Continuous Network Structures Research Articles

Construction of polydopamine functionalized porous carbon network structure in polymer composites for excellent mechanical and electromagnetic interference shielding properties

Structural and functional integrated lightweight polymer-based composites with excellent mechanical and electromagnetic interference (EMI) shielding properties are urgently demanded in the field of advanced aerospace field. Effective design to construct the interfacial porous microstructures is crucial yet remains highly challenging for maximum EMI shielding effectiveness (SE) while improving the strength of composites. Herein, novel interfacial continuous network structures are constructed based on the in-suit synthesis of porous carbon network on the carbon fibers and chemical functionalized with polydopamine (PDA) to achieve simultaneous improvement of mechanical properties and EMI SE. Results indicate that the construction of active porous carbon networks significantly improves the surface activity and wettability of carbon fibers, which is conducive to enhancing the interfacial strength of the composites. Owing to the synergistic effect of physical enhancement for porous carbon and chemical reinforcement for PDA, the bending strength of the modified composite reaches 138.9 MPa, and the wear rate decreases by 82.9 %, demonstrating excellent mechanical properties. It is worth noting that the EMI SE reaches more than 62 dB in the X-band when the thickness of the modified composite is only 0.4 mm, showing excellent EMI shielding performance. Most importantly, this study provides solid basic knowledge of the interfacial structure design of composites, which is favorable for obtaining expected mechanical and EMI shielding performances and offers strong potential for applications in structural components of the aerospace and electronic equipment field.

Single Ultrasonic-Assisted Washing for Eco-Efficient Production of Mackerel (Auxis thazard) Surimi.

This study highlights a promising single washing method for producing dark-fleshed mackerel surimi aided by ultrasonication in conjunction with cold carbonated water containing 0.6% NaCl and mixed antioxidants (0.5% EDTA/0.2% sodium erythorbate/0.2% sodium tripolyphosphate) (CSA). Different washing periods (5, 10, and 15 min) with and without ultrasound were tested. Unwashed mince (A1) and conventional water-washed surimi (10 min/cycle, 3 cycles) (A2) were used as controls. A3, A4, and A5 were subjected to ultrasound-assisted washing for 5, 10, and 15 min, respectively, whereas A6, A7, and A8 had non-ultrasound-assisted washing for 5, 10, and 15 min. Results showed that the surimi yield decreased as the ultrasonic treatment time increased from 5 to 15 min (p < 0.05). Increased ultrasonic time resulted in greater protein denaturation, protein oxidation, myoglobin removal, and lipid oxidation in surimi (p < 0.05). Surimi produced by CSA ultrasonication for 5 min (A3), on the other hand, had a comparable overall quality to A2 surimi (p > 0.05). The correspondence gel (A3) outperformed the control gel (A2) in terms of gel strength, whiteness, and water-holding capacity (p < 0.05). The formation of regularly continuous, more organized, and smooth network structures in surimi gel was observed in A2 and A3 gels, whereas sparse and larger pore sizes were noticed in surimi gels produced by longer ultrasonic treatment. All of the surimi gels had identical FTIR spectra, indicating that the functional groups of the protein gel were consistent throughout. As a result, a single 5 min CSA-ultrasonic washing could potentially yield surimi of comparable quality to conventional washing. This could pave the way for the development of dark-fleshed fish surimi, which would require less washing time and produce less waste water.

Formation mechanism of cold-set bitter apricot kernel protein isolate-gellan gum binary gels with excellent freeze-thaw stability

Binary gels with various microstructures, including apricot kernel protein isolate-gellan gum gels with high freeze-thaw stability, were obtained by combining transglutaminase covalent cross-linking and gellan gum modification. Adding 0–0.1% gellan gum (w/w) can form continuous protein network structures dominated by covalent networks and disulfide bonds. In addition to covalent cross-linking, the increase in the strength of hydrophobic and electrostatic interactions at gellan gum concentrations below 0.2% (w/w) facilitated the formation of a bicontinuous network (AGG3). When excess gellan gum was added (0.03%, w/w), gellan gelation occurred in the system, leading to the formation of heterogeneous aggregated structures (AGG4). Confocal laser microscopy revealed a dense porous structure in the continuous protein network after freeze-thaw treatment, and AGG4 showed heterogeneous and loose aggregated microstructure, while the bicontinuous network structure was maintained. The water holding capacity of AGG3 was increased by 21.36% after freezing compared with the gels without gellan gum, and AGG3 maintained high hardness and springiness. Low-field nuclear magnetic resonance and magnetic resonance imaging showed that the bicontinuous network was more conducive to the tethering ability and uniform distribution of hydrogen protons than the continuous network structure of proteins. Therefore, AGG3 exhibited excellent freeze-thaw stability.

Study on the mechanism of various exogenous proteins with different inhibitions on wheat starch digestion: From the distribution behaviors of protein in the starch matrix

This study aimed to compare the effect of various exogenous proteins on wheat starch (WS) digestion and assess the relevant mechanisms based on the distribution behaviors of exogenous proteins in the starch matrix. Rice protein (RP), soy protein isolate (SPI), and whey protein isolate (WPI) all effectively suppressed the rapid digestion of WS but with different modes. RP increased the slowly digestible starch content, while SPI and WPI increased the resistant starch content. Fluorescence images showed that RP aggregated and competed for effective space with starch granules, while SPI and WPI formed continuous network structures among the starch matrix. These distribution behaviors endowed different reductions in starch digestion by influencing the gelatinization and ordered structure of starch. Pasting and water mobility results suggested all exogenous proteins inhibited the water migration and swelling of starch. Simultaneously, X-ray diffraction and Fourier transform infrared spectroscopy analysis showed that exogenous proteins improved the ordered structures of starch. RP had a more significant effect on the long-term ordered structure, while SPI and WPI had a more effective effect on the short-term ordered structure. These findings will enrich the theory of exogenous protein inhibiting starch digestion and inspire the applications in low-glycemic index food.

Examination on aerogel based on the heat transfer characteristics of nanotechnology

With the rapid development of global industrialization, the research and development of new thermal insulation materials has great social and economic significance for national development and social progress. Due to the porous network structure of nanotechnology, the porosity of aerogel is 80–99.8%, the thermal conductivity can be as low as 0.013 w/(m k) at room temperature. It is the best insulation material by far, it has important value in the fields of aerospace, petrochemical, electric metallurgy, shipbuilding, precision instruments and so on. This paper is based on aerogel nanotechnology materials at home and abroad. In order to solve the problem of the study on heat transfer characteristics based on nanotechnology is not perfect, and the calculation model of solid phase thermal conductivity coefficient and total thermal conductivity of complex nanotechnology structure is not accurate enough. Through a heat transfer calculation method suitable for nanotechnology to conduct more detailed and in-depth research on these issues, introduces and analyzes the development of the equivalent thermal conductivity calculation model of Novel Aerogel nanotechnology insulation material in recent years. And analyzed The heat transfer characteristics and thermal insulation principle of nanotechnology aerogel by using equivalent thermal conductivity calculation model of aerogel nanotechnology insulation material. Research indicates: For aerogel nanotechnology materials, Use heat transfer calculation method aerogel nanotechnology insulation materials can be well calculated using a heat transfer calculation method that suitable for nanotechnology can calculate the equivalent thermal conductivity of aerogel nanotechnology insulation material very well; nanotechnology particles and aerogel meshes and continuous spatial network structures are reason for the very low thermal conductivity of aerogels; The heat transfer of the material is mainly achieved by convection, radiation and heat transfer. So it is possible to reduce the thermal conductivity from the heat transfer path of the material.

One-pot synthesis of Carbon nanotube reinforced graphene aerogels and their applications in electromagnetic wave attenuation

Recently, hydrothermal self-assembly fabrication techniques for three-dimensional (3D) graphene aerogels have attracted more and more research attention in developing ideal electromagnetic wave absorbing materials. However, the defect of poor mechanical stability is difficult to overcome due to the disordered weak connection of graphene sheets during self-assembly, which also greatly restrict its practical application value in the field of electromagnetic wave absorbing materials. Here, we prepared a CNTs/graphene aerogel (CGA) with high mechanical stability which composed of one-dimensional (1D) CNTs and two-dimensional (2D) graphene sheets through a facile one-pot hydrothermal strategy. The thoroughly dispersed CNTs inserted on the graphene sheets to form continuous network structures, which not only improved the mechanical properties, but also adjusted the electrical conductivity of graphene sheets, thus enhancing the microwave absorption performance. The CGA-3 exhibits the best mechanical stability as it can withstand a weight of 70 g which is ~800 times of its own weight. Meanwhile, the CGA-3 shows the best electromagnetic wave absorption performance, where the minimum reflection loss could reach −54dB, and the effective absorbing bandwidth is 6.3 GHz (11.7–18 GHz) with an absorbent thickness of 2.3 mm, covering the whole Ku band. This work confirms that the CNTs/graphene aerogels are expected to become ideal absorbers, which is meaningful to extend the structural enhancement and practical application of 3D graphene-based electromagnetic wave absorbing materials.

Investigation of a high temperature gel system for application in saline oil and gas reservoirs for profile modification

The deeper the burial of the oil and gas reservoir, the higher the temperature of the oil and gas reservoir. When profile adjustment of water injection wells, plugging of oil production wells (gas production wells) and temporary plugging or killing of oil production wells (gas production wells) are required, the higher the temperature resistance of the plugging agent (above 150 °C) is required. In addition, high temperature resistant plugging agents should also be used in profile control or water plugging in reservoirs (120°C–200 °C) that are thermally recovered by steam injection or in situ combustion. It is of great importance to develop a high-temperature-resistant gel plugging system to fulfill the requirements of deep buried high-temperature oil or gas reservoirs or thermal recovery high-temperature oil reservoir operations.A gel system formed by the terpolymer (L-1) and a new cross-linking system (HB-1) was developed, and its properties were systematically studied in the condition of extremely high temperature. Studies have shown that the gel system could form stable continuous 3D network structures in high temperature (120°C–200 °C) and thus have an excellent long-term thermal stability.The gel system can adjust the strength by changing the concentration of the terpolymer (0.05%–1%) and the crosslinker (0.05%–1%), which can achieve different construction requirements. Compared with the conventional high-temperature-resistant gel, the cross-linking system HB-1 contains 4 hydroxyl groups (–CH2OH), it can crosslink with 4 amide groups (–CONH2) on the terpolymer. Therefore, this gel system can form a smaller grid size of 3D network structures (less than 5 μm), so it has stronger temperature resistance and better long-term thermal stability. When the temperature is 200 °C, the grid size of network structure is about 10 μm, but the strength of the gel system can still be maintained at code F-G. When the salinity of the water solution is 200,000 mg/L, the gel system on the contact surface can still maintain a small grid size of 3D network structures (about 10 μm). The gel system could maintain most of the initial viscosity and viscoelasticity, even after experiencing the mechanical shear or the porous-media shear. A gel system with strength F can still be formed after shearing by the pore media of 10 sand-packed tubes, and the plugging rate of each sand-packed tube exceeds 97%. It can be found by scanning electron microscope pictures that the gel system can be very firmly attached to the pore media, which can achieve profile adjustment of the formation. The gel system could have great potential in the application of high temperature oil or gas reservoirs.

Enhancement of resistant starch content in modified rice flour using extrusion technology

AbstractBackground and objectivesThe present study was conducted with an aim to modify rice flour for enhancement of resistant starch content using extrusion technology. The effects of feed moisture, barrel temperature, and screw speed on resistant starch (RS), predicted glycemic index (pGI), glycemic load (GL), and instrumental color (L*, a*, and b* values) were investigated using response surface methodology.FindingsRS, pGI, GL, L*, a*, and b* varied between 4.91%–6.83%, 73.20–76.90, 48.0–53.04, 70.43–85.95, 6.92–10.32, and 15.09–30.81, respectively. Models obtained for these parameters were highly significant (p ≤ .0028). Significantly (p &lt; .05) higher RS content (6.20%) and lower pGI and GL values (75.10 and 50, respectively) were recorded in modified rice flour (MRF) as compared to native rice flour (NRF). Lower values of pasting properties and higher thermal properties were recorded in MRF than NRF. Scanning electron micrographs showed continuous and dense network structures in MRF, whereas ungelatinized granules were evident in NRF.ConclusionExtrusion processing caused significant changes in the digestibility of rice flour which increased the RS content and decreased the pGI in MRF. 30% moisture content, 140°C barrel temperature, and 70 rpm screw speed were found most feasible conditions to enhance RS content in MRF.NoveltyThe extrusion of rice flour without a die proved to be a unique way to produce pregelatinized rice flour with higher RS and lower pGI. MRF can be explored for development of functional foods especially for diabetic and celiac disease patients.

Investigation of a high temperature gel system for application in saline oil and gas reservoirs for profile modification

The deeper the burial of the oil and gas reservoir, the higher the temperature of the oil and gas reservoir. When profile adjustment of water injection wells, plugging of oil production wells (gas production wells) and temporary plugging or killing of oil production wells (gas production wells) are required, the higher the temperature resistance of the plugging agent (above 150 °C) is required. In addition, high temperature resistant plugging agents should also be used in profile control or water plugging in reservoirs (120°C–200 °C) that are thermally recovered by steam injection or in situ combustion. It is of great importance to develop a high-temperature-resistant gel plugging system to fulfill the requirements of deep buried high-temperature oil or gas reservoirs or thermal recovery high-temperature oil reservoir operations.A gel system formed by the terpolymer (L-1) and a new cross-linking system (HB-1) was developed, and its properties were systematically studied in the condition of extremely high temperature. Studies have shown that the gel system could form stable continuous 3D network structures in high temperature (120°C–200 °C) and thus have an excellent long-term thermal stability.The gel system can adjust the strength by changing the concentration of the terpolymer (0.05%–1%) and the crosslinker (0.05%–1%), which can achieve different construction requirements. Compared with the conventional high-temperature-resistant gel, the cross-linking system HB-1 contains 4 hydroxyl groups (–CH2OH), it can crosslink with 4 amide groups (–CONH2) on the terpolymer. Therefore, this gel system can form a smaller grid size of 3D network structures (less than 5 μm), so it has stronger temperature resistance and better long-term thermal stability. When the temperature is 200 °C, the grid size of network structure is about 10 μm, but the strength of the gel system can still be maintained at code F-G. When the salinity of the water solution is 200,000 mg/L, the gel system on the contact surface can still maintain a small grid size of 3D network structures (about 10 μm). The gel system could maintain most of the initial viscosity and viscoelasticity, even after experiencing the mechanical shear or the porous-media shear. A gel system with strength F can still be formed after shearing by the pore media of 10 sand-packed tubes, and the plugging rate of each sand-packed tube exceeds 97%. It can be found by scanning electron microscope pictures that the gel system can be very firmly attached to the pore media, which can achieve profile adjustment of the formation. The gel system could have great potential in the application of high temperature oil or gas reservoirs.

Effect of post-weld heat treatment on microstructure and mechanical properties of 7055 aluminum alloy electron beam welded joint

The spray forming 7055 aluminum alloy is welded by electron beam welding (EBW). After welding, the single solution treatments under different temperatures and then aging treatment (STA) and the stepped solution treatment and then aging treatment (SSTA) are carried out for the welded joints respectively. The effect of different post-weld heat treatment (PWHT) procedures on the microstructure and mechanical properties of welded joints is systematically investigated. Results show that, in as-welded condition, the fusion zone mainly consists of α-Al phase, and there are some precipitated phases such as Mg32(Al,Zn)49, Al7Cu2Fe, Al2CuMg, and a small amount of phase MgZn2 in weld metal. After PWHT, the continuous network structures at grain boundary disappear. There are only a few isolated particle phases at grain boundary, and many ellipsoidal η′ phases and rod-like η phases are precipitated within grains. The mechanical property of welded joint is improved after PWHT. Compared with that of in STA condition, the strengthening effect to welded joint is more obvious after SSTA. In SSTA condition, the hardness of weld zone is close to that of base metal (BM), and the tensile strength of welded joint reaches 486.2 MPa, which is 85.6% of that of BM. There are many equiaxed dimples on the tensile fracture surface, and the joint mainly presents the characteristic of ductile fracture.

Vertically aligned dopamine-reduced graphene oxide with high thermal conductivity for epoxy nanocomposites

Designing ordered fillers arrangement and superior interfacial adhesion between fillers and matrix can improve the thermal conductivity (TC) of composites. Here, bioinspired dopamine chemistry was firstly used to reduce graphene oxide (GO) and introduce polydopamine nanoparticles on the surface of GO. Then, a well-aligned epoxy/reduced GO films (EP/RGFs) nanocomposites were prepared via the simple vacuum impregnation. Compared with the random distribution of fillers in a traditional blending composite, fillers were selectively distributed in matrix and continuous thermal conductive network structures were constructed in this strategy. As a result, the nanocomposite exhibited a high TC of 0.913 W m−1 K−1 which is 4.8 times higher than pure EP. In addition, curing kinetics showed that RGFs were similar to an amine-type curing agent that reacted with EP and bonded them tightly, and its nanocomposites reaction activation energy is lower than that of pure EP. These results indicated RGFs possessed excellent interface compatibility with EP and suppressing effectively the phonon scattering at the EP–RGFs interface. Cooling experiments showed that nanocomposites can reduce by about 10 °C for a hot source (80 °C), demonstrating it can transfer efficiently heat energy from the heat source. This study provides an effective method for the preparation of high-performance thermal management composites.

Microstructural, electronic, and mechanical properties of L12 ordered Al3Er and Al3Yb intermetallics: an experimental and first-principles calculations

The microstructural, electronic, and mechanical properties of L12 ordered Al3Er and Al3Yb intermetallics were analyzed by x-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and first-principles calculations based on the density functional theory (DFT). The results show that the Al3Er intermetallic presents short rod-like structures in the Al-10 wt% Er alloy while the Al3Yb intermetallic presents continuous network structures in the Al-10 wt% Yb alloy. The calculated lattice constants are highly consistent with available experimental measurements, with a deviation less than 1.9%. The results of negative cohesive energy () of the Al3Er and Al3Yb intermetallics indicate that they are both stable structures, while the structural stability of Al3Er intermetallic is stronger than that of Al3Yb. Further analysis on the bonding of electronic structures shows that Al3Er intermetallic is a higher stable structure than Al3Yb. It is found that Al3Er and Al3Yb intermetallics are brittle and the plasticity of Al3Yb intermetallic is stronger than Al3Er. From the results of the Young’s modulus, the Al3Er and Al3Yb intermetallics have strong anisotropic characteristics but the difference between Al3Er and Al3Yb intermetallics is small. According to the calculated Debye temperature, the Al3Er intermetallic exhibits relatively higher thermal conductivity and stronger covalent bonds.

Preparation of Graphene Aerogel with High Mechanical Stability and Microwave Absorption Ability via Combining Surface Support of Metallic-CNTs and Interfacial Cross-Linking by Magnetic Nanoparticles.

The preparation of graphene aerogel by hydrothermal or chemical reduction has been one of the hot topics of research. But in the process of assembly, the random weak connection of GO flakes leads to irreversible deformation under compression, and the mechanical stability of aerogel based on graphene is one of its drawbacks that is hard to overcome. Here, a novel method to prepare graphene aerogel with high mechanical stability was proposed via combining surface support brought by metallic-CNT networks and interfacial cross-linking of GO sheets achieved by nanoparticle selective absorption. Thoroughly dispersed metallic-CNTs absorbed on the basal plane of GO flakes formed continuous network structures, which not only improve the mechanical performance of flakes but also provide steric effects to impel the adsorption of metallic oxide magnetic nanoparticles concentrated on the edge of GO flakes, thereby guaranteeing the interfacial connection of adjacent rGO flakes by nanoparticle cross-linking. Meanwhile, the surface and interface reinforce approach can greatly improve the electrical conductivity and mechanical stability of composites. Owing to the lightweight, abundant interface, high electrical conductivity, combined with the superparamagnetic properties brought by the magnetic nanoparticles, composite aerogel with high mechanical stability and excellent microwave absorption was achieved, of which the effective absorption bandwidth of the aerogel is 4.4-18 GHz and the maximum value can reach -49 dB. This approach could not only be used to prepare microwave absorption materials with light weight and high performance but also be meaningful to enlarge the construction and application of carbon-based materials.

Development of a High-Temperature-Resistant Polymer-Gel System for Conformance Control in Jidong Oil Field

Summary The PG Reservoir in Jidong Oil Field is at a depth of approximately 4500 m with an extremely high temperature of approximately 150°C. The average water cut has reached nearly 80%, but the oil recovery is less than 10% after only 2 years of waterflooding process. It is of great importance to develop a high-temperature-resistant plugging system to improve the reservoir conformance and control water production. An in-situ polymer-gel system formed by the terpolymer and a new crosslinker system was developed, and its properties were systematically studied under the condition of extremely high temperature (150°C). Suitable gelation time and favorable gel strength were obtained by adjusting the concentration of the terpolymer (0.4 to 1.0%) and the crosslinker system (0.4 to 0.7%). An increase of polymer and crosslinker concentration would decrease the gelation time and increase the gel strength. The gelant could form continuous 3D network structures and thus have an excellent long-term thermal stability. The syneresis of this gel system was minor, even after being heated for 5 months at the temperature of 150°C. The gel system could maintain most of the initial viscosity and viscoelasticity, even after experiencing the mechanical shear or the porous-media shear. Core-flow experiments showed that the gel system could have great potential to improve the conformance in Jidong Oil Field.

Heteropoly acids triggered self-assembly of cationic peptides into photo- and electro-chromic gels.

A series of cationic peptides with alternating lysines and hydrophobic residues were designed and synthesized. These kinds of short peptides with protonated lysines can complex with anionic heteropoly acids (HPAs) to form a stable gel in water/ethanol mixed solution. Circular dichroism spectroscopy showed that the short peptides adopted a mixed conformation (β-sheet and random-coil) within the gel matrix. Scanning and transmission electron microscopy revealed that the heteropoly acids, acting as nanosized cross-linkers, first initiated the self-assembly of the cationic peptides into spherical nanostructures. Then these nanospheres accumulated with each other through hydrogen bonds and hydrophobic interactions to form large sheet-like assemblies, which further interconnected with each other forming continuous 3D network structures. Fourier-transform infrared spectroscopy showed that the structural integrity of the HPAs was maintained during the gelation process. The resultant hybrid gels showed reversible photo- and elecrtro-chromic properties. X-ray photoelectron spectroscopy revealed that the hybrid gels, capable of persistent and reversible changes of their colour, are attributed to the intervalence charge-transfer transition of the HPAs. Reversible information writing and erasing were demonstrated through a repeated photo-lithograph or electric stimuli without significant loss of the gel performance.

Light-induced vibration characteristics of free-standing carbon nanotube films fabricated by vacuum filtration

In this paper, we fabricated carbon nanotube (CNT) films with different thickness by vacuum filtration method, and the films were separated from Mixed Cellulose Ester membranes with burn-off process. The thickness of CNT films with different concentrations of CNTs 50 mg, 100 mg, 150 mg, and 200 mg are 10.36 μm, 20.90 μm, 30.19 μm, and 39.98 μm respectively. The CNT bundles are homogeneously distributed and entangled with each other, and still maintain 2D continuous network structures after burn-off process. The optical absorptivity of the films is between 84% and 99% at wavelengths ranging from 400 nm to 2500 nm. Vibration characteristics were measured with the Fabry-Perot (F-P) interferometer vibration measurement system. CNT films vibrate only under the xenon light irradiating perpendicularly to the surface. Vibration recorded by Fabry-Perot interferometer is considered to be caused by the time-dependent thermal moment, which is due to the temperature differences of two sides of CNT films. The vibration frequency spectrums between 0.1 ∼ 0.5 Hz were obtained by the Fast Fourier Transform spectra from time domain to frequency domain, and showed a linear relationship with films thickness, which is in accordance with theoretical model of thermal induced vibration.

Modeling of the atomic structure and electronic properties of amorphous GaN1−xAsx

Chemically ordered 250-atom models for amorphous GaN1−xAsx alloys in the concentration range of 0.17<x<0.75 have been studied with density functional theory simulations, starting with initial continuous random network structures. The analysis of network topology has been achieved by examining partial-pair correlation functions, bond angle distributions, ring statistics and average coordination numbers. The electronic properties of amorphous GaN1−xAsx alloys have been estimated by means of electronic density states (EDOS) and inverse participation ratios (IPR). Our calculations indicate that the introduction of As into GaN reduces the bond angle disorder. According to our ring analysis the 250atom a-GaN1−xAsx model has a disordered tetrahedral characteristic confirming the fact that continuous random network (CRN) can provide an ideal initial structure. The study of EDOS and IPR proves that the bandgap of a-GaN1−xAsx gets narrower with increasing As concentration, which is in good agreement with the experimental results and the band anti-crossing model.

Rheological behavior of an acrylamide-based terpolymer with p-vinylbenzyl-terminated octylphenoxy poly(ethylene oxide)

A comb-like associating terpolymer PAOE was synthesized from acrylamide (AM), sodium 2-aciylamido-2-methylpropane sulphonate (NaAMPS) and a novel macromonomer: p-vinylbenzyl-terminated octylphenoxy poly(ethylene oxide) (VOE, degree of polymerization: 4—using aqueous free-radical copolymerization technique. The polymer chains were still comparatively extended in the brine solutions at low polymer concentrations. This leaded to the formation of continuous network structures via the intermolecular hydrophobic associations of the octylphenyl groups in despite of the addition of NaCl. As a result, PAOE predominantly exhibited significant elastic characters in brine solutions at 0.5–9 g/dL NaCl, as well as in aqueous solutions. The viscous and elastic character decreased slightly with increasing temperature from 25 to 45°C for the PAOE brine solution with 0.5 g/dL NaCl. The PAOE aqueous and brine solutions displayed obvious shear thickening behavior upon consecutive steady shear cycles. The brine solution also showed the excellent thickening properties, salt-thickening behaviors twice, and resistance to salt.

Cholesterol-based low-molecular mass gelators towards smart ionogels

Ionic liquids are solvents of future. One of the promising methods to boost their uses is to solidify them in a physical way but with little interruption of their properties. It is therefore of interest to create gels of ionic liquids by using low-molecular mass compounds as gelators (LMMGs). Herein, we report a number of ionic liquid gels (ionogels) of which specially designed and synthesized cholesteryl derivatives were employed as gelators. The ionogels as obtained are thermo-reversible. In particular, the one with 1-butyl-3-methylimidazolium tetrafluoroborate (IL2) as solvent and a cholesteryl derivative containing a D-phenylalanine residue (1D) as a gelator is very stable both in neutral and acidic mediums as demonstrated by a yield stress of 76 Pa for a self-standing cylinder of the ionogel. Furthermore, the ionogel can be easily converted into a hydrogel via simple replacement of the solvent with water in situ. More interestingly, the conversion is reversible, a phenomenon never reported before. At the same time, the critical gelation concentration (CGC) of 1D for IL2 is only 0.06%, w/w, which is almost the lowest value reported for ionogels till now, and falls into the category of “super-gelator”. Magnetization of the ionogel has been realized by introduction of micro-/nano-Fe3O4 particles. As expected, the magnetic gel as obtained is responding to external magnetic field. Specifically, it changes into fluid with the presence of a magnetic field exceeding certain strength, and retains to gel upon removing the magnetic field and with a treatment of sonication and heating–cooling cycle. SEM and TEM observations revealed the continuous fibrous network structures of the molecules of the gelator in the ionogels. To the best of our knowledge, this is the first report on ionogels possessing stimulus-responsive properties, good mechanical strength, and super-gelation talent.

Association in Unsalted and Brine Solutions of a Water-Soluble Terpolymer with p-Vinylbenzyl-Terminated Octylphenoxy Poly(ethylene oxide)

An associating terpolymer (PAOE) of acrylamide (AM), sodium 2-acrylamido-2-methylpropane sulphonate (NaAMPS), and a novel macromonomer: p-vinylbenzyl-terminated octylphenoxy poly(ethylene oxide) (VOE, degree of polymerization: 4) was synthesized by aqueous free-radical copolymerization. The PAOE polymer exhibited excellent thickening properties in unsalted and brine solutions. The electrostatic shielding of repulsive interactions of the polymer was much weaker than that of the linear associating polymers with small hydrophobic monomers. This brine solution exhibited unexpected salt-thickening behaviors twice, and good resistance to salt and ageing. The intermolecular hydrophobic association in unsalted and brine PAOE solutions, as functions of polymer and NaCl concentration, were characterized by fluorescence spectroscopy. With the addition of NaCl, the polymer chains were comparatively extended and continuous network structures were formed via the intermolecular hydrophobic association in brine solutions as well as in unsalted solutions at 0.15–0.25 g⋅dL−1 PAOE, as observed by a scanning electron microscope (SEM).