High Polymer Research Articles

High‐Pressure Fabrication of Binary Organic Solar Cells with High Molecular Weight D18 Yields Record 19.65 % Efficiency

AbstractIn this work, inspired by the principles of a pressure cooker, we utilized a high‐pressure method to address the processing challenges associated with high molecular weight polymers. Through this approach, we successfully dissolved high molecular weight D18 in chloroform at 100 °C within a pressure‐tight vial. The increased steam pressure raised the boiling point and dissolving capacity of chloroform, enabling the creation of a hybrid film with superior properties, including more ordered molecular arrangement, increased crystallinity, extended exciton diffusion length, and improved phase morphology. Organic solar cells (OSCs) based on D18 : L8‐BO prepared using this high‐pressure method achieved an outstanding power conversion efficiency of 19.65 %, setting a new record for binary devices to date. Furthermore, this high‐pressure method was successfully applied to fabricate OSCs based on other common systems, leading to significant enhancements in device performance. In summary, this research introduces a universal method for processing high molecular weight D18 materials, ultimately resulting in the highest performance reported for binary organic solar cells.

The role of the solvent nature in stretching polymer solutions (polyacrylonitrile spinning using different solvents)

We investigated how different solvents' affinity with polyacrylonitrile affects the formation of a jet that leads to stable fiber spinning. The study focused on two concentrations, one near and one above the crossover point where the topological entanglements are formed in the semi-dilute solutions. The role of the physical parameters of the solutions, including solvent-polymer affinity, viscosity, surface tension, and relaxation times, was analyzed. The experiment involved the uniaxial deformation of a solution drop under its weight, observed using a high-speed microscopic camera. The stability of the jet was associated with the relaxation time and solvent-polymer affinity. The continuous fiber spinning is mainly determined by the high enough polymer concentration in the solution, and the solvent nature, or by how the solution state is close to the theta conditions. Bicomponent mixed solvents offer two viable routes to achieve this – evaporating a more volatile component from the mixture to increase the polymer concentration, or modifying the solvent with a combination of solvents of different solvent quality. Both approaches have been experimentally validated, enabling the production of continuous stable fibers in the gel stretching regime. In this case, the jet stretching occurs under conditions Wi > 1. Thereby, the transition to the gel state promotes the necessary conditions for macromolecule orientation during fiber spinning.

In situ synthesis and stabilization of PVP-coated aluminum nanoparticles by one-step pulsed laser ablation in liquid: Investigation and quantification of PVP coverage effects

This study explored the use of one-step pulsed laser ablation (PLA) in liquid process for in situ synthesis of polyvinylpyrrolidone (PVP) coated highly-stabilized Al nanoparticles (NPs). The effect of different process variables such as laser energy, PVP concentration, and PVP chain length on the composition, size, distribution, and stability of the synthesized NPs was investigated. The results showed that adding PVP to the solution led to smaller average size of NPs with a more uniform distribution, and enhanced resistance to aggregation. This study also revealed that while PVP only partially inhibited the reaction between Al NPs and oxygen during NP generation, it could provide excellent blocking performance against hydroxylation to NPs in subsequent aging experiments. The concept of polymer coverage was introduced to quantify the protective effect of PVP polymers on Al NPs. At 0.1 J laser energy and a K-30 PVP concentration of 10 g/L, a polymer coverage value of 6773 was achieved, maximizing the amount of polymer per unit NP surface area. It was verified that Al NPs' reactivity was most efficiently suppressed under this condition. However, it was observed that the critical polymer coverage value required to suppress the reaction of Al NPs with their surroundings depended on process variables such as laser energy and polymer chain length. This study also confirmed that using high molecular weight polymers can further improve the anti-agglomeration performance and ablation efficiency while lowering the required critical polymer coverage value.

Preparation of high-yield carbon quantum dots and paper-based sensors from biomass wastes by mechano-chemical method

The synthesis of carbon quantum dots (CQDs) from biomass through a "bottom-up" method has attracted a great deal of interest because of its outstanding environmental and economic advantages. However, the yield of biomass-based CQDs is still low due to the high polymerization of biochar. In this study, we propose a new approach for harvesting high-yield biomass-based CQDs by integrating mechanochemistry and strong chemical oxidation. Ball milling can reduce the particle size and resistance of biochar and increase the contents of CC, while the powerful oxidant HOO- produced by alkaline hydrogen peroxide can break CC to generate biomass-based CQDs. Using this two-step process, the yields of biomass-based CQDs reached 57.75% for blue-green algae, 65.8% for straw, 47.9% for corn protein meal, and 45.35% for Typha angustifolia. Based on the excellent sensitivity and selectivity for Fe3+ of biomass-based CQDs, CQDs paper-based sensors were prepared for expedient and precise detection of Fe3+ in surface water, wastewater treatment plant effluent, and tap water. When the Fe3+ content is between 0 and 60 μM, the R2 of Fe3+ detection by blue-green algae CQDs can reach 0.9956. This work provides a new and reliable method for the large-scale preparation of biomass-based CQDs and expands their environmental applications.

Heterogeneity of Active Sites in the Polymer Chain Transfer Reactions at Olefin Polymerization over Multisite Supported Ziegler-Natta Catalysts.

In this review, we summarize and discuss our experimental data published in a number of papers on the transfer reactions of polymer chains in the polymerization of ethylene, propylene, and hexene-1, and the copolymerization of ethylene with α-olefins over multisite supported titanium-magnesium catalysts (TMC). Three groups of transfer reactions are discussed in the review: (1) transfer reactions with AlEt3 cocatalyst, (2) transfer reactions with hydrogen, and (3) transfer reactions with participation of α-olefins in the case of ethylene copolymerization with α-olefins. We have found polymerization conditions where it is possible to observe heterogeneity of active sites of TMC for all three groups of the indicated reactions. It is shown that (1) the transfer reaction with AlEt3 proceeds with higher reactivity on the active sites that produce polymers with low molecular weight; (2) the transfer reaction with hydrogen, in the case of α-olefin polymerization and copolymerization of ethylene with α-olefins, proceeds with higher reactivity on the active sites which produce polymers with high molecular weight; (3) the transfer reaction with α-olefins proceed with higher reactivity on the active sites that produce high molecular weight polymers.

Estimating Gas Sorption In Polymeric Membranes From The Molecular Structure: A Machine Learning Based Group Contribution Method For The Non-Equilibrium Lattice Fluid Model (ML-GC-NELF)

Since its inception, the non-equilibrium lattice fluid (NELF) model has become a vital tool in correlating and predicting the gas solubility behaviour in glassy polymeric membranes. But like its equilibrium variant, the NELF model is highly constrained by the availability of the pure polymer characteristic parameters, which are not always convenient to obtain as the need arises. In this study, we provide a proof-of-concept for building a machine learning-based group contribution method (ML-GC) for the Sanchez–Lacombe equation of state (EoS) pure polymer parameters. The ML-GC model was built using a modified version of the Marrero and Gani’s method, which incorporates machine learning regression into the GC parameterisation process. The final model was capable of reproducing the parameters of a randomly selected test set of polymers, with a diverse range of chemical structures. The resultant average AARD% of the predicted densities in this set is 5.59%, with no polymer exceeding 15%. Moreover, to test the model’s capabilities in estimating the parameters of high glass transition temperature polymers, we predicted a priori the characteristic parameters of 6 polyimides from the knowledge of their molecular structure. The ML-GC parameters were also incorporated into the NELF model to predict the infinite dilution solubility coefficients (S0) of some of these polymers and the results were validated against experimental data. Furthermore, the ML-GC-NELF model was also used for the first time to represent effectively the gas solubility isotherms in PIM-PI-SBI and PIM-PI-EA with relatively small magnitudes of the binary interaction parameters (kij). Despite the small data-set used herein, the model performance was satisfactory, however, as more data are being published in literature, the proposed ML-GC model has the potential of providing even more accurate predictions for a wider range of polymers, ultimately leading to lesser reliance on experimental data for modelling the gas sorption.

Metal-catalyzed copolymerizations of epoxides and carbon disulfide for high-refractive index low absorbance adhesives and plastics.

High-refractive index plastics are useful materials due to their optical properties, ease of processing, and low-costs compared to their inorganic counterparts. Catalytic carbon disulfide (CS2) copolymerization with epoxides is one method for producing low-cost high refractive index polymers. The reaction is accompanied by an oxygen-sulfur exchange reaction which produces irregular microstructures in the repeating units. In this study, metal salen catalysts were investigated with different metal centers (Al, Cr, Co) and salen ligand electronics, sterics, backbones, and co-catalyst in the copolymerization of CS2 with propylene oxide (PO) and cyclohexene oxide (CHO). The results reveal the essential nature of Cr metal centers on reactivity and the backbone geometry on monomer selectivity. There were no significant impacts on the O-S exchange reaction when ligand design changed, however PO and CHO/CS2 copolymers yield different monothiocarbonate microstructures. Additionally, the effects of microstructure on optical and thermal properties were investigated using spectroscopic ellipsometry and calorimetry, respectively. The CHO system produced high T g plastics (93°C) with high refractive indexes (n up to 1.64), modest absorbance (κ < 0.020), and Abbe numbers of 32.2 while PO yielded low T g adhesives (T g = 9°C) with high refractive indexes (n up to 1.73), low absorbance (κ < 0.005), and low Abbe numbers (V D = 19.1).

High−molecular weight poly(2-substituted 1,3-diene)s using iminopyridine iron precatalysts at high polymerization temperature and low iron loading

The synthesis of a series of iron(II) dichloride complexes bearing iminopyridine (ImPy) ligands, differing in the substituents at the pyridine, bridging carbon and N−aryl ring is described (1-LHPh−7-LHS). The X-ray structures of some of them are presented. All the iron compounds and, for comparison, the already reported 8-LHPhP, that features bulky ortho isopropyl N−aryl substituents, have been investigated as precatalysts for the polymerization of 2-substituted 1,3-dienes, i.e., isoprene and β-myrcene, using a low excess of methylaluminoxane (MAO) as alkylating reagent, iron loading as low as 0.025 mol% and variable temperature up to 100 °C. The goal is to have insights into ligand effects on catalyst reactivity and selectivity and to recognize the most robust iron precatalysts to access high-molecular weight (MW) polymers using low iron loading and high polymerization temperature, which meets current demands of mild, operationally simple approach. Particularly, the ketimine 4-LMePh and 5-LPhPh are more stable and least prone to chain termination than all the aldimine parents. 4-LMePh and 5-LPhPh produce cis-1,4/3,4 ultra-high-MW poly(isoprene)s and solid high-MW poly(β-myrcene)s, while maintaining narrow and unimodal molecular weight distribution. In this study we intentionally kept the monomer conversion low to provide a valuable assessment of catalyst stability, uncorrupted by mass or heat transport limitations. Furthermore, the synthesis of the unsubstituted aminopyridine (AmPy) iron(II) dichloride complex 9-LAPh, analogue to 1-LHPh, is described. 9-LAPh has been demonstrated to be a valuable probe for stability studies. Given the variety of catalytic transformations and substrates for which (ImPy)FeCl2 precatalysts have promising reactivity and selectivity, those developed in this study offer promising applications also beyond the polymerization of 1,3-dienes.

Continuous generation of cross-linked polymer nanoparticles employing an ultrasonic microreactor

In this article, a new system employing an ultrasonic microreactor coupled with a tubular reactor is presented for the continuous generation of polymer nanoparticles. The continuous generation of cross-linked polymer nanoparticles utilizing the monomer butyl methacrylate and the cross-linker ethylene glycol dimethacrylate is demonstrated. Firstly, the miniemulsion polymerization of a monomer-in-water miniemulsion is studied in a batch system. Secondly, a coiled tubular reactor is employed for the continuous polymerization of the miniemulsion generated by an ultrasonic microreactor. Finally, the influence of monomer volume fraction and surfactant concentration on the synthesized polymer nanoparticles is studied. Polymer particles in a size range of 50–250 nm are synthesized and a high polymerization conversion is achieved utilizing the system demonstrated in this article.

Fast photobleachable and low migration one-component green indole visible photoinitiators

Six symmetric D-π-A-π-D indole derivatives (IDs) have been investigated as visible light photoinitiators (PIs). The IDs, with different indole as the electron donor (D), C = C bond as the π-bridge and carbonyl group as the electron acceptor (A), are type II PIs owning to their intermolecular hydrogen abstraction. In the process of generating free radicals, the carbonyl transformed to hydroxyl alkyl radicals, which disrupted the large conjugation systems and resulted in the color fading. Real time infrared (RT-IR) indicated that IDs and ID/N-methyldiethanolamine (MDEA) effectively initiated the photopolymerization of 1, 6-hexanediol diacrylate under illumination. ID-HA containing acrylate double bonds is expected to be served as not only a PI but also a crosslinker with extremely high migration stability. The extraction rate of ID-HA from the polymer films following 30 min of illumination was 1.0 %. ID-HA has a lower energy in the excited triplet state (DFT calculations), which is favorable for electron transfer and radical generation. Therefore, the color of ID-HA in acetonitrile solution completely faded within 15 s under illumination, demonstrating the best photobleaching behavior. Meanwhile, the polymerization conversion initiated by it alone could reach as high as 81 %. Furthermore, 47 mm high (with 96.8 % whiteness bleaching ratio) and 55 mm high (with 94.5 % whiteness bleaching ratio) polymer columns were obtained respectively, by using ID-HA and ID-HA/MDEA as PI. Thus, their outstanding photobleaching performance, migration stability and thermal stability endow IDs potential applications in deep photopolymerization, food packaging and biomedicine.

Energy Storage Performance of Polymer-Based Dielectric Composites with Two-Dimensional Fillers.

Dielectric capacitors have garnered significant attention in recent decades for their wide range of uses in contemporary electronic and electrical power systems. The integration of a high breakdown field polymer matrix with various types of fillers in dielectric polymer nanocomposites has attracted significant attention from both academic and commercial sectors. The energy storage performance is influenced by various essential factors, such as the choice of the polymer matrix, the filler type, the filler morphologies, the interfacial engineering, and the composite structure. However, their application is limited by their large amount of filler content, low energy densities, and low-temperature tolerance. Very recently, the utilization of two-dimensional (2D) materials has become prevalent across several disciplines due to their exceptional thermal, electrical, and mechanical characteristics. Compared with zero-dimensional (0D) and one-dimensional (1D) fillers, two-dimensional fillers are more effective in enhancing the dielectric and energy storage properties of polymer-based composites. The present review provides a comprehensive overview of 2D filler-based composites, encompassing a wide range of materials such as ceramics, metal oxides, carbon compounds, MXenes, clays, boron nitride, and others. In a general sense, the incorporation of 2D fillers into polymer nanocomposite dielectrics can result in a significant enhancement in the energy storage capability, even at low filler concentrations. The current challenges and future perspectives are also discussed.

Simulating study of cochlear sensors based on PVDF organic polymer materials

Cochlear implant is an effective choice to recover hearing for patients with sensorineural deafness. With the development of society, people’s demand for cochlear implants in all aspects is increasing. Polyvinylidene fluoride (PVDF) film is a kind of high polymer with excellent properties, which has broad application prospects in the field of cochlear implant. This article uses COMSOL software to simulate PVDF films and explore the size effect on the sensor performance. The simulation results show that the eigenfrequency is linearly related to height, meanwhile the vibration mode and electric potential also vary with height. The cochlear sensor is simulated in the range of human ear-sensitive hearing frequency, and the cochlear sensor has excellent piezoelectric properties. The cochlear sensor obtained after simulation can help patients with sensorineural deafness to better identify their hearing.

Porous scaffold hydroxyapatite from sand lobster shells (Panulirus homarus) using polyethylene oxide/chitosan as polymeric porogen for bone tissue engineering.

The hydroxyapatite (HAp; Ca10 (PO4 )6 (OH)2 )) has good biocompatibility, bioactivity, and osteoconductivity as a bone implant because the main inorganic mineral of human bone is HAp. The use of scaffold HAp from biogenic resources that contain high calcium and polymer as a pore forming agent to support bone growth is a longstanding area of interest. In this study, porous scaffolds based on HAp were synthesized from sand lobster (SL; Panulirus homarus) shells as a source of calcium using the porogen leaching method with polyethylene oxide (PEO) and chitosan (Chs) as polymeric porogen. The present study aims to synthesize HAp derived from SL shells and evaluate the effect variations of PEO on the physicochemical properties of the scaffold and cytotoxicity in cell viability assay. Briefly, the SL shell powder was calcinated with temperature variations of 600°C, 800°C, and 1000°C for 6 h. Based on the characterization, it was shown that 1000°C was the optimum calcination temperature for SL shells to synthesize HAp using the precipitation method. The characterization results of HAp using energy dispersive x-ray (EDX) revealed that the molar ratio of Ca/P was 1.67. The Fourier transform infrared (FTIR) and x-ray diffractometer (XRD)spectral patterns indicated that HAp had been successfully synthesized with minor β-tricalcium phosphate (β-TCP), a calcium phosphate with high biocompatibility. Porous scaffolds were synthesized by varying the concentration of PEO at 0, 5, 10, and 15 wt %. Physicochemical analysis revealed that a higher concentration of PEO affected decreased crystallinity and compressive strength, but on the other hand, the porosity and pore sizes increased. Based on the physicochemical analysis, the synthesized porous scaffold showed that HAp/PEO/Chs 15 wt % had the most potential as a scaffold for biomedical applications. MTT Assay, after 24 h incubation, revealed that the scaffold was safe for use at low concentrations on the MC3T3E1 osteoblast cells, with a percentage of cell viability of 83.23 ± 3.18% at 23.4375 μg/mL. Although the cell viability decreased at higher concentrations, the HAp/PEO/Chs 15 wt % scaffold was cytocompatible with the cells. Thus, in the present study, HAp/PEO/Chs 15 wt % was the best scaffold based on pore structure, chemical composition, mechanical and crystalographic properties and cell viability.

Visible Light Photoiniferter Polymerization for Dispersity Control in High Molecular Weight Polymers.

The synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible-light controlled photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization is reported here to realize this goal. Key to this strategy is the use of switchable RAFT agents (SRAs) to tune polymerization activities coupled with the inherent highly living nature of photoiniferter RAFT polymerization. The polymerization activities of SRAs were in situ adjusted by the addition of acid. In addition to a switchable chain-transfer coefficient, photolysis and polymerization kinetic studies revealed that neutral and protonated SRAs showed different photolysis and polymerization rates, which is unique to photoiniferter RAFT polymerization in terms of dispersity control. This strategy features no catalyst, no exogenous radical source, temporal regulation by visible light, and tunable dispersities in the unprecedented high molecular weight regime (up to 500 kg mol-1 ). Pentablock copolymers with three different dispersity combinations were also synthesized, highlighting that the highly living nature was maintained even for blocks with large dispersities. Tg was lowered for high-dispersity polymers of similar MWs due to the existence of more low-MW polymers. This strategy holds great potential for the synthesis of advanced materials with controlled molecular weight, dispersity and sequence.

Melt Electrowriting of Nylon-12 Microfibers with an Open-Source 3D Printer.

This study demonstrates how either a heated flat or cylindrical collector enables defect-free melt electrowriting (MEW) of complex geometries from high melting temperature polymers. The open-source "MEWron" printer uses nylon-12 filament and combined with a heated flat or cylindrical collector, produces well-defined fibers with diameters ranging from 33±4 to 95±3µm. Processing parameters for stable jet formation and minimal defects based on COMSOL thermal modeling for hardware design are optimized. The balance of processing temperature and collector temperature is achieved to achieve auxetic patterns, while showing that annealing nylon-12 tubes significantly alters their mechanical properties. The samples exhibit varied pore sizes and wall thicknesses influenced by jet dynamics and fiber bridging. Tensile testing shows nylon-12 tubes are notably stronger than poly(ε-caprolactone) ones and while annealing has limited impact on tensile strength, yield, and elastic modulus, it dramatically reduces elongation. The equipment described and material used broadens MEW applications for high melting point polymers and highlights the importance of cooling dynamics for reproducible samples.

Pea protein globulins: Does their relative ratio matter?

The relatively low abundance of 11S legumin in pea protein, coupled with the wide diversity in 7S vicilin to 11S legumin ratio among pea protein ingredients, are assumed contributors to inferior and inconsistent properties relative to soy protein. To improve the performance of pea protein ingredients in food applications, optimum protein profile must be identified. Therefore, this work followed a holistic approach to determine the impact of 7S/11S ratio on pea protein structure, functionality, and nutritional quality. Vicilin- and legumin-rich fractions were isolated and combined in different proportions to produce samples of varying 7S/11S ratios. For the first time, pea protein isolate was also enriched with 11S legumin to evaluate the impact of 11S abundance on functionality within an unfractionated protein matrix. The low abundance of 11S in pea protein did not seem to be the cause of inferior properties. In fact, 7S vicilin had 6-fold higher gel strength and 5-fold higher emulsification capacity, but significantly lower nutritional quality, than 11S legumin. Despite having significantly higher sulfur-containing amino acids, high protein polymerization in 11S legumin contributed to relatively low functionality. Further, fractionation induced unique changes to amino acid composition, resulting in significantly lower amino acid scores for isolated 7S vicilin and 11S legumin relative to pea protein isolate. Accordingly, 11S legumin enrichment of pea protein isolate did not improve functionality or nutritional quality. Nevertheless, this work contributed foundational knowledge that will provide direction for future studies aiming at devising strategies to improve the quality and consistency of pea protein ingredients.

Yield stress of in-situ polymerization modified cement paste

Achieving desired yield stress is crucial for various construction processes, especially in the emerging 3D concrete printing. In this paper, we present the possibility of enhancing yield stress of cement paste through in-situ polymerization and uncover the mechanisms of in-situ polymerized polymers. We investigate the effects of two types of in-situ polymerized polymer, sodium polyacrylate (PAAS) and polyacrylamide (PAM), on the yield stress, interstitial solution viscosity, and flocculated structure, as well as their adsorption behaviors on the surface of cement particles. The results show that the yield stresses of both in-situ polymerization modified cement pastes are raised considerably at high polymer concentration, which can be attributed to the dual roles of generated polymers. On the one hand, the absorbing polymers can bridge cement particles together, resulting in an augmentation in the interparticle forces. On the other hand, the non-adsorbing polymers remaining in the interstitial solution interact with each other and create a robust polymer network that can effectively withstand the external stresses. The former mechanism emerges as the dominant contributor to the enhanced yield stress of cement paste modified with in-situ polymerized PAAS, attributed to the Freundlich multilayer adsorption behavior of PAAS amplifying the bridging effect of polymers. While in-situ polymerized PAM predominantly assume the latter role, largely due to the remarkable length of their chain structure and the abundant residual polymers in the interstitial solution, which greatly intensities the interaction between polymers.

Preparation, characterization, and retarding mechanism of high temperature resistant amphoteric ion polymer oil well cement retarderPoly‐AAMDforHTHPapplication

AbstractThe amphoteric ion polymer cement retarder Poly‐AAMD was synthesized by aqueous solution polymerization, the chemical structure, molecular weight, and thermal stability was studied. As a result, theMnandMware 1.3 × 104and 4.7 × 104 g/mol, respectively, and the initial decomposition temperature is 260°C. Then, the effects of retarder Poly‐AAMD on the application performance of cement slurry, such as settlement stability, thickening time, compressive strength, and rheological properties, were investigated. Especially, the thickening time of cement slurry with 1.2 and 1.5 wt% retarder Poly‐AAMD is 312 and 316 min at 220°C, the compressive strength is larger than 14 MPa at 24 h. Compared to conventional retarders, the temperature resistance has been improved to 220°C. Simultaneously, the initial hydration process of cement slurry was studied by low field NMR based on theT2value. Moreover, the hydration products of cement slurry with retarder Poly‐AAMD were analyzed depends on the qualitative and quantitative analysis methods, the type and content of hydration products were confirmed by the methods of X‐ray diffraction analysis (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TG), and differential thermal analysis (DTG). Finally, the retarding mechanism of retarder Poly‐AAMD was further studied depends on the results of adsorption amount and Zeta potential.

A comprehensive review of viscoelastic polymer flooding in sandstone and carbonate rocks

Polymer flooding is a proven chemical Enhanced Oil Recovery (cEOR) method that boosts oil production beyond waterflooding. Thorough theoretical and practical knowledge has been obtained for this technique through numerous experimental, simulation, and field works. According to the conventional belief, this technique improves macroscopic sweep efficiency due to high polymer viscosity by producing moveable oil that remains unswept after secondary recovery. However, recent studies show that in addition to viscosity, polymer viscoelasticity can be effectively utilized to increase oil recovery by mobilizing residual oil and improving microscopic displacement efficiency in addition to macroscopic sweep efficiency. The polymer flooding is frequently implemented in sandstones with limited application in carbonates. This limitation is associated with extreme reservoir conditions, such as high concentrations of monovalent and divalent ions in the formation brine and ultimate reservoir temperatures. Other complications include the high heterogeneity of tight carbonates and their mixed-to-oil wettability. To overcome the challenges related to severe reservoir conditions, novel polymers have been introduced. These new polymers have unique monomers protecting them from chemical and thermal degradations. Monomers, such as NVP (N-vinylpyrrolidone) and ATBS (2-acrylamido-2-methylpropane sulfonic acid), enhance the chemical resistance of polymers against hydrolysis, mitigating the risk of viscosity reduction or precipitation in challenging reservoir conditions. However, the viscoelasticity of these novel polymers and their corresponding impact on microscopic displacement efficiency are not well established and require further investigation in this area. In this study, we comprehensively review recent works on viscoelastic polymer flow under various reservoir conditions, including carbonates and sandstones. In addition, the paper defines various mechanisms underlying incremental oil recovery by viscoelastic polymers and extensively describes the means of controlling and improving their viscoelasticity. Furthermore, the polymer screening studies for harsh reservoir conditions are also included. Finally, the impact of viscoelastic synthetic polymers on oil mobilization, the difficulties faced during this cEOR process, and the list of field applications in carbonates and sandstones can also be found in our work. This paper may serve as a guide for commencing or performing laboratory- and field-scale projects related to viscoelastic polymer flooding.

Preparation and construction mechanism of thermal conductive epoxy‐based composite via magnetic field induced orientation

AbstractBN was modified with Fe3O4 to confer it with paramagnetic responsivity. The scanning electron microscopy and energy dispersive spectrometer (EDS) results demonstrated that with the assistance of an external magnetic field, the paramagnetic BN particles within an epoxy matrix are effectively aligned along the direction of the magnetic field during the curing process of epoxy resin, hence forming continuous thermal conduction pathways. Therefore, the thermal conductivity of the epoxy‐based composite filled with 30 wt% of BN and externally applied with a 50 mT magnetic flux density was 0.7417 (W/m·K), an improvement of 207.89% relative to the pure epoxy resin. The establishment of continuous thermal pathways facilitates effective phonon conduction, thereby further enhancing the thermal conductivity of the material. Meanwhile, this study investigates the chain formation mechanism of Fe3O4‐modified BN under the influence of a magnetic field. When subjected to an applied magnetic field, the magnetic BN embedded in an epoxy resin matrix undergoes magnetization, rotation, and contact. Subsequently, multiple particles initially form short chains, then aggregate into longer chains aligned with the direction of the magnetic field. The findings indicate that the magnetic field induced particle alignment method holds significant potential in the fabrication of high thermal conductivity polymer composites with low filler loading.