Search Results (268)

Conductive core–shell superabsorbent polymers (SAPs) are emerging as multifunctional additives for cementitious materials, combining moisture management with electrical functionality. In cement-based systems, a swellable polymeric core enables internal curing and crack-sealing through controlled water uptake and release, while a conductive shell introduces ionic and/or electronic charge transport, addressing key limitations of conventional non-conductive SAPs. This dual functionality provides a pathway toward smart cementitious composites with enhanced durability, self-sensing capability, and moisture-responsive behavior. This review focuses on the physical chemistry mechanisms governing conductive core–shell SAPs in cementitious environments, with emphasis on swelling thermodynamics, water transport kinetics, interfacial phenomena, and charge transport mechanisms. The roles of osmotic pressure, elastic network constraints, ionic effects, and pore solution chemistry are critically discussed, together with their impact on conductivity, hydration processes, microstructure development, and long-term performance. The relative contributions of ionic and electronic conduction are examined in relation to hydration state, shell morphology, and percolation of conductive networks. In addition, the relevance of core–shell SAP architectures to sustainable packaging is briefly discussed as a secondary application, illustrating how similar physicochemical principles—such as moisture buffering and functional coatings—apply beyond construction materials. Finally, key knowledge gaps are identified, including long-term stability in highly alkaline environments, trade-offs between swelling capacity and conductivity, environmental impacts of conductive phases, and the need for integrated experimental and modeling approaches. Addressing these challenges is essential for the rational design and practical implementation of conductive core–shell SAPs in next-generation cementitious materials. Full article

Conventional admixture-based self-healing technologies are often limited by inadequate internal water supply and a scarcity of unhydrated gel particles. Therefore, this study proposes a new self-healing method that leverages the synergistic interplay between the chemical repair of sodium silicate and the physical clogging of superabsorbent polymers (SAPs) to overcome the aforementioned limitations. The healing efficiency of cement mortar was assessed through compressive strength recovery, capillary water absorption, and ultrasonic pulse velocity (UPV). Microstructural evolution and healing mechanisms were elucidated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results indicate that at an optimal dosage (0.5 wt.% for both admixtures), the healing performance is significantly enhanced: the compressive strength recovery rate reaches 103.1%, the capillary water absorption coefficient decreases by 16.57 × 10⁻³, and the UPV recovery achieves 95.4%. Microstructural analysis reveals that sodium silicate facilitates the reaction between ${\mathrm{Ca}}^{2+}$ and ${\mathrm{S}\mathrm{i}\mathrm{O}}_3^{2-}$ ions, leading to the in situ precipitation of dense C-S-H gel at the crack interface, thereby enabling chemical repair. In contrast, SAP contributes to physical sealing via a swelling and release mechanism. Full article

Hydrogels have emerged as promising functional materials for improving water management and nutrient delivery in agriculture, particularly under conditions of increasing water scarcity and declining soil fertility. However, most commercially available superabsorbent hydrogels are based on petroleum-derived polymers, raising concerns regarding their persistence in soils, potential microplastic formation and long-term environmental impact. In response, significant research efforts are being directed toward the development of biodegradable hydrogels derived from renewable biopolymers. This review provides a critical overview of recent advances in hydrogel systems designed for agricultural applications, with a particular focus on biopolymer-based materials. First, the current landscape of hydrogel technologies used as soil conditioners and controlled-release systems for agrochemicals is contextualized, highlighting the limitations of conventional synthetic hydrogels. Subsequently, the main classes of natural polymers explored for hydrogel fabrication, including polysaccharides (e.g., chitosan, alginate, cellulose and starch) and proteins (e.g., gelatin, keratin and soy protein), are analyzed in terms of raw material sources, gelation mechanisms and structure–property relationships. Their performance in key agricultural functions, such as water retention, controlled nutrient release, soil conditioning and enhancement of plant growth, is also discussed. Finally, the review identifies major challenges that currently hinder large-scale implementation, including mechanical stability, degradation behavior in complex soil environments, nutrient release control and economic scalability. By integrating recent progress and outlining emerging research directions, this work aims to support the rational design of next-generation biodegradable hydrogels capable of contributing to sustainable agriculture and circular bioeconomy strategies. Full article

Composite superabsorbents (C-SAPs) that combine synthetic and polysaccharide components hold great promise for sustainable agriculture. They improve water management and enable the controlled release of agrochemicals. However, increasing the polysaccharide content to enhance biodegradability often reduces water absorption capacity. In this study, we explore plasticization with succinic acid esters as a strategy to overcome this limitation. Our goal is to establish structure–property relationships between plasticizer architecture and C-SAP performance. A series of carboxymethyl cellulose-based superabsorbents was synthesized via radical copolymerization. They were then plasticized with 5 wt.% of dibutyl succinate, di-sec-butyl succinate, or di-iso-butyl succinate. The resulting materials were characterized using FTIR spectroscopy, differential scanning calorimetry, rheological tests, swelling kinetics, and phytotoxicity assays against oilseed radish and common oat. Increased plasticizer branching and molecular volume enhanced polymer network elasticity, lowered the glass transition temperature (by up to 6 °C), and increased the equilibrium swelling ratio by up to 64% compared to the unplasticized C-SAP (661 ± 17 vs. 402 ± 10 g/g). All plasticized C-SAPs retained more than 80% of their initial swelling capacity over five swelling–deswelling cycles across pH 3.0–9.2. They also showed no phytotoxicity at agriculturally relevant concentrations. These findings demonstrate that molecular engineering of plasticizer architecture enables simultaneous optimization of water absorption and environmental safety in C-SAPs for agricultural use. Full article

Water scarcity is increasingly challenging greenhouse tomato production, particularly in Mediterranean and semi-arid regions where irrigation water availability is becoming progressively limited. This study evaluated whether a superabsorbent polymer (SAP) can support water-saving irrigation in tomato grown in coconut fibre. Plants were cultivated in pots under four irrigation amounts (100, 75, 50, and 25% of crop water requirement—WC) combined with two SAP levels (0 and 2 g L⁻¹). Irrigation was managed by a lysimetric control system. Reducing irrigation decreased total fruit yield (averaged across SAP treatments) from 100% WC (1212 g plant⁻¹) to 50–25% WC (914 and 624 g plant⁻¹, respectively), while non-marketable fruit number was unchanged (15.4 fruit plant⁻¹, on average). SAP increased total yield, averaged across irrigation treatments (from 925 to 1022 g plant⁻¹), and marketable fruit number (from 26.3 to 32.3 fruit plant⁻¹), without affecting unitary fruit weight (20.4 g fruit⁻¹, on average). SAP also increased net photosynthesis (from 16.0 to 17.4 µmol CO₂ m⁻² s⁻¹), while stomatal conductance (0.14–0.15 mol H₂O m⁻² s⁻¹) and WUE (4.0 µmol CO₂ mmol⁻¹ H₂O) were not affected by SAP. Total soluble solids increased under severe deficit (7.8 °Brix at 25% WC) and were enhanced by SAP (from 6.9 to 7.6 °Brix), while colour parameters were mainly driven by irrigation. Overall, the irrigation amount was the primary driver of performance. Moderate deficit irrigation (75% WC) maintained a marketable fruit number and total fruit weight comparable to full irrigation (100% WC). SAP amendment acted as a complementary tool to improve marketable production and net photosynthesis across irrigation levels, providing an additive benefit to crop productivity. Full article

In agriculture, soil amendments like compost, manure, superabsorbent polymers (SAP) and biochar (BC) are already in use to mitigate the effects of water shortage and to obtain a higher yield and survivability. The present study focuses on the impact of BC and SAP under moderate and reduced soil water content (SWC) on the physiological and biochemical response of Chenopodium quinoa Willd. (cv. UDEC-5), a naturally drought-resistant and strategic crop in arid regions, with the aim of further improving its resilience and biomass production. Plants were grown in the presence or absence (control) of SAP (1% or 0.1% g/100 g SAP) or BC (3% g/100 g BC) by taking into account the smallest possible amount of irrigation necessary for optimal growth of the control. Sixty-five days after sowing, the reduced watering approaches started. The irrigation amount was reduced slowly until plants without any amendment showed a significant reduction in CO₂/H₂O gas exchange and further significant changes in 23 morphological, physiological and biochemical symptoms of water shortage. Each amendment already caused individual plant response in wet conditions: The soil amendments of SAP (1% and 0.1%) and BC had no significant effect on biomass production but caused changes in PS I (portion of oxidized and open centers in PS I), the C/N ratio and N content. The addition of SAP (0.1% and 1%) led to a decrease in gH⁺, ECStmAu ^× gH⁺, R_D, R_L, the C_i/C_atm ratio and ETR/A_gross ratio and to an increase in water use efficiency (WUE), especially in the 0.1% SAP treatment. In moderate conditions, 0.1% SAP and 3% BC caused a significant increase in both the LOP and C/N ratio. In the moderate treatments, the application of 0.1% SAP promoted an increased A_net, while 3% BC promoted a significant reduction in malondialdehyde (MDA). The results of the present quinoa experiment indicate the drought avoidance mechanism of the control under low SWC. The reduced transpiration led to increased WUE due to the efficient use of the substomatal CO₂ reservoir under low C_s and low E. It could also be confirmed that quinoa plants balanced low soil water potential by the accumulation of compatible solutes to lower the LWP and LOP. Drought led, especially in leaves in the 1% SAP treatment, to significant reductions in CO₂/H₂O gas exchange (A_net, R_D), decreases in Y (II) and ETR in PS II, and an increase in the ETR/A ratio and over-reduced centers in PS I, pointing to an increased appearance of reactive oxygen species (ROS) in the chloroplasts. The latter change was indicated by higher levels of lipid peroxidation (MDA). It could be shown that the response of the test species Chenopodium quinoa to the addition of BC and SAP proved to be highly adaptable. The plant reacted in a very coordinated and specific way to both the danger of oversupply of SAP soil amendments under water shortage conditions and an effective adaptation to a limited water supply with 3% BC and 0.1% SAP by increasing WUE and proline content. However, BC also had a mitigating effect on the level of reactive oxygen species (ROS). It can be assumed that this effect is based on a more plant-compatible, less one-sided ion composition of BC. The results presented indicate that SAP and BC can have an impact on the water and nutrient accessibility for plants. Therefore, optimal biomass production and plant response can only be reached if plant soil interactions and competition between SAP, BC and the plant roots are taken into account when planning for climate-resilient, water-saving agriculture. Full article

In drip-irrigated maize of arid Xinjiang, seedling hardening (withholding irrigation) is used to induce deep rooting, but the conventional practice of banding phosphorus (P) fertilizer without basal application creates a spatial mismatch—roots are forced downward while P remains trapped in drying topsoil. We hypothesized that co-applying superabsorbent polymer (SAP) with banded P fertilizer can form a localized, persistently hydrated P-enriched patch that synchronizes root–resource distribution. A two-year field experiment (2024–2025) was conducted with three treatments: no P (P0), banded monoammonium phosphate (B-MAP, 120 kg P₂O₅ ha⁻¹), and B-MAP + SAP (15 kg ha⁻¹). Soil properties, root growth, canopy physiology, dry matter accumulation, nutrient uptake, and grain yield were measured. Results: At the V4 stage, B-MAP + SAP increased available P and soil water content in the 0–10 cm layer by 9.4% and 16.1%, respectively, relative to B-MAP. This patch triggered vigorous root proliferation: topsoil root length at V4 rose by 23.9%, and root length density in the 30–40 cm subsoil at V9 and R1 increased by 59.0% and 36.5%. Consequently, B-MAP + SAP sustained the highest leaf area index, net photosynthetic rate, and biomass accumulation. Two-year average grain yield reached 18.2 t ha⁻¹, 9.7% and 20.7% higher than B-MAP and P0. Crucially, P use efficiency (PUE) and water productivity (WP) under B-MAP + SAP improved by 76.2% and 9.8% over B-MAP. Co-applying SAP with banded P fertilizer resolves the spatial mismatch in hardening systems, optimizes root architecture, and synergistically boosts yield, PUE, and WP. This one-time amendment offers a simple, scalable strategy for efficient P management in arid drip-irrigated maize. Full article

Menstruation, a biological phenomenon experienced by more than half of the global population, remains stigmatized and poorly addressed in the context of research and public discourse. One overlooked issue is that of “period pollution,” the waste generated by millions of feminine hygiene pads (menstrual pads) that end up in landfills or the environment. Simultaneously, Japanese knotweed (Reynoutria japonica), a non-native invasive plant which disrupts native species, leads to the disruption of ecological systems. This experimental study assesses the Japanese knotweed plant for its potential to serve as the absorbent core in a sustainable menstrual pad, helping to address both environmental challenges in tandem. As control groups, commercial pads (Natracare and Saathi) were tested for their performance as absorbent materials, as defined by the absorbency ratio (AR) test. All preliminary studies were done using normal saline solutions dyed with red food coloring. Saathi pads demonstrated significantly higher levels of AR compared to Natracare and knotweed pads due to the presence of superabsorbent polymers, making it an unreliable benchmark. Because Japanese knotweed is composed of cellulosic fibers that absorb water through hydrogen bonding to hydroxyl groups and capillary imbibition within porous fiber networks, lignin removal via alkaline processing was employed to enhance absorbency prior to experimental testing. The inner lumen of the knotweed was selected and delignified using a sodium hydroxide bath, later being shaped into an absorbent core akin to the measurements of the commercial pads and inserted into Natracare shells for proof-of-concept testing. Although knotweed-based pads exhibited lower AR values than Natracare, the testing places the knotweed prototype at approximately 40% of the fluid capacity, indicating a strong starting point for a natural fiber. To further evaluate the processing feasibility of Japanese knotweed beyond laboratory-scale pad prototyping, Japanese knotweed biomass was subjected to conventional Kraft pulping, which helps to remove lignin and increase absorbency. The Kraft pulping produced a moderately delignified brown pulp with a Kappa number of 20. Due to limiting factors, the absorbency of the pulp was not tested. However, the pulp’s fiber dimensions were comparable to hardwood pulps that are commonly used in absorbent applications, suggesting feasibility for future development into bleached fluff pulp and sustainable menstrual hygiene products. Full article

This study investigated the effects of varying water–binder (w/b) ratios and internal curing materials—superabsorbent polymer (SAP) and ceramsite—on the shrinkage behavior and crack resistance of ultra-high-performance concrete (UHPC). Although internal curing has been extensively studied, the comparative effectiveness of different internal curing materials on early-age shrinkage and restrained cracking behavior of UHPC under consistent mixture proportions remains unclear. To address this gap, a systematic experimental comparison of SAP and ceramsite was conducted. The influences of w/b ratio and different amounts and addition methods (dry and pre-absorbed addition) of SAP and ceramsite on the flowability, mechanical properties, early autogenous shrinkage, drying shrinkage, and early crack resistance of UHPC were discussed. Findings indicate that increasing the w/b ratio reduces autogenous shrinkage but compromises mechanical properties, altering the cracking mode from primary microcracks to a few wider cracks. Pre-saturated ceramsite (less than 10% volume) and SAP effectively mitigate autogenous and drying shrinkage, enhancing crack resistance without significantly reducing mechanical properties. However, exceeding a ceramsite volume dosage of 10% or using the dry addition method increased the flowability of UHPC, while decreasing crack resistance. Microstructural analysis reveals that internal curing materials facilitate hydration and enhance structural density through the formation of ettringite and calcium silicate hydrate. To optimize shrinkage reduction while maintaining mechanical properties, SAP should be incorporated in a dry state, with a dosage limited to 0.4% of the mass of the cementitious material; ceramsite needs to be pre-saturated and limited to 5% of the total volume. Full article

Plastic shrinkage and self-desiccation, along with the associated early-age cracking, are still among the most important factors that influence long-term performance of concrete structures, including durability. Superabsorbent polymers (SAPs) have been widely researched for application in concrete to mitigate shrinkage through facilitating effective internal curing by releasing water into the mixture to promote continuous hydration of cement. The acoustic emission (AE) monitoring technique, due to its high sensitivity, has proven very effective in tracking the process of water release by SAPs in concrete during early-stage curing. Typically, AE parameters such as cumulative activity, amplitude and energy are utilized to characterize the kinetics of curing processes. While these parameters indicate well the internal activity of SAPs in time, they do not offer information on the precise location of the active sources within the material’s volume, leaving a crucial gap in the understanding of the ongoing microstructural changes caused by internal water distribution and cement hydration. In this sense, AE event source localization can offer information about the active zones of water hydration activity in the material 3D domain, allowing detection of their evolution during concrete curing. Meanwhile, Acoustic Emission Tomography (AET) computes ultrasonic velocity distributions in different periods of monitoring, which are governed by acoustic characteristics of the concrete mixtures, to visualize material stiffness development spatially and temporally. This level of insight is particularly important for SAP concrete, where uniformity of internal water curing is essential for ensuring long-term durability and material soundness. By visualizing how the hydration sources evolve in real time, these methods offer an effective, non-destructive, and cost-effective solution for early-age concrete quality control, which would be challenging to achieve through other techniques. Full article

To address the limitations of conventional superabsorbent polymers in complex aqueous environments, a novel ternary composite gel (BT-SAP) based on xanthan gum, poly(acrylic acid-co-acrylamide), and bentonite was synthesized via a facile one-pot polymerization. Characterization confirmed the formation of a stable organic–inorganic hybrid three-dimensional network. The gel demonstrated outstanding comprehensive performance: a maximum water absorption capacity of 378.6 g/g; good adaptability to various pH levels, salt ions, and real water bodies; and rapid absorption kinetics and reusable potential over multiple cycles. Simultaneously, it exhibited a high adsorption capacity of 181.3 mg/g for methylene blue. The adsorption isotherm followed the Freundlich model, indicating adsorption on a heterogeneous surface. Kinetic studies revealed that the process was best described by the pseudo-second-order model, suggesting chemisorption as the rate-controlling step. XPS analysis further elucidated that the adsorption primarily occurred through the synergistic effect of electrostatic attraction from carboxyl groups and hydrogen bonding from amide/hydroxyl groups within the gel. This work provides a new strategy for developing smart materials integrating efficient water absorption and dye removal functionalities. Full article

The aim of the study was to assess the effect of superabsorbents on the condition of selected legume species grown with different watering frequencies. Three two-factor pot experiments were conducted in MICRO-CLIMA phytotrons. The objects of the study were three legume species: faba bean, pea and soybean. The first factor was the superabsorbent (SAP) rate (0, 2, 4, and 6 g·kg⁻¹ of substrate), while the second factor was the watering frequency (the subjects were watered every 1, 3, 6, and 9 days). The study showed that faba bean and pea plants were significantly taller after superabsorbent application (by 17 and 11%, respectively) and developed greater root mass. The application of SAPs at a rate of 6 g·kg⁻¹ increased the dry weight of the underground parts of faba beans and peas (by 56.8% and 85.9%, respectively) compared to the control. The highest SAP dose reduced the Fv/Fm index in soybean and the PI index in faba bean and soybean (by 5 and 29%, respectively). The lowest SPAD index in peas was recorded in the control treatment (without SAPs) and in soybeans at the highest dose of SAPs (6 g·kg⁻¹). In all species, the best results for growth and biomass of the aboveground parts were obtained with daily watering, which increased plant height by an average of 26.5–60.9% and the dry mass of the aboveground parts by 42.6–60.6% compared to less frequent watering. Higher values of the Fv/Fm index were observed in soybean, and higher values of the PI index were observed in faba bean, pea, and soybean in the least frequently watered treatments. In all species studied, the SPAD index was higher under conditions of the greatest water deficit (watering every 9 days) compared to plants watered every 1, 3, and 6 days. Full article

Superabsorbent polymers (SAPs) are materials that can absorb and retain water solutions with a mass of several hundred times greater than their own. This work aimed to synthesise and evaluate the effects of highly absorbent starch phosphate-g-poly(acrylic acid) copolymers on the microbiological activity of soils previously used for agriculture. The biopolymers studied were obtained by thermal and chemical oxidation of starch phosphates and copolymerized with potassium salts of acrylic acid. Basic physicochemical parameters were determined in the applied soil. Following SAP application, the basal respiration rate was measured at 22 °C with a constant soil moisture content of 60% WHC. The incubation time in constant temperature and moisture conditions was 78 days. After this period, their microbiological activity (microbial and organic phosphorus fractions) was assessed, thereby enabling the determination of the direction of change in the soil environment. The addition of SAP increases the soil’s water-holding capacity and respiration. The SP-g-PAA polymers serve as slow-release sources of potassium and phosphorus ions. These elements were bound to the polymer network by ionic and covalent bonds. Analysis of the results shows that within two weeks, 47–80% of the starch hydrogel undergoes microbial degradation. No differences were found in the content of labile forms of phosphorus in soils with SAP additions compared to soils without polymer additions. The use of modified starch reduces the consumption of vinyl monomers, while the resulting product is characterised by high absorbency and low water content, which reduces the amount of energy needed to obtain the finished product, thus contributing to sustainable development. Full article

Soil moisture regulation is critical for vegetation restoration in arid ecosystems. Polymeric hydrogels, notably polyacrylic acid (PAA) and polyacrylamide (PAM), are widely employed as water-retaining agents to enhance soil water availability. However, the coupling between their distinct chemical structures and key performance metrics, particularly cycling stability and water retention kinetics in desert substrates, remains unclear. In this work, we present an integrated experimental–computational study to establish a “molecular structure–interfacial behavior–macroscopic property” framework for PAA and PAM. The results show that PAA exhibits a higher equilibrium water absorption (WAC ~242 g/g) and more stable water uptake capacity under cycling, whereas PAM displays much higher zero-shear viscosity and pronounced shear thinning with a yield plateau (~30 Pa). DFT and MD simulations trace these macroscopic disparities to their distinct electronic structures and hydration dynamics. Specifically, PAA’s strong electrostatic interactions and extended chain conformations promote a more rigid and ordered hydration shell, whereas PAM adopts a compact structure with greater chain mobility, resulting in a less ordered hydration layer. Collectively, these findings provide a structure-property framework for the scientifically grounded selection of water-retaining agents. The integrated experimental–computational methodology presented herein establishes a predictive framework for the rational design of functional materials in arid land restoration. Full article

Disposable absorbent hygiene products (AHPs) contain plastics that are challenging to recycle and not biodegradable, making a significant contribution to landfill. Decreasing the nonbiodegradable mass of products could reduce this burden. Despite this, public data on how AHP design and material selection relate to performance is limited. In this work, fifteen commercial AHPs were characterised using dimensional measurement, infrared spectroscopy, and imaging. Simulated urination, air permeability, and moisture management testing were used to assess expected leakage and user comfort. Sustainable materials currently in use were identified, and their performance compared to typical plastics, informing opportunities to replace or reduce nonbiodegradable materials. Polybutylene adipate terephthalate-based leakproof layers replaced polyolefins. Commercial alternatives to polyacrylate superabsorbent polymers (SAPs), with comparable absorption, were not seen. Although absorbency correlated with the mass of absorbants, SAPs reduced surface moisture after absorption and are known for high absorption capacity under pressure, preventing rewetting. Channels and side guards were observed to prevent side leakage and guide fluid distribution, potentially reducing the need for nonbiodegradable nonwoven and absorbant content by promoting efficient use of the full product mass. While synthetic nonwovens typically outperformed cellulosics, apertured and layered nonwovens were associated with improved moisture transport; polylactic acid rivalled typical thermoplastics as a bio-derived, compostable alternative. Although the need for biopolymer-based SAPs and foams remains, it is hoped that these findings will guide AHP design and promote research in sustainable materials. Full article