates heat resistance up to 300 °C, suitable for enhanced oil recovery (EOR) applications. Rheological tests determine an optimal 30-day release for the PNIPAM core, with the CS polymer showing increased viscosity under harsh conditions. The colloidal stability model estblished by Derjaguin, Landau, Verwey, and Overbeek (DLVO theory) and experimental results demonstrate good stability and energy barriers at room temperature, but decreased stability and increased agglomeration at higher temperatures. Thickening the styrene shell leads to particle agglomeration and unsuitable stability. The study confirms the effectiveness of the model in analyzing CS colloidal latex systems.

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Aqueous liquid suspensions of high aspect ratio 2D clay nanosheets were investigated using small angle X-ray scattering (SAXS). The high aspect ratio of synthetic fluorohectorite clays allows for investigation of liquid crystalline orientational order for relatively large nanosheet spacings, in the range which can produce structural coloration, thus providing two handles for determining the nanosheet spacings: SAXS and visible color. Various clay concentrations were investigated, and good agreement with previous work on structural coloration from such suspensions was obtained. Particular attention is given to the confinement caused by the container geometry, where both cylindrical and flat confinements were investigated. In both cases, the SAXS data suggest coherent regions that have a nematic inter-orientational distribution that surprisingly is linked to the container geometry, which apparently determines the efficiency of packing of the suspension. For both geometries, the analysis suggests that these coherent regions have a 1D lamellar periodic intra-structure with uniform nanosheet spacing determined by the clay concentration and a typical correlation length in the range of 200 to 500 nm.

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We embarked on an investigation with potential implications for studying blood flow within the cardiovascular system; keeping this application in mind, this investigation aims to provide numerical evaluations for a complex problem involving MHD flow, chemical reactivity, and energy transfer of a Maxwell fluid within a channel. The governing equations for momentum, concentration, and energy are renovated into ODEs for concentrated analysis using a similarity transformation. Dimensionless velocity, temperature, and concentration fields corresponding to steady motions of Maxwell fluid over a channel are numerically recognized using the bvp4c inbuilt software in MATLAB. We validated our results with existing work to check the gained results and got an excellent agreement. The impression of physical parameters on fluid motion is plotted and debated. The quantitative outcome of this study is that the Deborah number surges, and both velocity and temperature experience enhancement while the concentration within the fluid diminishes. This knowledge can be applied to various fields, such as material processing, biomedical engineering, and environmental sciences, to optimize processes and design systems accordingly. The outcomes and key findings of this study indicate that concentration distribution declines with the introduction of a chemical reaction and a complex Schmidt number. Additionally, the quantitative results of this learning are that the impression of the magnetic parameter is observed, resulting in reduced velocity and temperature profiles, while concentration profiles exhibit an increase across the entire domain. Furthermore, the rise in the Reynolds number corresponds to an escalation in the temperature outline.

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