Properties Of Polymers Research Articles

Mechanical properties of silicone polymer with magnetic filler in magnetic field

Purpose. To investigate the change in the mechanical properties of a magnetorheological silicone elastomer consisting of a polymer filled with magnetite nanoparticles under the influence of an inhomogeneous magnetic field of an electromagnet. Methods. The experiments were carried out on a magnetic response research facility developed and manufactured independently based on known methods. The value of the deflection angle of the magnetically active receiver was determined by the optical method. Two-component silicone rubbers filled with magnetite particles were studied as samples. The manufactured samples differed in geometric dimensions, magnetic phase concentrations of 1%, 5%, 10% and 20%, and polymerization mechanism. The source of the magnetic field was electromagnets of various sizes connected to power sources. The images were captured using a Micmed 5.0 digital USB microscope.Results. The analysis of the structure of the manufactured magnetorheological silicone elastomers was carried out, as well as studies of the effect of the magnetic field strength and sample parameters on the deflection angle of the magnetically active cantilever. A theoretical interpretation of the obtained results is proposed.Conclusion. The experimental dependence of the tilt angle of a magnetically active polymer cantilever on the equilibrium position relative to the magnitude of the magnetic field strength of the electromagnet is determined. The obtained research results can be used to develop actuators and magnetoactive sensors.

Chemo-Enzymatic Depolymerization of Functionalized Low-Molecular-Weight Polyethylene.

Polyethylene (PE) is the most commonly used plastic type in the world, contributing significantly to the plastic waste crisis. Microbial degradation of PE in natural environments is unlikely due to its inert saturated carbon-carbon backbones, which are difficult to break down by enzymes, challenging the development of a biocatalytic recycling method for PE waste. Here, we demonstrated the depolymerization of low-molecular-weight (LMW) PE using an enzyme cascade that included a catalase-peroxidase, an alcohol dehydrogenase, a Baeyer Villiger monooxygenase, and a lipase after the polymer was chemically pretreated with m-chloroperoxybenzoic acid (mCPBA) and ultrasonication. In a preparative experiment with gram-scale pretreated polymers, GC-MS and weight loss determinations confirmed ~27% polymer conversion including the formation of medium-size functionalized molecules such as ω-hydroxy acids and α,ω-carboxylic acids. Additional polymer property analyses using AFM showed that enzymatic depolymerization reduced the particle sizes of this mCPBA- and enzyme-treated LMWPE. This multi-enzyme catalytic concept with distinct chemical steps represents a unique starting point for future development of bio-based recycling methods for polyolefin waste.

Chemo‐Enzymatic Depolymerization of Functionalized Low‐Molecular‐Weight Polyethylene

Polyethylene (PE) is the most commonly used plastic type in the world, contributing significantly to the plastic waste crisis. Microbial degradation of PE in natural environments is unlikely due to its inert saturated carbon‐carbon backbones, which are difficult to break down by enzymes, challenging the development of a biocatalytic recycling method for PE waste. Here, we demonstrated the depolymerization of low‐molecular‐weight (LMW) PE using an enzyme cascade that included a catalase‐peroxidase, an alcohol dehydrogenase, a Baeyer Villiger monooxygenase, and a lipase after the polymer was chemically pretreated with m‐chloroperoxybenzoic acid (mCPBA) and ultrasonication. In a preparative experiment with gram‐scale pretreated polymers, GC‐MS and weight loss determinations confirmed ~27% polymer conversion including the formation of medium‐size functionalized molecules such as ω‐hydroxy acids and α,ω‐carboxylic acids. Additional polymer property analyses using AFM showed that enzymatic depolymerization reduced the particle sizes of this mCPBA‐ and enzyme‐treated LMWPE. This multi‐enzyme catalytic concept with distinct chemical steps represents a unique starting point for future development of bio‐based recycling methods for polyolefin waste.

Multi-Cover Persistence (MCP)-based machine learning for polymer property prediction.

Accurate and efficient prediction of polymers properties is crucial for polymer design. Recently, data-driven artificial intelligence (AI) models have demonstrated great promise in polymers property analysis. Even with the great progresses, a pivotal challenge in all the AI-driven models remains to be the effective representation of molecules. Here we introduce Multi-Cover Persistence (MCP)-based molecular representation and featurization for the first time. Our MCP-based polymer descriptors are combined with machine learning models, in particular, Gradient Boosting Tree (GBT) models, for polymers property prediction. Different from all previous molecular representation, polymer molecular structure and interactions are represented as MCP, which utilizes Delaunay slices at different dimensions and Rhomboid tiling to characterize the complicated geometric and topological information within the data. Statistic features from the generated persistent barcodes are used as polymer descriptors, and further combined with GBT model. Our model has been extensively validated on polymer benchmark datasets. It has been found that our models can outperform traditional fingerprint-based models and has similar accuracy with geometric deep learning models. In particular, our model tends to be more effective on large-sized monomer structures, demonstrating the great potential of MCP in characterizing more complicated polymer data. This work underscores the potential of MCP in polymer informatics, presenting a novel perspective on molecular representation and its application in polymer science.

Termination Kinetics of N‐Vinyl Formamide Radical Polymerization in Aqueous Solution

AbstractTermination kinetics of radical polymerization of N‐vinyl formamide (NVF) in aqueous solution has been measured via SP–PLP–NIR, i.e., single pulse (SP) initiation of pulsed laser polymerization (PLP) in conjunction with microsecond time‐resolved near‐infrared (NIR) detection of monomer concentration. Experiments are performed at initial NVF weight fractions from 0.20 up to bulk NVF, at monomer conversions up to 40%, and at temperatures from 40 to 70 °C as well as pressures from 500 to 2500 bar. Applying high pressure improves signal‐to‐noise quality. Data obtained upon pressure variation allow for extrapolation toward ambient pressure. The primary quantity from SP–PLP–NIR is kp/<kt>, i.e., the ratio of propagation rate coefficient, kp, to apparent chain‐length‐averaged termination rate coefficient, <kt>. With kp being available from literature, kp/<kt> yields <kt>. This quantity is relevant for modeling polymerization rate and polymer properties. Termination in the initial polymerization period turns out to be controlled by segmental diffusion and, at higher degrees of monomer conversion up to 40%, by translational diffusion.

Silane functionalization of graphene nanoplatelets

The lack of a facile route for the functionalization of highly sp2 hybridized, low oxygen content (<10 atm%, C:O > 9:1) graphene nanoplatelets (GNP) has greatly hindered full exploitation of these materials. Moreover, the highly conductive and paramagnetic properties of GNP can exclude the use of solid-state nuclear magnetic resonance spectroscopy (SS-NMR) and electron paramagnetic resonance spectroscopy (EPR), even at liquid helium temperatures, to prove binding of silane to the GNP surface is successful. Here, three model silanes, 3-Mercaptopropyltrimethoxysilane, 3-Methacryloxypropyltrimethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane were successfully bound to the surface of GNP, each following either a condensation silanization reaction or a pathway dependent on the R-group of each silane. Several techniques were employed, but critically a combination of X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis-mass spectrometry (TGA-MS) in argon and air confirmed successful binding of the silane to the GNP. The approach adopted makes available the pendant R-group on the silane for interaction or reaction with polymers and a route to significantly modifying the properties of polymers and surfaces.

Study of Graphene Oxide/Polymer Composite Membranes in Air Filtration of PM2.5

pollution, particularly the issue of fine particulate matter (PM2.5), which has emerged as a significant environmental and public health concern globally. It is particularly important to develop efficient, economical and sustainable air filtration materials to reduce the concentration of PM2.5. In this study, we investigated the potential application of some polymers such as polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN) and polyaniline (PANI) composites with graphene oxide (GO) for efficient PM2.5 filtration. These composites were found to have excellent filtration performance, thermal stability. PVDF/ GO/PI nanofiber membranes maintained stable performance under repetitive filtration cycles and high temperature conditions. PAN/GO/PI nanofiber membranes exhibited good mechanical properties and stable cycling performance.PANI/GO composites took advantage of the unique properties of the conductive polymers, and in TGA experiments, they showed minimal mass loss. Their durability and efficiency remain high even after multiple wash cycles, highlighting their potential for practical applications.

The effect of fluorinated conjugated side chains on the photovoltaic performance of polymers based on benzodithiophene (BDT) and carbazolobistriazole (CTA)

Reasonable regulation of the structure-performance relationship is extremely crucial to enhancing the device performance of organic solar cells (OSCs). As a novel fused-benzotriazole (BTA) electron-accepting (A) unit, carbazolobistriazole (CTA) has excellent luminescent properties, and the alkyl chains on the three N atoms allow flexible modulation of polymer solubility. However, higher molecular energy levels and weak crystallinity restrict the enhancement of device performance. Herein, a new donor polymer PE97 with CTA as A unit and 4,8-bis(4-(2-ethylhexyl)-3,5-difluorophenyl)benzo[1,2-b:4,5-b’]dithiophene (BDT-P2F) as electron-donating (D) unit was designed and synthesized. In comparison with the first CTA-based polymer PE93 with 4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b’]dithiophene (BDT-TF) as D unit, PE97 realizes stronger molecular stacking conducive to modulation of the active layer morphology and a deeper highest occupied molecular orbital (HOMO) level, which are favorable to increase short-circuit current density (JSC) and open-circuit voltage (VOC) of OSCs. When paired with Y-series non-fullerene acceptor eC9-2F, PE97-based OSC devices have achieved a higher power conversion efficiency (PCE) of 15.5 %, with a VOC of 0.81 V, a JSC of 25.3 mA cm−2, and a fill factor (FF) of 75.7 %, which figures significantly surpass efficiency (13.6 %) of PE93-based devices. These results indicate that the BDT-P2F unit can excellently modulate the optoelectronic properties of CTA-based polymers. This highlights the potential of the BDT-P2F as a promising D unit for polymers with weak crystallinity and limited electron-withdrawing properties.

Modulating the doping level of conductive polymers for all polymer-based triboelectric self-powered sensors

Triboelectric self-powered sensors, utilizing flexible conductive polymers in place of traditional metal electrodes, provide improved flexibility and reduced weight, making them highly promising for next-generation Internet of Things sensing applications. Here we demonstrate that ionic liquid (IL) additives notably enhance the mechanical and electrical properties of conductive polymer (PEDOT:PSS) films, optimizing their triboelectric performance. Results show that IL as molecular dopant induces structural change in PEDOT, thereby enhancing charge delocalization and doping levels. These IL-doped PEDOT:PSS films achieved high conductivity, significantly elevated surface potential, and a fourfold increase in output triboelectric voltage compared to the neat film. Additionally, flexible all-polymer tactile sensors with high sensitivity (3.6 V/kPa) were fabricated, demonstrating potential for diverse applications such as activity signal detection and human–machine interfaces.

Simulation of the effect of temperature on space charge transport in LDPE under DC electric field stress

Polymers are considered essential materials used in high-voltage direct current (HVDC) applications due to their excellent insulating properties. They are widely employed in various electrical equipment such as cables, transformers, and station insulators, providing effective protection against high currents and voltages. One of the main challenges in these applications is the effect of temperature on the performance of these insulators, as elevated temperatures can alter the electrical properties of polymers, potentially impacting the dynamics of electric charges within the material. In this work, bipolar charge transport (BCT) was used to study the effect of temperature on the dynamics of space charge in LDPE under a DC electric field. The model includes processes such as injection, migration, trapping, detrapping, and recombination. We applied a DC electric field of 50 kV/mm to low-density polyethylene (LDPE) films for 2 hours under different temperatures. The results indicate that higher temperatures significantly enhance charge mobility, leading to improved charge flux, reduced trapping, and increased detrapping of charges. This results in a more uniform distribution of the electric field within the material and a quicker transition to a steady-state condition. The increase in temperature within the applied electric field created a relative balance between trapped charge and mobile charge, indicating a positive effect of higher temperatures on the electrical insulation properties of LDPE.

Yellow-transmissive blue electrochromic polymers based on triphenylamine and ProDOT derivatives

Electrochromic polymer with yellow hue is few relative to those with other two primary colors due to its optical absorption at short wavelength of ≈ 450 nm. Triphenylamine (TPA) and its derivatives (TPAs) as chromogenic groups are frequently used to construct neutral yellow electrochromic polymers, however, those polymers based on TPAs usually exhibit low transmittance at oxidation state due to the residual absorption at short wavelength. Here, three neutral yellow electrochromic polymers (PBBE-1, PBBE-2 and PBBE-3) with different content ratios of ProDOT-10, TPA-4 and benzene were synthesized by Suzuki coupling reaction. With ProDOT-10 content in polymeric chain increasing, the oxidation potentials of polymers decrease gradually. Due to the twisted molecular structure, the absorption peaks of polymers almost remain unchanged when ProDOT-10 content in polymer reaches critical value, which provide an effective method for preparing neutral yellow electrochromic polymers. During oxidation process, PBBE-1 turns to black; PBBE-2 turns to dark blue; PBBE-3 turns to light grey, further to light blue. Through optimizing TBA-4/ProDOT-10 ratio, the electrochromic properties of polymers have been improved, such as optical contrast, response time and coloration efficiency. Especially, PBBE-3 possesses 40 % optical contrast at 435 nm, which is higher than reported TPAs based polymers at short wavelengths.

A perspective on the time‐dependent structure and properties of amorphous polymer

AbstractA molecular mechanism of viscoelastic deformation is presented. Amorphous polymers are characterized as a heterogeneous network of nanoscale cells. A “cell” is a homogeneous region within the network. Each cell phase fluctuates between the glassy and elastomer states with a period τ. The values of τ vary from cell to cell over several orders of magnitude and are strong functions of temperature. Whether a given cell responds as glassy or elastomeric depends on the ratio between its period of phase fluctuation (τj) and the period of observation (1/f), where f is the test frequency. We express this ratio, the Deborah number, as (τj × f), and present equations for modulus and energy loss as functions of (τj × f). The condition (τj × f) = 1 defines the glass transition of a cell, which arises cell‐by‐cell over a range of temperature, or over a range of time under stress. Viscoelastic deformation occurs if a cell changes phase while under stress. Energy stored during glassy state deformation is lost if the cell fluctuates to the elastomeric state. Stress is out of phase with strain, because strain rate controls the level of stress in glassy cells between phase fluctuations.Highlights A molecular mechanism of viscoelasticity is presented that does not involve viscous flow. Amorphous polymer is a heterogeneous network of nanoscale cells. Cells fluctuate in phase between glassy and elastomeric states due to their size. Time‐dependent properties are caused by time‐dependent structure. Energy is lost when glass phase cells under stress fluctuate to the elastomer phase.

Interface mechanical properties of CFRP-seawater sea sand concrete under simulated seawater immersion

In this study, the interfacial mechanical properties of carbon fiber-reinforced polymer (CFRP) sheet reinforced seawater sea sand concrete (SSSC) in simulated seawater immersion environment were studied. The results present that the interface bearing capacity of CFRP-SSSC decreases significantly after seawater immersion. The decreasing rate increases greatly with the extending of immersion periods. Seawater immersion also affects the failure mode of interface between CFRP and SSSC, which leads to the damaged surface expanding from the base layer of concrete to the junction section of resin and aggregate. The distribution of strain and stress along the bonding direction presents the load transfer from the loading end to the free end. The shear stress peak locates near the loading end and decreased about 15–20 % due to seawater immersion as a result of the deterioration of the interfacial property. The analysis on the microstructure of CFRP-SSSC interface proves that the chemical ions in seawater causes the hydrolyzation of epoxy resin adhesive layer. The CFRP-SSSC interface presents a lower interfacial bonding properties than CFRP reinforced normal concrete (NC). The improvement of strength grade of concrete from C30 to C50 increases the bonding properties of the CFRP about 9–12 % and mitigates the influence of seawater immersion. The obtained bond-slip curve indicates that the seawater immersion decreases the interface ductility. A modified Popovics model is applied to predict the bond-slip curve and presents a high fitting degree.

In Situ Microscopy of Fatigue-Loaded Embedded Transverse Layers of Cross-Ply Laminates: The Role of an Inhomogeneous Fiber Distribution

Composites with continuous fiber reinforcement offer excellent fatigue properties but are tedious to characterize due to anisotropy and the interplay of fatigue properties, processing conditions, and the constituents. The global fiber volume content can affect both monotonic and fatigue strength. This dependence can increase the necessary testing effort even when processing conditions and constituents remain identical. This work presents an in situ edge observation method, enabling light microscopy during loading. As a result, digital image correlation can be employed to study local strains at cracking sites on the scale of fiber bundles. The geometric influence on fatigue damage is examined in non-crimp fabrics of glass and carbon fibers. Two epoxy resins (one modified by irradiation) are investigated to verify the geometric influence under changed polymer properties. The microscopy-based image correlation revealed that damage forms at very low global strains of only 0.2–0.3% in glass fiber-reinforced epoxy laminates. For carbon fiber-reinforced epoxy, laminate cracking was found to emanate mainly from regions containing stitching fibers. Across both reinforcements, irradiation treatment led to delayed cracks, emanating from interfaces. This detailed analysis of the damage formation is used as a basis for proposed applications of the in situ strain information.

Non‐Ionic Perylene‐Diimide Polymer as Universal Cathode Interlayer for Conventional, Inverted, and Blade‐Coated Organic Solar Cells

AbstractAs a class of predominantly used cathode interlayers (CILs) in organic solar cells (OSCs), perylene‐diimide (PDI)‐based polymers exhibit intriguing characteristics of excellent charge transporting capacity and suitable energy levels. Despite that, PDI‐based CILs with satisfied film‐forming ability and adequate solvent resistance are rather rare, which not only limits the further advance of OSC performances but also hinders the practical use of PDI CILs. Herein, we designed and synthesized two non‐conjugated PDI polymers for achieving high power conversion efficiency (PCE) in diverse types of OSCs. The utilization of oligo (ethylene glycol) (OEG) linkage enhanced the n‐doping effect of PDI polymers, leading to an improved ability of the CIL to reduce work function and improve electron transporting capability. Moreover, the introduction of the non‐ionic OEG chain effectively improve the wetting property and solvent resistance of PDI polymers, so the PPDINN CIL can withstand diverse processing conditions in fabricating different OSCs, including conventional, inverted and blade‐coated devices. The binary OSC with conventional structure using PPDINN CIL showed a PCE of 18.6 %, along with an improved device stability. Besides, PPDINN is compatible with the large‐area blade‐coating technique, and a PCE of 16.6 % was achieved in the 1‐cm2 OSC where a blade‐coated PPDINN was used.

Non-Ionic Perylene-Diimide Polymer as Universal Cathode Interlayer for Conventional, Inverted, and Blade-Coated Organic Solar Cells.

As a class of predominantly used cathode interlayers (CILs) in organic solar cells (OSCs), perylene-diimide (PDI)-based polymers exhibit intriguing characteristics of excellent charge transporting capacity and suitable energy levels. Despite that, PDI-based CILs with satisfied film-forming ability and adequate solvent resistance are rather rare, which not only limits the further advance of OSC performances but also hinders the practical use of PDI CILs. Herein, we designed and synthesized two non-conjugated PDI polymers for achieving high power conversion efficiency (PCE) in diverse types of OSCs. The utilization of oligo (ethylene glycol) (OEG) linkage enhanced the n-doping effect of PDI polymers, leading to an improved ability of the CIL to reduce work function and improve electron transporting capability. Moreover, the introduction of the non-ionic OEG chain effectively improve the wetting property and solvent resistance of PDI polymers, so the PPDINN CIL can withstand diverse processing conditions in fabricating different OSCs, including conventional, inverted and blade-coated devices. The binary OSC with conventional structure using PPDINN CIL showed a PCE of 18.6 %, along with an improved device stability. Besides, PPDINN is compatible with the large-area blade-coating technique, and a PCE of 16.6 % was achieved in the 1-cm2 OSC where a blade-coated PPDINN was used.

Photoinduced Birefringence and Liquid Crystal Orientation on Polymers with Different Azobenzene Content in the Main Chain.

In this paper, we give an overview of novel main-chain azobenzene-based fluorinated poly(arylene ether)s with different content of azo groups, aiming at providing a better understanding of the link between a number of N═N bonds and the macroscopic response of the material. We discuss chemical synthesis and molecular structure and report on a comprehensive analysis of the polymer properties, thermal behavior, and mechanical strength. We show that a higher content of azobenzene moieties reduces the mechanical strength of the polymer materials. On the other hand, polymers with a higher content of azobenzene demonstrate higher values of induced birefringence due to a larger number of azobenzene in the trans form. The photoisomerization constants of all polymers fall within a very close range. The minor variations are attributed to the number of azobenzene groups in the polymer composition and the conformational arrangements of the polymer chain packing. The developed light-sensitive polymers were employed for dynamic control and manipulation of the liquid crystal orientation by polarization of the incident light. After the double irradiation of the substrates using appropriate photomasks, we made patterned cells that consist of domains with different high-resolution liquid crystal director orientations.

Applications of Long Short-Term Memory (LSTM) Networks in Polymeric Sciences: A Review.

This review explores the application of Long Short-Term Memory (LSTM) networks, a specialized type of recurrent neural network (RNN), in the field of polymeric sciences. LSTM networks have shown notable effectiveness in modeling sequential data and predicting time-series outcomes, which are essential for understanding complex molecular structures and dynamic processes in polymers. This review delves into the use of LSTM models for predicting polymer properties, monitoring polymerization processes, and evaluating the degradation and mechanical performance of polymers. Additionally, it addresses the challenges related to data availability and interpretability. Through various case studies and comparative analyses, the review demonstrates the effectiveness of LSTM networks in different polymer science applications. Future directions are also discussed, with an emphasis on real-time applications and the need for interdisciplinary collaboration. The goal of this review is to connect advanced machine learning (ML) techniques with polymer science, thereby promoting innovation and improving predictive capabilities in the field.

Fabrication of solar cells from polymer composite (3-Hexylthiophene-co-Thiophene) with Ag nanoparticles and study of electrical properties and efficiency

This study aims to prepare nano-polymer materials that contribute to improving the electrical properties and improving the properties and efficiency of solar cells. Also, the prepared materials are inexpensive compared to solar cells prepared from inorganic materials such as silicon and germanium. This study deals with the effect of a polymer layer containing pure polymer of 3-Hexylthiophene and Thiophenein combination with silver nanoparticles on the electrical properties relevant to solar cell applications. The polymer of 3-Hexylthiophene and Thiophene was prepared individually, then a polymer composite (3-Hexylthiophene-co-Thiophene) was made. after that then a Core-Shell of (3-hexylthiophene - CO-Thiophene) @ Ag Nanoparticles was made, after which two-layer and three-layer solar cells were made from the prepared samples. The polymers were manufactured using the additive polymerization method using chloroform (CHCl3) solvent and were subsequently characterized. The research focused on the electrical properties of the pure polymer (P3HT@Thio) doped with silver nanoparticles and its efficiency, with special attention to its application in solar cells. We found the best results in the two-layer structure. Current-voltage (I-V) measurements were conducted under illumination at room temperature with varying incident light intensities over a small area. Key parameters such as electrical conductivity, activation energy, open-circuit voltage (Voc), short-circuit current density (Jsc), maximum power point parameters (JP, VP), fill factor (FF), and power conversion efficiency (η) were calculated for all samples under standard laboratory conditions. The results demonstrate that the highest electrical conductivity (2.39x10⁻³ s.cm⁻¹) was achieved with the polymer blend of 70% P3HT-CO-30% PTH doped with 25% silver nanoparticles (Ag NPs). The activation energy, ranging from 0.1448 eV to 0.8537 eV, showed the lowest value at the same polymer blend, likely due to the proximity of the conduction and valence band levels induced by nanoparticle doping. Additionally, the efficiency of the solar cells was assessed, revealing significant improvements in device performance. The optimal efficiency, measured at 10.488%, was observed in the (PEDOT)/ (PCPM+Active Layer) structure. All relevant parameters, including Jsc, Voc, FF, and power conversion efficiency (PCE).

Prediction and investigation of water repeated absorption and release properties of superabsorbent polymers during the dry-wet cycles in different solutions

Superabsorbent polymers (SAP) with a three-dimensional cross-linked network structure are used in the concrete field due to their good water absorption and water retention properties. The changes of its repeated water absorption and release properties have an important impact on crack healing, but there is still a lack of relevant research. This study mainly uses the tea-bag method to explore the repeated water absorption and release behavior of sodium polyacrylate and polyacrylic acid-acrylamide copolymers in deionized water, cement filtrate, and saturated calcium hydroxide solution. The quantitative analysis of the change in the peak area of the water-absorbing functional group was performed by fourier transform infrared spectroscopy. The morphology and elements of SAP under different dry-wet cycles were analyzed by scanning electron microscope-energy spectrum analysis. The repeated swelling behavior of SAP was predicted using the classical models. The results showed that the repeated water absorption performance of SAP gradually decreased with the increase of the number of wet-dry cycles. The slope of the curve for the second-order equation gradually increases, and the peak area corresponding to the carboxyl functional group also gradually increases. And the rate and amount of water release gradually increase. For sodium polyacrylate, with the increase in the number of wet-dry- cycles, the increase in the content of calcium, magnesium, and aluminum elements is accompanied by a significant decrease in the content of sodium elements. In contrast, the calcium content on the surface of polyacrylic acid-acrylamide copolymer increased, but the sodium content only slightly decreased.