Polymerization Medium Research Articles

Scalable absorber with tuneable water supply fabricated via centrifugal spinning for highly efficient and stable solar-driven interfacial desalination

Although realising tuneable water supply in photothermal evaporation is an effective way to boost solar-driven interfacial evaporation for water desalination, simultaneously achieving continuous water transport and appropriate water content in evaporators remains a significant challenge. To address this challenge, centrifugal spinning technology is proposed herein to fabricate a scalable, flexible and stable photothermal evaporator from a hydrophilic (polyacrylonitrile, (PAN)) and hydrophobic polymer medium (polyurethane, (PU)). Efficient water management can be realised by tuning the parameters of polymer materials to permit vapour escape and achieve salt resistance. In addition, the arched design of the evaporator allows for omnidirectional evaporation, which enhances the photothermal conversion efficiency. The scalable centrifugal spinning nonwoven membrane-based arched evaporator prepared at the optimal hydrophilic–hydrophobic polymer ratio (21 wt% PAN and 2 wt% PU) after polypyrrole modification (PPy/21PAN/2PU CSMAE) offers a highly efficient evaporation rate of 1.82 kg m−2 h−1 with photothermal efficiency of 97.33 % under 1-sun illumination and excellent salt resistance against high-salinity brine (10 wt%). Thus, the unique properties of centrifugal spinning technology enable the large-scale preparation application of multicomponent polymeric materials for realising tuneable water supply in solar-driven interfacial evaporation and desalination.

Noncovalent functionalisation of polyaniline with the ionic liquid: An unneeded asset to prepare the emeraldine salt form of polyaniline using protic ionic liquids as polymerisation medium

Noncovalent functionalisation of polyaniline with the ionic liquid: An unneeded asset to prepare the emeraldine salt form of polyaniline using protic ionic liquids as polymerisation medium

Formation of microstructure in rail steel grinding balls depending on quenching medium parameters

Studies of the formation of microstructure of grinding balls from the rejects of rail steel were carried out during their quenching in various polymer media. At the first stage, based on studies of the cooling capacity of solutions of polymers PCM and Thermovit with varying concentrations and temperatures, the authors constructed the cooling curves of grinding balls made of K76F rail steel. It was found that at concentration of these polymers in an aqueous solution of 2 and 4 %, cooling rate of grinding balls made of K76F steel is almost identical at solution temperatures of 20 and 30 °C and significantly decreases when the temperature of the polymer solution increases to 40 °C. At the same time, the most noticeable decrease in the cooling rate is characteristic of PCM polymer with its concentration at the level of 2 %. At the second stage, the authors carried out metallographic studies of the microstructure of grinding balls made of K76F rail steel, which were quenched in laboratory conditions using polymers PCM and Thermovit with concentrations of 2 – 4 % and temperature of 20 – 40 °C. As a result, it was determined that the use of the PCM solution for quenching balls provides a significantly higher quality of microstructure and hardness of heat-treated balls compared to the use of the Thermovit polymer. At the same time, varying the concentration and temperature of the PCM polymer quenching medium allows one to obtain grinding balls with different performance characteristics that determine the potential areas of their application. Thus, quenching of balls in a solution of the specified polymer with concentration of 2 % and temperature of 20 – 30 °C ensures the production of balls with high hardness (corresponding to the IV hardness group according to the state standard GOST 7524 – 2015), and the use of a solution of the same polymer with concentration of 4 % and temperature of 20 – 30 °С for quenching creates the possibility of producing balls with lower hardness, but potentially high impact resistance.

Formation of Cluster-Structured Metallic Filaments in Organic Memristors for Wearable Neuromorphic Systems with Bio-Mimetic Synaptic Weight Distributions.

With increasing demand for wearable electronics capable of computing huge data, flexible neuromorphic systems mimicking brain functions have been receiving much attention. Despite considerable efforts in developing practical neural networks utilizing several types of flexible artificial synapses, it is still challenging to develop wearable systems for complex computations due to the difficulties in emulating continuous memory states in a synaptic component. In this study, polymer conductivity is analyzed as a crucial factor in determining the growth dynamics of metallic filaments in organic memristors. Moreover, flexible memristors with bio-mimetic synaptic functions such as linearly tunable weights are demonstrated by engineering the polymer conductivity. In the organic memristor, the cluster-structured filaments are grown within the polymer medium in response to electric stimuli, resulting in gradual resistive switching and stable synaptic plasticity. Additionally, the device exhibits the continuous and numerous non-volatile memory states due to its low leakage current. Furthermore, complex hardware neural networks including ternary logic operators and a noisy image recognitions system are successfully implemented utilizing the developed memristor arrays. This promising concept of creating flexible neural networks with bio-mimetic weight distributions will contribute to the development of a new computing architecture for energy-efficient wearable smart electronics.

Programming and Reprogramming the Viscoelasticity and Magnetic Response of Magnetoactive Thermoplastic Elastomers.

We present a novel type of magnetorheological material that allows one to restructure the magnetic particles inside the finished composite, tuning in situ the viscoelasticity and magnetic response of the material in a wide range using temperature and an applied magnetic field. The polymer medium is an A-g-B bottlebrush graft copolymer with side chains of two types: polydimethylsiloxane and polystyrene. At room temperature, the brush-like architecture provides the tissue mimetic softness and strain stiffening of the elastomeric matrix, which is formed through the aggregation of polystyrene side chains into aggregates that play the role of physical cross-links. The aggregates partially dissociate and the matrix softens at elevated temperatures, allowing for the effective rearrangement of magnetic particles by applying a magnetic field in the desired direction. Magnetoactive thermoplastic elastomers (MATEs) based on A-g-B bottlebrush graft copolymers with different amounts of aggregating side chains filled with different amounts of carbonyl iron microparticles were prepared. The in situ restructuring of magnetic particles in MATEs was shown to significantly alter their viscoelasticity and magnetic response. In particular, the induced anisotropy led to an order-of-magnitude enhancement of the magnetorheological properties of the composites.

Simple Iron Halides Enable Electrochemically Mediated ATRP in Nonpolar Media.

An electrochemically controlled atom transfer radical polymerization (eATRP) was successfully carried out with a minimal amount (ppm-level) of FeBr3 catalyst in a nonpolar solvent, specifically anisole. Traditionally, nonpolar media have been advantageous for Fe-based ATRP, but their low conductivity has hindered any electrochemical application. This study introduces the application of electrocatalytic methods in a highly nonpolar polymerization medium. Precise control over the polymerization was obtained by employing anhydrous anisole with only 400 ppm of FeBr3 and applying a negative overpotential of 0.3 V. Additionally, employing an undivided cell setup with two simple iron wire electrodes resulted in a significant 15-fold reduction in electrical resistance compared to traditional divided cell setups. This enabled the production of polymers with a dispersity of ≤1.2. Lastly, an examination of kinetic and thermodynamic aspects indicated that the ppm-level catalysis was facilitated by the high ATRP equilibrium constant of Fe catalysts in nonpolar environments.

Improvement of humic acid (HA) removal using a new inorganic-organic composite coagulant: α-costic acid as a modifier of polyaluminum chloride properties.

In this work, α-costic acid (αCA), a plant sesquiterpenoid from Dittrichia viscosa, was grafted into polyaluminum chloride (PAC), forming a new eco-sustainable composite coagulant PAC-αCA with improved functionality. The α-costic acid fraction grafted into the PAC and the distribution of aluminum forms in the composite coagulant were evaluated for their effectiveness in removing bentonite and humic acid from synthetic water. The interaction mechanism between PAC and α-CA was examined by the Al-Ferron time spectrophotometric method, density functional theory (DFT), and FTIR analysis. By monitoring the aluminum speciation in the composite coagulant PAC-αCA, it was discovered that the introduction of α-CA impacted the distribution of various aluminum forms, including mononuclear Ala, highly polymeric Alb, colloidal, and medium polymeric Alc. The theoretical analysis identified the Alb species as particularly sensitive to reacting with α-CA. Furthermore, coagulation performance tests demonstrated that increasing the percentage of α-CA and promoting the prevalence of Alb and Alc species over Ala species in PAC-αCA led to improved removal of turbidity and UV254. This study provides an attractive and practical option for water treatment plants to remove colloidal suspensions in raw water effectively.

Semiconductor quantum dots as a mechanism to enhance charge transfer processes in polymer solar cells

The light trapping capability of thin film polymer solar absorber, composed of poly (3-hexylthiophene) and [6,6]–phenyl C61- butyric acid methyl ester (P3HT:PC60BM) blend, is improved using ZnS semiconductor quantum dots (QD) as third donor-acceptor (D:A) component. The inherent characteristics of the microwave-assisted synthesized ZnS QD, such as quantum size effect, and multiple exciton generation were leveraged in harvesting high energy photons, which resulted in a better exciton generation, dissociation, and effective charge transport in the polymer medium. The synthesized QD exhibited good phase purity, effective kinetic enhancement, and control of the aggregation process. Hence, the impact of ZnS QD on the performance of thin film polymer solar cells (TFPSC) is evident by a remarkable improvement in the measured photovoltaic parameters. Nonetheless, it is observed that the device performances are generally dependent on the concentration of the QD in the absorber layer. Consequently, the power conversion efficiency has increased by 58% at 3% concentration of QDs by weight. This is an interesting development of TFPSC fabricated under an ambient environment.

Disorder‐Enhanced Charge‐Transfer‐Mediated Room‐Temperature Phosphorescence in Polymer Media

AbstractRoom‐temperature phosphorescence (RTP) polymers have important applications for biological imaging, oxygen sensing, data encryption, and photodynamic therapy. Despite the many advantages polymeric materials offer such as great control over gas permeability and processing flexibility, disorder is traditionally considered as an intrinsic negative impact on the efficiency for embedded RTP luminophores, as various allowed thermal motions could quench the emitting states. However, we propose that such disorder‐enabled freedoms of microscopic motions can be beneficial for charge‐transfer‐mediated RTP, which is facilitated by molecular conformational changes among different electronic transition states. Using the “classic” pyrene‐aniline exciplex as an example, we demonstrate the mutual enhancement of red/near‐infrared and green RTP emissions from the pyrene and aniline moieties, respectively, upon doping the aniline polymer with trace pyrene derivatives. In comparison, a pyrene‐doped crystal formed with the same aniline structure exhibits only charge‐transfer fluorescence with no red or green RTP observed, suggesting that order suppresses the RTP channels. The proposed polymerization strategy may be used as a unified method to generate multi‐emissive polymeric RTP materials from a vast pool of known and unknown exciplexes and charge‐transfer complexes.

Cohesive crack growth in polyethylene considering Schapery equation using XFEM

A nonlinear rate-dependent cohesive rule based on a novel incorporation by Schapery nonlinear coefficients is suggested to model crack growth in the case of polyethylene which is well-defined through the Schapery nonlinear constitutive equation. As the matter between the crack faces in a polymeric medium like polyethylene may tolerate large strain ranges during crazing and before complete separation, it may involve stress-dependent factors as same as bulk material. A useful damage-creeping cohesive rule is selected and its creeping part is extended in a way to incorporate the nonlinear Shapery parameters. The augmented relation is fitted to both high and low constraint results and applied to an experimented medium using Extended Finite Element Method (XFEM) to evaluate its ability to properly predict cohesive crack propagation. The results are in tight agreement with the existing experimental outputs. The suggested framework may illuminate a way of expressing the damage zone in polymers using nonlinear specifications of the bulk material.

Low-energy α-particle irradiation of polymeric-based nanofiller

In this study, the induced defects and modifications enhanced by alpha particle on CdO and ZnSe-doped polymethyl methacrylate (PMMA) were investigated. Casting method was used to prepare three sets of thin polymeric sheets doped with variable concentrations of the selected fillers. The prepared CdO and ZnSe particles were in the range 3–21 nm. The samples were irradiated with 4.5 MeV α-particle emitted from 241Am radioactive source at gradually increased fluence. The enhanced change that occurred in the physical properties for both types of samples due to α-particle irradiation was measured using Fourier transform infrared (FTIR), X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Vis), photoluminescence (PL) spectroscopy. All the pristine samples exhibited two separated direct band gaps around 4.0 eV and 4.6 eV, while the irradiated samples showed decreasing for the first band gap up to 3.71 and the second gap remained almost unchanged. The three investigated sets displayed PL emission peaks within the range 270–700 nm. The intensity of the PL peaks was increased by increasing the filler concentration. The net PL was quantified using the area under the emission peaks which showed that α-particle causes interchangeable defects and cross-linking processes. The formation of C–H and O–H function groups due to α-particle interactions was confirmed by FTIR analysis. The results revealed that the filler–polymer interface has a great impact on the formed defects which control the observed characteristics in the polymeric composite medium. The presented data are very helpful for α-particle dosimetric applications using these types of polymeric composites.

Preparation and Characterizations of PVA/Vanadium Nanocomposites for Gamma Ray Shielding and Antibacterial Activity Applications

The biological use of nanocomposites (NCs) is highly intriguing and is more acknowledged for its value, particularly in nanomedicine. The key goal of this study is to investigate the influence of vanadium nanoparticles (VNPs) addition on PVA’s morphological, optical, and electrical properties. In this work, the PVA/V nanocomposites (NCs) were fabricated with different VNP contents of (0.02, 0.04, and 0.06) wt.% by the casting solution technique. The optical microscopy (OM) and scanning electron microscope (SEM) have been used to examine the surface morphological features of produced films, which showed that the VNP clusters were well dispersed in the polymer medium. The intermolecular interaction of the PVA/V nanocomposite was studied by FTIR examination. The interaction between PVA and V was confirmed by observing the change in IR absorption intensity. The UV–Vis approach was used to explore the optical characteristics of the UV–Vis region. The experimental data demonstrate that variations in the concentration of VNPs significantly impact the absorption. For the doped samples, the absorbance against wavelength is exponential. There is evidence of interface between polymer and nanoparticles because the optical band gap has shrunk from 4.50 eV to 3.30 eV, with a corresponding narrowing of the gap between the valence and conduction bands. The electrical characteristics of alternating current were investigated in the frequency range of 100–5 MHz. The dielectric constant and loss of NC films reduced as the concentration of VNPs rose, whereas electrical conductivity increased. With rising VNPs, the attenuation coefficient values rose. The inhibition zone diameters of Staphylococcus aureus bacteria increased with the increase of VNP contents. We showed that adding polyvinyl alcohol (PVA) to V composites increases their antimicrobial (ANB) activities. Based on these findings, NC films can be used for gamma-ray protection and antimicrobial (ANB) purposes.

Oxygen Tolerance during Surface-Initiated Photo-ATRP: Tips and Tricks for Making Brushes under Environmental Conditions.

Achieving tolerance toward oxygen during surface-initiated reversible deactivation radical polymerization (SI-RDRP) holds the potential to translate the fabrication of polymer brush-coatings into upscalable and technologically relevant processes for functionalizing materials. While focusing on surface-initiated photoinduced atom transfer radical polymerization (SI-photoATRP), we demonstrate that a judicious tuning of the composition of reaction mixtures and the adjustment of the polymerization setup enable to maximize the compatibility of this grafting technique toward environmental conditions. Typically, the presence of O2 in the polymerization medium limits the attainable thickness of polymer brushes and causes the occurrence of "edge effects", i.e., areas at the substrates' edges where continuous oxygen diffusion from the surrounding environment inhibits brush growth. However, the concentrations of the Cu-based catalyst and "free" alkyl halide initiator in solution emerge as key parameters to achieve a more efficient consumption of oxygen and yield uniform and thick brushes, even for polymerization mixtures that are more exposed to air. Precise variation of reaction conditions thus allows us to identify those variables that become determinants for making the synthesis of brushes more tolerant toward oxygen, and consequently more practical and upscalable.

Computational investigation of the effect ZnS buffer layer on the hole transport of polymer solar cell

Semiconductor organic solar absorber exhibits poor charge transport process because of exciton short diffusion length, short life time, and poor carrier mobilities in the medium. Such transport properties have negatively impacted the performance of organic solar cells (OSC). This article is designed to investigate the effect of solar absorber thickness and metal plasmonic nanoparticles using the most popular polymer blend (P3HT:PCBM) via SCAPS device simulation program. Bulk hetero-junction (BHJ) design of OSC has partially addressed the challenges by increasing inter-facial area of the acceptor/donor (A/D) molecules, which boosts the generation of free charges. However, the collection of these charges hindered due to low carrier mobilities in polymer medium. Significant influence of the Zinc Sulfide (ZnS) metal nanoparticles (NPs) have been observed on the performance of OSC at various concentrations. Thus, we are reporting here the effect of absorber layer thickness and ZnS NPs on the charge transport process in OSC.

Suppressing charge recombination in disordered polymers blend medium

Charge recombination is one of the critical factors that influences the performance of thin film polymer solar cells (TFPSCs). In this investigation, metal, plasmonic nano-particles are employed to suppress charge recombination and energy loss in TFPSC. Trimetallic nano-composite (NC) was successfully synthesized and composed of copper, nickel, and silver (Cu/Ni/Ag) using wet chemistry. The NC was incorporated into polymer-based solar absorber layers at different concentrations. The absorber layer is a fullerene-based bulk-heterojunction design using poly-3-hexylthiophene (P3HT) donor polymer. The results show that the power conversion efficiency of the device doped with NC has improved by 85% compared to the undoped one. The incorporation of tri-metallic NC into the polymer blend solar absorber resulted in enhanced optical absorption and improved collection of photo-current as reflected by the recorded high short circuit current density (J ) and fill factor. The enhancement of the performance is due to the occurrence of local surface plasmon resonances in the polymer medium. The experiment indicated that there is some increment in an open circuit voltage, which is attributed to the low energy losses as a result of improved exciton dissociation, charge carrier transport, and collection.

Biodegradable waterborne polyurethane‐urea dispersion adhesives with high biocontent

AbstractNon‐biodegradable petroleum‐based plastic wastes have become a leading environmental concern, and new efforts are underway to prepare biobased and biodegradable replacements. We have explored the preparation of adhesives suitable for use in consumer products, and here we report the development of waterborne, biodegradable adhesives from biobased monomers resulting in adhesives exceeding 70% biocontent. Using water as the polymer medium, viscosity challenges and the use of volatile organic solvents are avoided. Material properties of the polyurethane dispersions, resulting films, and laminates produced showed Mw ranging between 56,000 and 124,000. Lastly, the biodegradability of films and laminates was evaluated. The resulting metrics indicate that the adhesives produced meet the desired mechanical and biodegradability targets, indicating that high renewability content solvent‐free polyurethane dispersions are a viable solution for lamination adhesives.

Influence of polymer solution concentration and media permeability on the residual resistance factor

Purpose. Determination of the required concentration of polymer solution, providing the maximum well insulation effect, depending on the filtration characteristics of the medium. Methodology. The research was conducted by experimental method using the methodology of planning the experiment. The theory of rational planning was used by varying two variables on five levels. Media permeability and polymer solution concentration were used as variables. Methods of mathematical statistics were used in processing the results. Findings. Experimental studies made it possible to build a model expressing the dependence of the residual resistance factor on the permeability of the medium and the concentration of the polymer solution. By further statistical processing the connection between permeability and necessary concentration of polymer solution was obtained. Originality. The experimental studies have substantiated the possibility of evaluating the influence of medium permeability and concentration of polymer solution on the residual resistance factor and determined its dependence on the concentration of polymer solution and medium permeability. The main point of polymer solutions application is justification and choice of the reagent concentration. The concentration should be selected in such a way that it provides the maximum value of the residual resistance factor and the viscosity of the solution necessary to level out permeability heterogeneity of the environment to some extent. To achieve this, a relationship has been obtained that allows determining the concentration of the polymer solution at a given permeability of the environment that provides the maximum residual resistance factor. Practical value. The conducted experimental studies allow developing the ideas about the regularities of water manifestations. The results of the research allow selecting purposefully both the formulations of composite systems and the technology of their application to improve the efficiency of oil production and to limit water inflows in specific geological and physical conditions.

Novel lead-free 2–1–2 composite: predicted high piezoelectric sensitivity and significant hydrostatic response

A parallel-connected composite with 2–1–2 connectivity and two lead-free single-crystal (SC) components is proposed. Its high piezoelectric sensitivity is highlighted and its large hydrostatic parameters are described. The first type of composite layer represents a ferroelectric domain-engineered [001]-poled [Li, (K, Na)](Nb, Ta)O3 SC. In the second type of composite layer, piezoelectric Li2B4O7 SC rods in the form of an elliptic cylinder are regularly aligned in a large polymer matrix. The effective electromechanical properties of the composite were found in three stages, using the effective field and matrix methods that are applicable to piezoelectric media. A new orientation effect was studied, linked with rotations of SC rod bases in the polymer medium that forms the second type of layer. Since these rotations are in a Li2B4O7 SC with a unique elastic and piezoelectric anisotropy, the second type of layer exhibits a noticeable influence on the piezoelectric performance and hydrostatic response of the composite. A variation of the aspect ratio of the Li2B4O7 rod base becomes another important factor that can improve the hydrostatic parameters of the composite. Some effective parameters of related 2–1–2 composites were compared for different polymer components. Three diagrams were first constructed for the high-performance 2–1–2 [Li, (K, Na)](Nb, Ta)O3/Li2B4O7/polyethylene composite to show the ranges of rotation angles and volume fractions that correspond to the longitudinal piezoelectric voltage coefficient > 500 mV m N−1, hydrostatic piezoelectric coefficient > 200 mVm N−1 and hydrostatic figure of merit >10−11 Pa−1. These effective parameters are important in piezoelectric sensors and hydroacoustic and other applications of novel lead-free composites.

Modeling the CO2 separation capability of poly(4-methyl-1-pentane) membrane modified with different nanoparticles by artificial neural networks

Membranes are a potential technology to reduce energy consumption as well as environmental challenges considering the separation processes. A new class of this technology, namely mixed matrix membrane (MMM) can be fabricated by dispersing solid substances in a polymeric medium. In this way, the poly(4-methyl-1-pentene)-based MMMs have attracted great attention to capturing carbon dioxide (CO2), which is an environmental pollutant with a greenhouse effect. The CO2 permeability in different MMMs constituted of poly(4-methyl-1-pentene) (PMP) and nanoparticles was comprehensively analyzed from the experimental point of view. In addition, a straightforward mathematical model is necessary to compute the CO2 permeability before constructing the related PMP-based separation process. Hence, the current study employs multilayer perceptron artificial neural networks (MLP-ANN) to relate the CO2 permeability in PMP/nanoparticle MMMs to the membrane composition (additive type and dose) and pressure. Accordingly, the effect of these independent variables on CO2 permeability in PMP-based membranes is explored using multiple linear regression analysis. It was figured out that the CO2 permeability has a direct relationship with all independent variables, while the nanoparticle dose is the strongest one. The MLP-ANN structural features have efficiently demonstrated an appealing potential to achieve the highest accurate prediction for CO2 permeability. A two-layer MLP-ANN with the 3-8-1 topology trained by the Bayesian regulation algorithm is identified as the best model for the considered problem. This model simulates 112 experimentally measured CO2 permeability in PMP/ZnO, PMP/Al2O3, PMP/TiO2, and PMP/TiO2-NT with an excellent absolute average relative deviation (AARD) of lower than 5.5%, mean absolute error (MAE) of 6.87 and correlation coefficient (R) of higher than 0.99470. It was found that the mixed matrix membrane constituted of PMP and TiO2-NT (functionalized nanotube with titanium dioxide) is the best medium for CO2 separation.

Spectral and photophysical characteristics of asymmetric polymethine dyes in polyurethane matrices

Effects of the polymer matrix polarity on the spectral and photophysical properties of asymmetric polymethine dyes were investigated. Asymmetrical cyanines of the LDS (laser dye styryl) series were used, which were introduced into elastic polyurethane matrices by an auxiliary solvent. Polymer media were synthesized by: a polyaddition reaction based on macrodiisocyanate from oligoethylene glycol adipinate, hexamethylene diisocyanate, trimethylolpropane, and a photopolymerization reaction of oligourethane acrylate with benzoin isobutyl ether. Polyurethane polarity influence on the absorption and luminescence band maxima, and the Stokes shift of the dye spectra was studied, and the obtained spectral parameters of dyes in the polymer matrices were compared with the corresponding characteristics of their ethanol solutions. The observed spectral peak positions of the absorption and luminescence bands, changes in the Stokes shift value for the LDS dyes in different environments indicated the presence of positive solvatochromism. The presented results demonstrated the possibility of the significant increase in photostability of asymmetric polymethine dyes in the polymer polyurethane matrix of high polarity, obtained by means of the polyaddition reaction.