Polymerization Of Acrylamide Research Articles

Синтез и свойства привитых сополимеров ксантана и глюкоманнана с акриловыми мономерами

Graft copolymers of polysaccharides with acrylic monomers combine biodegradability, biocompatibility, the environmental friendliness of natural polymers and the increased thermal stability, chemical and mechanical resistance of synthetic polymers. This paper describes our search and analysis of the literature in English for 2002–2022 devoted to the graft polymerization of acrylamide, acrylic acid and 2-acrylamido- 2-methylpropanesulfonic acid onto xanthan and glucomannan macromolecular chains. It has been found that the synthesis of grafted copolymer chains proceeds by a radical polymerization mechanism using thermal homolytic decomposition of the initiator or microwave irradiation, or radiation initiation and frontal polymerization in some cases. Depending on the method of the reaction, the synthesis time of a graft copolymer varies from several minutes to several hours. The influence of the synthesis conditions and parameters on the monomer conversion, structure and properties of the resulting polymer has been considered. It has been found that decreasing the polysaccharide/monomer ratio and increasing the initiator concentration raise the efficiency and degree of grafting. Several methods for characterization of graft copolymers are discussed, including: IR spectroscopy to analyze the chemical structure of a sample, scanning electron microscopy to characterize structure, supramolecular ordering and porosity, differential thermal analysis to evaluate thermal effects and thermal stability. The effect of the synthesis conditions and the pH of the sorption medium on the water absorption and sorption capacity of this class of graft copolymers are discussed. The broad potential of graft copolymers for repeated cycles of absorption and release of liquid medium without loss of functional properties has been found. This opens prospects for the use of graft copolymers of xanthan and glucomannan with acrylic monomers as materials for water purification from metal ions and cationic dyes, targeted delivery and prolonged action of drugs and wound coatings for wound treatment.

Controlled Polymerization of Acrylamide via One-Pot and One-Step Aqueous Cu(0)-Mediated Reversible-Deactivation Radical Polymerization.

Copper-catalyzed controlled polymerization of acrylamide (AM) has always been a challenge, which typically exhibits low monomer conversion and broad molecular weight distribution (MWD) or requires complex/multistep reaction procedures, due to the highly active nature of the AM radical and its side reactions. To overcome the above challenges, herein, we report the successful synthesis of well-defined polyacrylamide (PAM) via a facile one-pot and one-step aqueous Cu(0)-mediated reversible-deactivation radical polymerization (RDRP). The results of this strategy show that strong deactivation control is the key for the controllability of AM RDRPs, which depends on the equilibria of polymerization and mutual conversion of different copper species. With the fast-propagating monomer AM, extra addition of CuII into the reaction system is an effective way to enhance deactivation. Based on this kinetically controlled strategy, well-defined PAMs with narrow molecular weight distributions (MWDs) and varied molecular weights (Mws) were successfully achieved.

Conceptualization and Investigation of Multicomponent Polymer Networks as Prospective Corticosteroid Carriers.

Dexamethasone (DXM) is a highly potent and long-acting synthetic glucocorticoid with anti-inflammatory, anti-allergic, and immunosuppressive effects. However, the systemic application of DXM can cause undesirable side effects: sleep disorders, nervousness, heart rhythm disorders, heart attack, and others. In the present study, multicomponent polymer networks were developed as potential new platforms for the dermal application of dexamethasone sodium phosphate (DSP). First, a copolymer network (CPN) comprising hydrophilic segments of different chemical structures was synthesized by applying redox polymerization of dimethyl acrylamide onto poly(ethylene glycol) in the presence of poly(ethylene glycol) diacrylate (PEGDA) as a crosslinker. On this basis, an interpenetrating polymer network structure (IPN) was obtained by introducing a second network of PEGDA-crosslinked poly(N-isopropylacrylamide). Multicomponent networks obtained were characterized by FTIR, TGA, and swelling kinetics in different solvents. Both CPN and IPN showed a high swelling degree in aqueous media (up to 1800 and 1200%, respectively), reaching the equilibrium swelling within 24 h. Additionally, IPN showed temperature-responsive swelling in an aqueous solution as the equilibrium swelling degree decreased considerably with an increase in the temperature. In order to evaluate the networks' potential as drug carriers, swelling in DSP aqueous solutions of varied concentration was investigated. It was established that the amount of encapsulated DSP could be easily controlled by the concentration of drug aqueous solution. In vitro DSP release was studied in buffer solution (BS) with pH 7.4 at 37 °C. The results obtained during DSP loading and release experiments proved the feasibility of the developed multicomponent hydrophilic polymer networks as effective platforms for potential dermal application.

Solar–Thermal Conversion Properties of Bilayered Porous Solar Absorbers Fabricated by Mixed Halloysite/Palygorskite Clays

In recent years, solar absorbers have received widespread attention, however, large‐scale preparation is difficult to achieve for many absorbers, and the raw materials are expensive. Halloysite (HNTs) and palygorskite (PAL) have the advantage of abundant reserves and low prices. Herein, solar absorbers with bilayer and porous features are prepared from mixed clays of HNTs and PAL; further studies focused on the solar–thermal conversion efficiency of the absorbers. The mixed clays are gelated by aqueous polymerization of acrylamide and N, N′‐methylene bisacrylamide, then the surface of the gel is carbonized to obtain the double‐layer solar absorbers (F‐HNTs/PAL). The F‐HNTs/PAL shows excellent thermal stability with a weight‐loss ratio of 13% at 1,000 °C, good mechanical properties with a compressed strength of up to 200 KPa at 80% strain, abundant porosity with an adsorption pore volume of 0.057 cm3 g−1, and low thermal conductivity (0.206 W m−1 K−1). Under 1 sun illumination, the F‐HNTs/PAL has a higher vapor rate of 1.215 kg m−2 h−1 that equals 84% solar‐to‐vapor efficiency, which is much more than 57% of F‐HNTs prepared by the same methods, but the F‐HNTs/PAL shows unique thermal stability and mechanical property.

EXPERIENCE IN USING PRE-CROSSLINKED POLYMER SYSTEMS FOR ENHANCED OIL RECOVERY IN CARBONATE RESERVOIRS

Recovering residual oil reserves and reducing the level of water cut in produced wells at minimal cost are urgent tasks for mature fields. In such conditions, the use of tertiary methods of reservoir stimulation is relevant, among which a significant share is occupied by chemical methods of enhanced oil recovery. The principle of using flow diverting technologies is to supply small rims of chemical reagents to the reservoir through the reservoir pressure maintenance system, aimed at reducing the permeability of water-flushed zones by installing a waterinsulating barrier in them and redirecting water filtration flows to reservoir zones that were not previously covered by flooding.
 In this paper, we consider the possibility of using the technology of water-swellable preformed particle polymer systems as flow-diverting reagents to increase oil recovery from reservoirs with complicated geological and physical conditions that limit the use of many reagents used in EOR.
 On the example of a reagent sample, which is a pre-crosslinked acrylamide polymer, which contains particles of clay powder (up to 40% wt.), The paper shows the results of laboratory study and experience in applying the technology based on the preformed particle polymer systems at one of the objects of the Ural-Volga region, the reservoirs of which are presented carbonate rocks. The filtration experiment showed that the injection of the preformed particle polymer systems leads to a significant redistribution of fluid flows from a more highly permeable model to a less permeable one. As a result of the research, the main features of the applicability of technology based on the preformed particle polymer systems have been identified. The analysis of the conducted field work was carried out by determining the change in the injectivity profile of the treated injection wells and estimating the additionally produced oil from the reacting production wells. Based on the results of the analysis, additional laboratory studies were carried out, on the basis of which ways were proposed to increase the efficiency of injection well treatments with preformed particle polymer systems.

SPECTRAL AND PHOTOPHYSICAL CHARACTERISTICS OF ASYMMETRIC POLYMETHINE DYES IN POLYURETHANE MATRICES

Here the composite polymer sorbent hydrogels were synthesized by in situ technique via free radical polymerization of acrylamide (AAm), 2-hydroxyethyl methacrylate (2HEMA) and N,N’-methylene-bis(acrylamide) crosslinker mixture in the presence of as-prepared dispersion of nickel-aluminum layered double hydroxide (NiAl-LDH). A content of active NiAl-LDH filler in the polymer matrix was varied in a range of 30 – 70 wt.%. It was found a high filler content suppresses a molecular mobility of copolymer matrix chains and reduces a beginning of glass transition temperature of the polymer constituent. The results of thermal analysis of polymer composites demonstrate a high hydrophilicity level of polymer matrix and high solvation energy of polar functionalities by Н2О molecules that was concluded from slow moisture elimination process while the temperature grows up to 200–210 оС. Additionally, a dehydration process and changes in a structure of thermally labile filler were also observed at the same temperature interval. At higher temperatures a thermal degradation of polymer poly(AAm-co-2HEMA) matrix is carried out. When a temperature overcomes 400 оС the partially changed filler demonstrates a chemical interaction with degraded organic constituents of the composites and defined catalytic activity as well. Studying sorption activity of the composites shown that introducing NiAl-LDH into hydrophilic polymer matrix provides anion-exchange activity to the composite sorbents and, correspondingly, the ability to eliminate the anionic contaminants from aqueous media while the polymer matrix doesn’t absorb these substances at such conditions. The highest sorption capacity of 11,40 μmol/g against model contaminant – methyl orange dye was determined for composite sorbent with filler content of 70 wt. %. At the same time sorption capacity of NiAl-LDH filler in composite sorbents reduces from 25,7 to 16,6 μmol/g while a filler content grows from 30 to 70 wt.% as a result of filler particles aggregation processes during composites formation stage. To evaluate the ability of the composite sorbents to reuse the experiment of materials recycling was performed. It was stated out the using of anion-exchange technique and aqueous Na2CO3 solution as an efficient and non-hazardous eluent provides 80 % recovering efficiency of the active filler in the composites. It can be concluded the composite sorbents demonstrate a high overall efficiency and are valuable materials for practical application for decontamination of waste water.

Robust cement composite with low hydration temperature and high mechanical performance achieved by Field's metal and acrylic acid-acrylamide copolymer

Concrete as an artificial stone owns the weakness of high brittleness and poor flexural strength, dramatically restricting its potential. Therefore, it is crucial to reduce the brittleness and increase the flexural strength of concrete to prolong its service life. Herein, we developed a cement composite with low hydration temperature and high mechanical strength (especially in flexural strength) by combining Field’s metal with in situ polymerization of acrylic acid (AA) and acrylamide (AM). A cement composite with compressive and flexural strength increased by 8.2% and 174.2% was achieved by tuning the dosage of Field's metal and AA-AM copolymer. The hydration temperature was significantly reduced with the assistance of Field’s metal and AA-AM copolymer, inhibiting the formation of the thermal crack. In situ polymerization of AA and AM monomers was responsible for improving the intrinsic toughness of cement hydrates by constructing a polymer-cement network, significantly enhancing flexural strength. The in situ polymerized AA-AM copolymer acted as a bridge between Field’s metal and the cement matrix, improving their interface and contributing to the increased mechanical strength. The filling effect of Field’s metal and AA-AM copolymer refined the pore structure of the composite as well. Overall, our findings may offer a promising strategy for developing more robust, resilient, and sustainable cementitious materials.

Highly dispersed nanocomposites based on polymer/inorganic hybrids and nickel nanoparticles: the role of the matrix structure in the process of in situ formation

A series of polymer/inorganic hybrids based on silica sol and polyacrylamide (SiO2-g-PAAm) with different number and length of PAAm chains was obtained by radical graft polymerization of acrylamide from the surface of SiO2. The main molecular and structural parameters of the hybrids, such as the chemical composition, average radius and charge of SiO2 particles, the number of grafts per one particle and their molecular weight, the average diameter and hydrodynamic volume of hybrid particles, and the thickness of the PAA layer, were determined. For this, elemental analysis, DTGA, static light scattering, viscometry, potentiometric titration, and TEM were used. The functional properties of hybrids as hydrophilic matrices in the in situ synthesis of nickel nanoparticles by borohydride reduction of metal ions from the Ni(NO3)2·6H20 salt in an aqueous medium have been studied. Using the method of UV-Vis spectroscopy and the developed original approach, the kinetics and efficiency of the formation of NiNPs in hybrid solutions were characterized, depending on the structure and concentration of the hybrid matrices and the concentration of the metal salt. An increase in the rate of accumulation and yield of NiNPs in solutions of all hybrids was found with an increase in salt concentration in the range of 0,010-0,078 kg·m-3, as well as a predominant decrease in the reaction rate with an increase in the concentration of hybrid matrices from 0,5 to 2,0 kg·m-3. It was shown that the structure of the hybrid matrices, determined by the number and length of PAAm chains, as well as the permeability of the grafted polymer layer, was one of the key factors affecting the formation rate and yield of NiNPs. It provided greater or lesser accessibility of the active groups of the "corona" and the inorganic "core" for metal ions and reducing agent molecules. Morphological studies of purified reduction products were carried out by TEM. Based on them, the main structural elements of highly dispersed NiNPs/SiO2-g-PAAm nanocomposites were established – swollen hairy particles of hybrids with small amorphous NiNPs (1,7±0,8 nm) included in the polymer "corona".

A Liquid Metal Microdroplets Initialized Hemicellulose Composite for 3D Printing Anode Host in Zn-Ion Battery.

Maintaining a steady affinity between gallium-based liquid metals (LM) and polymer binders, particularly under continuous mechanical deformation, such as extrusion-based 3D printing or plating/stripping of Zinc ion (Zn2+ ), is very challenging. Here, an LM-initialized polyacrylamide-hemicellulose/EGaIn microdroplets hydrogel is used as a multifunctional ink to 3D-print self-standing scaffolds and anode hosts for Zn-ion batteries. The LM microdroplets initiate acrylamide polymerization without additional initiators and cross-linkers, forming a double-covalent hydrogen-bonded network. The hydrogel acts as a framework for stress dissipation, enabling recovery from structural damage due to the cyclic plating/stripping of Zn2+ . The LM-microdroplet-initialized polymerization with hemicellulosescan facilitate the production of 3D printable inks for energy storage devices.

Efficient Photocatalytic Degradation of Methylene Blue Dye from Aqueous Solution with Cerium Oxide Nanoparticles and Graphene Oxide-Doped Polyacrylamide.

A cerium oxide nanoparticles (CeO2-NPs)/graphene oxide (GO)/polyacrylamide (PAM) ternary composite was synthesized through free-radical polymerization of acrylamide in the presence of CeO2 nanoparticles and GO in an aqueous system. The synthesized composite material was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy techniques and applied for the photocatalytic degradation of methylene blue (MB) dye from an aqueous solution. Tauc's model for direct transition was used to model for the optical band gap. The key operating parameters such as the amounts of CeO2-NPs and GO, pH, initial MB concentration, type of light irradiation, and contact time have been optimized to achieve the highest MB degradation percentage. The photocatalysis process was pH-dependent, and the optimum pH value was found to be 12.0. Under UV-A light, 90% dye degradation occurred in 90 min. The degradation of MB was also specified in terms of total organic carbon (TOC) and chemical oxygen demand (COD). Free-radical capture experiments were also performed to determine the role of radical species during the photocatalytic oxidation process. The photocatalytic process showed that the equilibrium data is in good agreement with the Langmuir-Hinshelwood kinetic model. A rate constant of 0.0259 min-1 was obtained. The hydrogel was also tested to assess its reusability, which is an important key factor in practical wastewater treatment. The photocatalytic activity only decreased to 75% after nine uses.

Salt Ion Diffusion Behavior and Adsorption Characteristics of Fracturing Fluid in Tight Sandstone Gas Reservoir

The degree of salinity in the hydraulic fracturing rejection fluid of the Shaximiao reservoir in the central Sichuan Basin is high, and the underlying mechanism causing this salinity is not clearly understood. We evaluated the rock structure of tight sandstone, including rock composition, pore structure, ion diffusion, and adsorption behavior, to determine how the rock structure influences the mechanism of the sandstone’s interaction with the fracturing fluid. X-ray diffraction revealed that the rock mineral fraction has a significant clay mineral concentration. The results of linear swelling experiments revealed that the water sensitivity of tight sandstone reservoirs exhibits moderately robust characteristics. The time required for salt ion diffusion stabilization is much longer than that required for self-imbibition stabilization, and the diffusion of salt ions is almost log-linear with time after imbibition stabilization. The diffusion rates of salt ions were determined for different single minerals and particle sizes, with clay minerals and particle sizes controlling the diffusion rates. The samples were treated with different concentrations of KCl and acrylamide polymer solutions, and both the pore size distribution and pore throat properties were characterized by low-temperature nitrogen adsorption. Although the adsorption isotherms of both KCl and polymers are consistent with the Langmuir model, their adsorption mechanisms acting on tight sandstone and the effect of adsorption on the pore throat structure are inconsistent. The adsorption of potassium chloride enhances the rock’s pore throat diameter and permeability by increasing the uniformity of the pore throat by electrostatic adsorption with clay particles. However, polymer adsorption reduces the pore diameter of the rock and forms a thin film that obstructs the pore throat, complicating the pore throat and weakening its permeability. This research has led to a greater comprehension of the ion diffusion characteristics of the tight sandstone in the Shaximiao reservoir and the adsorption mechanism on the pore structure of the rock.

Hydrophobically Associating Polyacrylamide “Water-in-Water” Emulsion Prepared by Aqueous Dispersion Polymerization: Synthesis, Characterization and Rheological Behavior

The hydrophobically associating polyacrylamide (HAPAM) is an important kind of water-soluble polymer, which is widely used as a rheology modifier in many fields. However, HAPAM products prepared in a traditional method show disadvantages including poor water solubility and the need for hydrocarbon solvents and appropriate surfactants, which lead to environmental pollution and increased costs. To solve these problems, we reported a novel kind of HAPAM "water-in-water" (w/w) emulsion and its solution properties. In this work, a series of cationic hydrophobic monomers with different alkyl chain lengths were synthesized and characterized. Then, HAPAM w/w emulsions were prepared by the aqueous dispersion polymerization of acrylamide, 2-methylacryloylxyethyl trimethyl ammonium chloride and a hydrophobic monomer. All these emulsions can be stored more than 6 months, showing excellent stability. An optical microscopy observation showed that the particle morphology and the particle size of the HAPAM emulsion were more regular and bigger than the emulsion without the hydrophobic monomer. The solubility tests showed that such HAPAM w/w emulsions have excellent solubility, which took no more than 180 s to dilute and achieve a homogeneous and clear solution. The rheology measurements showed that the HAPAM association increases with a hydrophobe concentration or the length of hydrophobic alkyl chains, resulting in better shear and temperature resistances. The total reduced viscosity was 124.42 mPa·s for cw101, 69.81 mPa·s for cw6-1, 55.38 mPa·s for cw8-0.25, 48.95 mPa·s for cw12-0.25 and 28 mPa·s for cw16-0.25 when the temperature increased from 30 °C to 90 °C. The cw8-2.0 that contains a 2 mol% hydrophobe monomer has the lowest value at 19.12 mPa·s due to the best association. Based on the excellent stability, solubility and rheological properties, we believe that these HAPAM w/w emulsions could find widespread applications.

Rapid RAFT Polymerization of Acrylamide with High Conversion.

Rapid RAFT polymerization can significantly improve production efficiency of PAM with designed molecular structure. This study shows that ideal Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization of acrylamide is achieved in dimethyl sulfoxide (DMSO) solution at 70 °C. The key to success is the appropriate choice of both a suitable RAFT chain transfer agent (CTA) and initiating species. It is illustrated that dodecyl trithiodimethyl propionic acid (DMPA) is a suitable trithiocarbonate RAFT CTA and is synthesized more easily than other CTAs. Compared to other RAFT processes of polymers, the reaction system shortens reaction time, enhances conversion, and bears all the characteristics of a controlled radical polymerization. The calculation result shows that high concentrations can reduce high conversions, accelerate the reaction rate, and widen molecular weight distributions slightly. This work proposes an excellent approach for rapid synthesis of PAMs with a restricted molecular weight distribution.

Tensile properties of sulfoaluminate cement-based grouting materials toughened by in-situ polymerization of acrylamide

Polymer-modified cementitious materials with high compression and tensile resistance are considered the most promising materials for fracture grouting in underground projects. In this paper, polyacrylamide was prepared by in-situ polymerization of acrylamide, and its toughening effect on sulfoaluminate cement-based grouting material (SCGM) was investigated. The results show that the toughness index of the acrylamide modified SCGM (PAM-SCGM) was 57.55 times higher than that of the plain one. The PAM-SCGM three-stage failure model and the PAM-AFt-CS dual network structure model were proposed and validated by SEM. A model of PAM inhibition of hydration was proposed and validated using heat of hydration, FT-IR and XRD. BET was used to reveal the evolution of the pore structure and validated the tensile model. An empirical formulation of a three-stage mechanical model was proposed and regressed to validate it. The four models and an empirical formulation showed the great potential for engineering applications.

Energy saving technology of acrylamide polymerization in plate reactor based on phase change heat transfer

A new type of plate heat exchanger reactor was designed and studied to transfer the heat of acrylamide polymerization by using phase change heat transfer materials to improve the product performance and alleviate the phenomenon of polymer cross-linking and molecular weight reduction caused by high temperature of acrylamide polymerization. The results showed that the key factor limiting the heat transfer was the thickness of polyacrylamide colloid. Reducing the heat transfer distance could effectively accelerate the heat transfer of polyacrylamide colloid. The paraffin wax has good thermophysical properties and stability. It could maintain a constant temperature in the phase change process during the polymerization. Different monomer concentration acrylamide polymerization process found that the higher the monomer concentration, the better the heat transfer effect, the system temperature change range is reduced to achieve the polymerization process temperature control, reduce energy consumption, energy saving and environmental protection development. Compared with the traditional aqueous solution polymerization process without phase transition heat under the same conditions, the molecular weight of the polyacrylamide polymerization process based on phase transition heat increased by 38.5%. The main mode of heat transfer between the polyacrylamide colloid and the phase change material was determined by numerical calculations as heat conduction.

Fabrication of photochromic and electrochromic (PVP-am)/WO3/MoO3 hydrogel composites and glass films with programmable shapes

Recently, the fabrication of functional and stimuli-responsive hydrogels using deep eutectic solvent derivatives is gaining tremendous scientific recognition owing to their unique self-switching properties. In this study, perfluorinated deep eutectic mixtures were prepared as the template for the synthesis of WO3/MoO3 composites. The metal oxide-based composites were further employed as a chemical crosslinking agent for the polymerization of polyvinyl pyrrolidine (PVP) and acrylamide (Am), for the construction of (PVP-Am)/WO3/MoO3 hydrogel composites. The hydrogels displayed unique morphologies and mechanical properties. The hydrophilic nature of hydrogels as well as the high concentration of dispersed WO3/MoO3 composites in the polymer network contributes to their photochromic activity and allows an immediate coloration upon exposure to light at a short time. Howbeit, the low concentration of the dispersed WO3/MoO3 composites in the dry glass membrane is responsible for the blue coloration and an extended time of photochromic response. In addition, the electrochromic behavior of the hydrogel composites displayed a strong quasi-rectangular shape potential window as well as a well-defined redox cyclic voltammetry curve when exposed to high voltage. This could be due to the photoredox property of the WO3/MoO3 composites responsible for charge transfer between the different oxidation states.

Self-adhesive, self-healing, biocompatible and conductive polyacrylamide nanocomposite hydrogels for reliable strain and pressure sensors

To realize long-term and stable applications of wearable and flexible sensors for motion detection, health analysis and wisdom medication in harsh environments, self-healing, self-adhesive, electrically conductive and biocompatible polyacrylamide (PAM) nanocomposite hydrogels are fabricated as flexible strain or pressure sensors by in situ polymerization of acrylamide in the presence of polydopamine-modified carbon nanotubes (PDA@CNTs) for effectively detecting human motions, identifying materials and their shapes, and transmitting health information. The resultant PDA@CNT/PAM nanocomposite hydrogel exhibits a high self-healing efficiency of 97.3%, excellent biocompatibility, and strong adhesion with substrates based on hydrogen bonding and π–π stacking interactions. Based on the piezoresistive effect, the nanocomposite hydrogel-based strain sensor exhibits a high sense gauge factor of 3.93 at a strain of 400% and responds quickly with a fast response time of 76 ms when detecting human movement. Thanks to the contact electrification and the electrostatic induction, the nanocomposite hydrogel-based pressure sensor can respond to pressure linearly and generate voltage signals in the absence of an additional power supply. Furthermore, the self-powered smart ring made of the silicone rubber-coated PDA@CNT/PAM hydrogel enables efficient and concise information transmission via Morse code.

Sol-gel fabrication of porous ceria microspheres for thermochemical carbon dioxide (CO2) splitting

Porous CeO2 has been of great interest recently, due to its great catalytic efficiency in splitting CO2 into CO and O2. Porous CeO2 microspheres are the key to scaling up such reactions in the fluidized-bed solar thermochemical reactors. In this paper, we report the processing and CO2 splitting performance of porous ceria microspheres. To fabricate the porous ceria microspheres, homogenous cerium-based sol-gel precursors were synthesized from cerium acetate. The acrylamide (AM) was used as both solidification and pore-generation agent. The polymerization of acrylamide facilitated the conversion of liquid droplets to solid gel microspheres. The optimal AM content was around 20 wt%, ensuring both sufficient porosity and the integrity of the ceria microspheres after thermal decomposition. After heat treatment at 1500 °C for 1 h, porous CeO2 microspheres were obtained, with an average diameter of ∼800 μm and surface area of 2.9 m2/g. These microspheres had high porosity and good sphericity. The CO2 splitting performances of these microspheres were characterized using thermogravimetric analysis (TGA). During the thermal cycles between 1000 and 1400 °C, the O2 yield of porous ceria microspheres was 49 μmol/g, and the CO yield was 88 μmol/g. Compared with porous ceria granules of particle size of ∼800 μm, the porous ceria microspheres exhibited higher O2 and CO production yields. After thermochemical cycles, the microspheres were not sintered together, and the surface area was slightly reduced to 2.7 m2/g.

Temperature effects on axial dispersion in a photopolymer-based holographic lens.

This study aims to discover whether temperature has an effect on axial dispersion in a photopolymer-based holographic lens. A typical coaxial holographic lens is recorded in the acrylamide polymer system. The axial dispersion spectrum is read and collected by using a supercontinuum source and spectrometer. The temperature effects on axial dispersion in a photopolymer-based holographic lens are investigated experimentally. With increasing temperature from 23°C to 70°C, the diffraction spectrum shifts, and the axial dispersion is shortened evidently. The peak wavelength of the dispersion spectrum shifts from 629.05 to 612.50nm with an obvious blueshift of 16.55nm. The spatial position of the peak wavelength also decreases from around 40 to 22mm from the material surface. Simultaneously, the position sensitivity of the device reduces from 2.53 to 1.50nm/mm. The shortening of the effective focal length and reduction of the diffraction intensity indicate that the high temperature above 40°C is a disadvantageous factor for actual use of a holographic lens-based spectral confocal measuring device. In practical application, a constant temperature is a significant means to ensure the measurement accuracy and range.

Polyacrylamide/EDTA-modified chitosan/graphene oxide hydrogels as an adsorbent and supercapacitor for sustainable applications

Due to high security and versatility, hydrogels have attracted great interest in sustainable applications such as wastewater treatment and energy storage. However, the poor adsorption capacity as an adsorbent and the low conductivity as an electrolyte seriously restrict the sustainable application of hydrogels. Here, we prepare nanocomposite hydrogels (PAAm/CS-EDTA/GO) by mixing ethylene diamine tetraacetic acid (EDTA)-modified chitosan (CS) and graphene oxide (GO) in crosslinking polymerization of acrylamide (AAm). Nanocomposite gives PAAm/CS-EDTA/GO hydrogel excellent mechanical properties (e.g., fracture energy of ∼1208 kJ∙m−3). EDTA, CS and GO support rich and special adsorption sites for the removal of metal ions and dyes. The addition of lithium chloride (LiCl) makes PAAm/CS-EDTA/GO/Li hydrogel have anti-freezing and anti-dehydration properties. Interestingly, the synergy of CS-EDTA and GO increases the conductivity of the hydrogel. The supercapacitor assembled by PAAm/CS-EDTA/GO/Li hydrogel electrolyte shows high capacitance and temperature tolerance. Our work provides a route for the rational development of adsorption materials and energy storage devices for sustainable applications.