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Magnetic superabsorbents have been successfully synthesized through aqueous solution polymerization, employing sodium alginate as the backbone material, acrylic acid and acrylamide as the polymeric monomers, Fe3O4 nano-particles as the magnetic component, N,N'-methylenebisacrylamide as the crosslinking agent, and ammonium persulfate serving as the initiator. The micro-morphology and thermal stability of these superabsorbents were thoroughly characterized using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), respectively. A comprehensive investigation was undertaken to examine the swelling capacity, water retention properties, magnetic responsiveness, and reusability of the magnetic superabsorbents. The findings reveal that these superabsorbents possess an impressive maximum water absorption capacity of 302.7 g/g in distilled water. Notably, their swelling ratios maintain high levels within a pH range of 5–10. Featuring a porous structure, the magnetic superabsorbents demonstrate rapid swelling kinetics, attaining swelling equilibrium within 30 min in a 1 wt% NaCl solution. Furthermore, the superabsorbents exhibit excellent magnetic responsiveness, characterized by a maximum saturation magnetization of 7.91 emu/g, allowing for swift separation under an external magnetic field. Lastly, the magnetic superabsorbents display outstanding reusability, with their water absorption capacity in distilled water still exceeding 90% of the initial swelling ratio after seven reuse cycles. [ABSTRACT FROM AUTHOR]

Magnetic superabsorbents have been successfully synthesized through aqueous solution polymerization, employing sodium alginate as the backbone material, acrylic acid and acrylamide as the polymeric monomers, Fe3O4 nano-particles as the magnetic component, N,N'-methylenebisacrylamide as the crosslinking agent, and ammonium persulfate serving as the initiator. The micro-morphology and thermal stability of these superabsorbents were thoroughly characterized using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA), respectively. A comprehensive investigation was undertaken to examine the swelling capacity, water retention properties, magnetic responsiveness, and reusability of the magnetic superabsorbents. The findings reveal that these superabsorbents possess an impressive maximum water absorption capacity of 302.7 g/g in distilled water. Notably, their swelling ratios maintain high levels within a pH range of 5–10. Featuring a porous structure, the magnetic superabsorbents demonstrate rapid swelling kinetics, attaining swelling equilibrium within 30 min in a 1 wt% NaCl solution. Furthermore, the superabsorbents exhibit excellent magnetic responsiveness, characterized by a maximum saturation magnetization of 7.91 emu/g, allowing for swift separation under an external magnetic field. Lastly, the magnetic superabsorbents display outstanding reusability, with their water absorption capacity in distilled water still exceeding 90% of the initial swelling ratio after seven reuse cycles. [ABSTRACT FROM AUTHOR]

Nanogels (Ngl) have emerged as one of the most prominent and convenient systems to act as site-specific drug delivery systems and antimicrobial agents for a varied range of diseases. Super absorbent silver incorporated gelatine-based nanogel (Ngl) grafted with acrylic acid (AAc) (gelatin-grafted-acrylic acid) (SGlAsTC) was synthesized by the chemical polymerization method for use as antimicrobial agents and prospective drug delivery matrices. The nanogel was synthesized employing N, N, Methylene bisacrylamide as a crosslinker and TEMED (N, N, N,N-Tetramethylethylenediamine) as a surfactant. The thus obtained Ngl was characterized by particle size analysis (DLS), FT-R, XRD, EDX, FESEM, and DSC to get evidence of nanogel synthesis. FTIR analysis confirmed the crosslinking reaction with AAc of Ngl, and the spherical morphology studies of SGlAsTC were confirmed by the FESEM image, which showed a sphere-like morphology with porous and crumpled particles. A swelling study was carried out at different pHs (2.2, 4.2, 6.5, 7.4, and 8.2) and at two different temperatures (at 25°C and 37°C) to evaluate the water absorption ability of the synthesized Ngl. The synthesized Ngl was subjected to antimicrobial studies against four different bacteria, exhibiting an exceptional inhibition zone for SGlAsTC against Pseudomonas aeruginosa. Excellent results were observed for SGlAsTC against the bacteria compared to the positive control (azithromycin). The results could be attributed to gelatin molecules that facilitated the absorption of the silver-incorporated AAc chains into the bacterial cell wall and speeded up the destruction of the cell cytoplasm. [ABSTRACT FROM AUTHOR]

The development of new methods to improve the water absorption performance of polymeric materials, taking into account their environmental friendliness, is a promising research direction in Itaconic acid based water‐absorbent polymeric materials. In this study, from the perspective of environmental protection, we propose to design highly absorbent hydrogels with a novel villous‐like structure by using hydrophilic itaconic acid as the raw material and combining it with a novel villous‐like network structure to substantially increase the contact area between the hydrogel and water, thus improving the water absorption rate of the hydrogel. Itaconic acid is water‐soluble and renewable. The widespread use of polymeric water‐absorbent polymers from traditional petroleum sources poses a serious threat to the sustainability of ecosystems, and therefore, itaconic acid has attracted much attention as an alternative to petroleum‐based polymers. The villous‐like network structure is inspired by the villi of the small intestine, the special presence of which expands the absorptive surface area of the small intestine by a factor of about 600, and it is therefore hypothesized that the introduction of this special structure could help the hydrogel to greatly increase the contact area with water and thus achieve the high water absorption properties of the hydrogel. This is also the first time that the villus‐like network structure has been applied to Itaconic acid based hydrogels. The results show that the hydrogel has the property of rapid water absorption and swelling and the water absorption rate of the hydrogel can reach up to 2210 g/g, and the villous‐like structure formed by the hydrogel can be observed in the SEM image. The water‐absorption test of the hydrogel showed that when the molar mass ratio of itaconic acid to acrylic acid was 1:4, the hydrogel absorbed water and swelled rapidly in a short time. The results of the water retention test showed that the hydrogel still existed after 5 days, and the water retention was greater than 86%. In addition, the hydrogel had high reusability, and the water absorption performance of the hydrogel could still reach 89.12% after 6 cycles of the water absorption test. Hydrogel with high water‐absorbing property has good application prospects as fast swelling material in the field of flood control of water conservancy projects. [ABSTRACT FROM AUTHOR]

Innovative superabsorbent hydrogels were synthesized from watermelon rind (WR), an abundant agricultural waste. The process involved free radical polymerization of acrylic acid (AA) and acrylamide (AAm) with WR particles activated by ammonium persulfate (APS), resulting in (AA-co-AAm)/WR hydrogels with high equilibrium swelling capacities of 749 ± 32 g/g. Notably, after eight cycles, the WR hydrogel maintained 94.88 % of its initial swelling capacity, significantly outperforming the (AA-co-AAm) hydrogel without WR (13.80 % retention). This durability, combined with excellent water retention across various soil textures and high adsorption capacity for methylene blue (MB), underscores the WR hydrogel as a superior soil moisture conservation agent. This study marks a significant advance in recycling organic waste and enhancing water management in agricultural soils, demonstrating the potential for sustainable hydrogel development.

Superabsorbent hydrogels are polymers with a 3D network that have attracted the attention of scientists and industrialists because of their fantastic ability to absorb and retain water and aqueous solutions. The most widely used and commercially available superabsorbent hydrogels are synthetic K-acrylate materials. In this novel study, superabsorbent hydrogels have been developed using natural ingredients to have more biodegradable properties. Superabsorbent hydrogels were synthesized from acrylic acid, cassava starch, and chitosan using the γ-irradiation method under different experimental conditions. The γ-irradiation technique was chosen to produce hydrogels free of residues that may remain when chemical crosslinkers are used. The effects of irradiation dose, acrylic acid composition, and the amount of cassava starch and chitosan on the characteristics of produced hydrogels were analyzed. The resulting polymers were further characterized by fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) to evaluate the structure. The thermal behavior of superabsorbent products at different neutralization doses was tested with differential scanning calorimetry (DSC). FTIR data indicated that the grafting reaction was successfully implemented in this work. SEM analysis showed that the hydrogel produced from this study was porous and there was a reduction in pore size with the addition of starch and chitosan. It can be concluded that the addition of cassava starch and chitosan affects the acrylic acid-based superabsorbent properties, which are pore size, thermal behavior, gel content, antibacterial activity, and swelling capacity in water, salt, and urea solutions. The best hydrogel was obtained by adding 0.25 g of cassava starch and 0.25 g of chitosan, using 50 % acrylic acid neutralization and 5 kGy γ-irradiation doses. The graft polymers possess the maximum swelling capacity of 670 g/g for distilled water, 520 g/g for NaCl solution, and 767 g/g for urea solution (relative to the dry weight). These products were sterile from Escherichia coli bacteria and had the potential to be applied as superabsorbent resins for various fields.

The study focus is the valorization of banana agriculture by products by the extraction and derivatization of cellulose and its incorporation in formulations to produce superabsorbent materials endowed with high water absorption performances. The extracted cellulose (BP) was subjected to a controlled oxidation by sodium periodate to convert it to cellulose dialdehyde (DAC) with controlled aldehyde content. The cellulosic materials were incorporated into a suspension containing acrylic acid (AA) and itaconic acid (IA) to produce composite hybrid hydrogels (SA-BP/SA-DAC) by radical chain polymerization in water, using N , N -methylene-bis-acrylamide (MBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The prepared materials were characterized using techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and rheological analysis. Additionally, the absorption and re-swelling capacities of the superabsorbent composites (SAPs) were assessed through kinetic studies in water and NaCl solution. Notably, dialdehyde cellulose (DAC), due to its low crystallinity index, hydrophilicity (attributed to aldehyde and hemiacetal functions), and high polarity, holds promise for enhancing the swelling and water retention capacity of the hydrogel. A water absorption capacity as high as 1240±60 g.g-1 was obtained for SA-DAC with a DAC content of 5 %wt. Additionally, the reusability of the SAPs was evidenced. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel multi-functional superabsorbent polymer (SAP) of carboxymethyl cellulose sodium grafted polyacrylic acid/semi-coke (CMC-g-PAA/SC) was firstly prepared by grafting acrylic acid (AA) onto the carboxymethyl cellulose sodium (CMC) using N,N′-methylene-bis-acrylamide (MBA) as cross-linker, ammonium persulfate (APS) as initiator, and the semi-coke (SC) as inorganic component. The SC is the by-product of coal dry distillation, contains 70% of kaolinite and a certain amount of carbon species and humus, which all have the positive role for the soil and the crop. The FTIR characterization verified that the SAP had been polymerized successfully and the SC incorporated into the polymeric matrix evenly. The SEM revealed that the roughness of the SAP increased significantly with the rise of SC content. The TGA analysis proved that the addition of SC could effectively improve thermal stability. At the same time, the effects of pH sensitive, salt concentration, cation type and reswelling ability on the water absorbency were systematically investigated. The results indicated that the swelling of SAP was insensitive in the wide pH range of in 4–12, and maximum water absorbencies with about 420.8 g/g and 64.8 g/g in distilled water and 0.9 wt% NaCl solution were reached as 10 wt% of SC content introducing. Moreover, the SAP also had the better water retention capacity and reusability whatever the SC content. The effect of salt revealed that cations with higher positive charge gave a more obvious effect for the swelling behavior. In view of the above properties, it can be concluded that CMC-g-PAA/SC may have significant potential for agricultural and horticultural application. [ABSTRACT FROM AUTHOR]

Superabsorbent hydrogels were prepared from biodegradable material, where the matrix was cross-linked cellulose and carboxymethyl cellulose and reinforced by quaternized tunicate cellulose nanocrystals (Q-TCNCs). Due to the large amount of hydrophilic groups on cellulose, carboxymethyl cellulose, and Q-TCNCs, the hydrogels had excellent water absorption capacity. The equilibrium swelling ratio of superabsorbent hydrogels exceeded 500 g/g in deionized water and exceeded 120 g/g even in synthetic urine, which was higher than those of commercial absorbent materials composed of copolymers of acrylic acid and acrylamide. The water absorption performances and mechanical properties of the hydrogels could be adjusted by changing the content of Q-TCNCs. The resultant materials were expected to replace those polyolefin-based materials, thereby reducing environmental pollution. [ABSTRACT FROM AUTHOR]

In this paper, agar/gelatin and acrylic acid-co-vinyl acetate (monomer chains) based superabsorbent, fabricated using gamma radiations as an initiator and N-N′ dimethylene bisacrylamide as a crosslinker, has been investigated for its swelling behaviour (Max. Ps = 8010) in distilled water as a function of time, temperature and pH. The hydrogel has further been applied for sustained delivery of diethyl carbamazine citrate under three pH conditions at 37 °C. It has been found to show non-Fickian type mechanism as the drug release showed diffusion coefficient less than 0.50 for all the pH conditions. The gel characteristic constant 'n' was found to be: 0.910 at 9.2 pH, 0.832 at 7.0 pH and 0.768 at 2.2 pH with their corresponding 'k': 0.175, 0.242 and 0.413, respectively. The initial diffusion coefficient has been found to show greater values than late diffusion coefficient confirming greater release at the early stages of the drug release than that in the late stages. Also to apply BGCP in soil treatment its moisture retention capacity has been studied using three different soil models. BGCP was found to retain moisture under clay, mix and sand soil models for 57 days, 42 days and 32 days, respectively. Under bio-composting method of biodegradation sample was found to be 91% degraded after 70 days. [ABSTRACT FROM AUTHOR]

Superabsorbent polymers (SAPs) are a kind of materials which are widely used in many fields where the absorption of various aqueous solutions is prime importance. Given the fact that a great number of SAPs available on the global market are made from the poorly degradable and expensive materials, recently, there has been increasing interest in looking for low-cost and environmental friendly solutions in SAP production industry. In this study, three types of hybrid SAPs composites were synthesized through the graft polymerization of acrylic acid (AA) into three kinds of natural polysaccharides backbone chain, separately, which are: Hydroxyethyl cellulose (HEC), Xyloglucan (XG), and Guar gum (GG) in an aqueous solution, with ammonium persulfate (APS) as the initiator, N,Nʹ-methylenebisacrylamide (MBA) as the cross-linker, and diatomite clay as an inorganic nano-filler. The FTIR and SEM characterization results suggested that three kinds of hybrid SAP composites were successfully synthesized with high porosity on the surface. The study about the capacity of water absorbent revealed that the optimized swelling ratios of the three superabsorbent composites (HEC-g-PAA/diatomite, XG-g-PAA/diatomite, and GG-g-PAA/diatomite) are 1174.85 g · g - 1 , 1057.06 g · g - 1 , and 692.83 g · g - 1 , respectively. In addition, the effect of each parameter such as polysaccharide species and the content of polysaccharide, initiator, cross-linker, diatomite and the degree of neutralization toward the water absorbency capacity of the obtained SAP were determined and discussed. [ABSTRACT FROM AUTHOR]

In this work, a novel environmentally friendly semi-interpenetrating anionic hydrogel based on Xanthan gum/cross-linked polyacrylic acid/graphene oxide was prepared as superabsorbent for removing methylene blue as cationic dye from the water. Acrylic acid (AA) was crosslinked in xanthan (XG)/graphene oxide (GO) solution by a novel synthetic acrylic-urethane crosslinker (MS). Various analyses such as SEM, FT-IR, 1H NMR, XRD, and TGA were used to study morphology, structure, and thermal stability of MS and semi-IPNs. The synthesized hydrogels showed pH-sensitive behavior in water uptake, with the highest and lowest swelling in alkaline and acidic media, respectively. The nanocomposites had better dimension stability and dye adsorption with increasing GO from 0 to 1%. Hydrogel containing 1% GO showed 485% and 88.5% swelling and dye adsorption efficiency, respectively. Different kinetic models including 1st order, 2nd order, intra-particle diffusion, and Elovich kinetics were studied. All models except 2nd order model are in good agreement with the experimental data. GO-containing hydrogels had a significant effect on methylene blue adsorption and this effect increased with an increase in the amount of GO. PAA/XG/GO hydrogels can be introduced as an eco-friendly adsorbent with high efficiency for the removal of cationic dye pollutions. Unlabelled Image [ABSTRACT FROM AUTHOR]

Hydroxyethylcellulose (HEC) is a biocompatible, biodegradable, nontoxic, hydrophilic, non- ionic water soluble derivative of cellulose. It is broadly used in biomedical field, paint industry, as a soil amendment in agriculture, coal dewatering, cosmetics, absorbent pads, wastewater treatment and gel electrolyte membranes. Industrial uses of HEC can be extended by the its grafting with different polymers including poly acrylic acid, polyacrylamide, polylactic acid, polyethyleneglycol, polydimethyleamide, polycaprolactone, polylactic acid and dimethylamino ethylmethacrylate. This permits the formation of new biomaterials with improved properties and versatile applications. In this article, a comprehensive overview of graft copolymers of HEC with other polymers/compounds and their applications in drug delivery, stimuli sensitive hydrogels, super absorbents, personal hygiene products and coal dewatering is presented. • Hydroxyethylcellulose (HEC), non-ionic water soluble derivative of cellulose, broadly used in various industries • Grafting of HEC with different polymers enhances its utilization in industry. • HEC supports the formation of new biomaterials with improved properties and applications [ABSTRACT FROM AUTHOR]

In this study, acrylic acid (AA) and cellulose nanofibers (CNFs) were used as main materials to synthesize an acrylic-nanocellulose hybrid hydrogel nanocomposite in the presence of urea. The interpenetrating polymer networks were obtained by radical polymerization in different urea: AA ratios (0:10, 1:10, 3:10, 5:10, 10:10). Fourier transform infrared spectroscopy (FTIR) combined with X-ray diffraction (XRD) and elemental analysis techniques confirmed the chemical interaction of urea in the network structure. Free absorption and water absorption under load (AUL) of the synthesized hydrogels varying in urea: acrylic acid weight ratios were measured in distilled water and saline (0.9 wt%) solution for hybrid (5 wt% CNFs) and pure polyacrylic acid (0 wt% CNFs) hydrogels. It was found that incorporation of urea and CNFs in the hybrid structure generating compact hydrogel networks with high crosslink density leading to lower absorption with and without pressure, whereas incorporation of urea in the structure resulted in a more extended network with higher absorption capacity (about 3×) than hybrid structure. [ABSTRACT FROM AUTHOR]

The mechanical strength of superabsorbents is an important practical factor that can be characterized by measuring the absorbency of the superabsorbent under load. In the last decades, many efforts have been devoted to enhancing the mechanical strength of superabsorbents. Herein, as an attempt to increase the superabsorbent mechanical strength, two types of star-shaped bio-based modifiers were designed and synthesized via condensation reaction between acids and alcohols. The chemical structures of the bio-based modifiers were characterized via FT-IR and 1H NMR analysis. Glycerin, lactic acid, succinic acid, and itaconic acid used for the synthesis of the star-shaped modifier, which further used in different ratios in the bulk of the superabsorbent. Moreover, another modifier was synthesized from glycerin, lactic acid, and methacrylic anhydride, and successfully used as a surface modifier for superabsorbents in different ratios. The absorption analysis showed that the employment of the optimum amount of the bulk modifier (4.75 wt.%) increases the AUL almost 4 units, without significant impacts on the water and NaCl solution absorbencies. Also, the incorporation of the optimum amount of the surface modifier increases the AUL about 3 units. As a result, the AUL value of the acrylic acid- sodium acrylate superabsorbent enhanced ~7 units by the incorporation of these bio-based modifiers-from 17.3 for the pristine superabsorbent to 24.2. [ABSTRACT FROM AUTHOR]

During the past decades, production and applications of petroleum-based superabsorbents have grown dramatically; currently, superabsorbents are produced from acrylic acid, which consequently increase the environmental concerns. The high consumption rate of superabsorbent on the one hand, and their persistence in the environment from the other hand would make the waste of this material a potential hazard for the environment. These materials are not biodegradable, and if degraded hazardous derivatives would be released into soil and water. The current work presents the synthesis and the performance of a novel superabsorbent hydrogel, based on star-shaped bio-based compartments and acrylic acid. Herein, the synthesis of two bio-based star-shaped monomers will be reported based on the condensation reaction between hydroxyl and carboxylic acid end groups of a bio-acid and a bio-alcohol. The first monomer was synthesized from glycerin, succinic acid, lactic acid, itaconic acid, and acrylic acid. The second monomer was synthesized from glycerin, lactic acid, and methacrylic acid. The monomers structures were characterized via FT-IR and 1HNMR spectroscopies. The different portions of biobased monomers (10, 30, 50, and 70 wt%) were used in combination with the acrylic acid monomer to form hybrid superabsorbents. The swelling properties and the absorbency under load (AUL) of superabsorbents were investigated in turn. The maximum absorption capacities (398.49 and 90.10 g g−1 in water and saline solution, respectively) were observed when 30 wt% of acrylic acid backbone of the superabsorbent was replaced with the bio-based monomer. Moreover, economic and environmental profiles of the hybrid SAPs have been evaluated. The comparative environmental assessment performed using life cycle analysis method, based on the material and energy balances obtained from the available literature. While the economy of the hybrid SAPs production still suffers from the high price of the employed raw biomaterials during manufacturing, the better environmental profiles obtained for the hybrid SAPs. [ABSTRACT FROM AUTHOR]

Most commercially available hydrogels have a low surface to volume ratio due to the spherical or pseudo-spherical geometry, which highly affects the corresponding swelling properties of the hydrogels. In this study, a nanofibrous superabsorbent were prepared using the gas-assisted electrospinning of Poly(acrylic acid) (PAA). The morphology of the nanofibrous hydrogel and its effect on the swelling performance were investigated. For this purpose, different concentrations of PAA solutions, operating conditions for the gas-assisted electrospinning technique, as well as cross-linking agent (1,4-butanediol diglycidyl ether) were studied. Moreover, sodium hydroxide (NaOH) was used to neutralize the PAA solutions in different contents. Fourier-transform infrared spectroscopy was used to investigate the hydrogel structure and the chemical cross-linking reaction. The scanning electron microscopy (SEM) was used to investigate the fibers morphology. SEM results confirmed the nanofiber formation using the gas-assisted electrospinning in this work. Free absorption, absorption under load, and the dynamic mechanical properties behavior of the specimens were investigated, demonstrating that the specimen prepared using 9 wt% PAA, 30% neutralized by NaOH solution, electrospun at 20 μL/min, and cross-linked by 1,4-butanediol diglycidyl ether had the highest swelling ratio, up to 90,000% and 30,000% for distillated water and standard NaCl solution, respectively. [ABSTRACT FROM AUTHOR]

A series of superabsorbent hydrogels were synthesized from partially neutralized acrylic acid with varying degree of neutralization (0-1) using gamma radiation. The effects of degree neutralization of acrylic acid on swelling ratio were studied. DSC measurement was performed to understand the type of end products resulting from irradiation. The morphologies of the hydrogels were examined using SEM. The chemical changes of the hydrogels were characterized using FTIR. At optimum conditions (10 kGy, 15 min), the hydrogels with neutralization degree 0.5 exhibited rapid swelling with the highest swelling ratio ~1000 g/g. The results of DSC studies confirmed the possible formation of the type hydrogels from irradiated partially neutralized acrylic acid, and the hydrogels showed large numbers of pores from SEM examination.

Starch was extracted from Sorghum bicolor grains by alkali steeping method and was utilized for the production of absorbent material by grafting and crosslinking with binary mixtures of vinyl monomers viz. acrylic acid and acrylamide. Both unmodified and modified starches were characterized with Thermogravimetric analysis, Infra-Red spectroscopy, Scanning electron microscopy and X-ray diffraction analysis, to ascertain the modification of the starch. The parameters of the reaction system viz. initiator concentration, monomer concentration, starch to monomer ratio, etc. were optimized. The modified starch showed enhanced water absorption in the range of 49-85 g/g. Absorbency of the products increased after treatment with aqueous alkali solution due to saponification at higher temperature. The saponified products showed increased water absorption level in the range of 245-400 g/g. The product thus obtained using optimized condition of grafting, on saponification found to be highly superabsorbent displaying the water absorbency of 400 g/g. The influence of pH on absorption of water was also tested and best results were obtained at pH 7-8. [ABSTRACT FROM AUTHOR]

Fast swelling hydrogels were synthesized from the mixture of acrylamide (AAM)-acrylic acid (AA)-starch (15:5:1 w/v) solution by radiation crosslinking with varying irradiation doses (7.5-12.5 kGy) at room temperature. The copolymers were characterizated by Fourier transform infra red spectroscopy (FTIR) and Differential scanning calorimetry (DSC). It was found that hydrogels showed superabsorbent properties with higher swelling capacities (~400 g/g) and reached at a very short time (3 min). There was no significance difference between the effect irradiation dose on swelling of hydrogels. The hydrogels were also found to sensitive to the ionic strength of medium. The FTIR spectra and thermogram DSC of hydrogels were confirmed the crosslinking occurs in the hydrogels.

Hydroxyethylcellulose (HEC)/acrylic acid (AAc) copolymer gels with superabsorbent properties were synthesized from aqueous solutions by radiation-initiated crosslinking. The effect of the acrylic acid content on gel properties was determined at different synthesis conditions. The partial replacement of the cellulose derivative with acrylic acid improved the gelation, leading to higher gel fraction and lower water uptake even in very low concentrations (1–5%). In the presence of acrylic acid lower dose and solute concentration was required for the gel synthesis. The molecular properties of the hydroxyethylcellulose also had a major effect on the gelation: higher molecular mass resulted in better gel properties. The acrylic acid also affected the electrolyte sensitivity of the hydrogels: while pure HEC gels were unaffected by the ionic strength of the solvent, the water uptake of HEC/AAc gels decreased with the salt concentration. The sensitivity also depended on the acrylic acid ratio. [ABSTRACT FROM AUTHOR]

PVA/P(AA-AM) super absorbent polymer was prepared with polyvinyl alcohol (PVA), acrylic acid (AA) and acrylamide (AM) as main materials by solution polymerization. The morphologies and composite physical states were investigated using fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetry analysis (TG-DTG). Scanning electron microscopy observations revealed that a large number of porous network structures existed in the resin. Results from FTIR and XRD suggested that PVA/P(AA-AM) superabsorbent which had semi-interpenetrating network structure had been successfully prepared. Results from TG-DTG suggested that PVA/P(AA-AM) superabsorbent had good thermal stability under 200°C. At the same time it had good water retention property and the water retention property of sandy soil was improved obviously when the resin was added into the sandy soil. [ABSTRACT FROM PUBLISHER]

Modification of poly (acrylamide-co-acrylic acid) superabsorbent hydrogels with varying starch concentration (1-3%) via simultaneous gamma radiation have been carried out. The structure and morphology of copolymers were characterization by Fourier transform infra red spectroscopy and scanning electron microscopy. The gel fraction, swelling kinetics and the equilibrium degree of swelling (EDS) of the hydrogels were studied. It was found that the an increase in the starch content present in the hydrogels (1-3%) and with increase irradiation dose from 10 kGy up to 30 kGy, the swelling ratio decreased from 250-100 g/g. Incorporation of 1% starch increases the EDS of the hydrogels up 350 g/g. Under maximum conditions, poly(AAm-co-AA)-starch hydrogels with high gel fraction (~93%) was prepared from aqueous solution containing 5% AAm, 15% acrylic acid and 0-3% starch. The hydrogels were sensitive against salts solution.

Acrylic acid (AA) monomer was directly grafted onto chitosan using ammonium persulfate (APS) as an initiator and methylenebisacrylamide (MBA) as a crosslinking agent under an inert atmosphere. Two factors affecting the swelling capacity of the obtained hydrogel, AA and MBA concentrations, were studied. The polymer structures were characterized by FTIR spectroscopy. Maximum water absorbency of the optimized final product was found to be 434 gr/gr. Also, I studed manner swelling of product in different solution salty. results shown that the swelling capacity decreased with increasing of ionic strength. Farthermore, the swelling of superabsorbant hydrogel was measured in various Solutions with PH values ranging from 1 to 12. the hydrogels exhibited the highest swelling at PH 3 and8. also the swelling kinetics in distilled water investigated.

Lignosulfonate- g -acrylic acid (LS- g -AA) hydrogels that possess superabsorbent capacity were synthesized by grafting acrylic acid (AA) on the backbone of lignosulfonate (LS) in the presence of N , N ′-methylene- bis -acrylamide (MBA) as initiated by laccase/ t -BHP(tert-butyl hydroperoxide). Specifically, the carboxylic acid groups introduced by grafting acrylic acid, significantly enhanced the absorption capacity of LS- g -AA hydrogels. In this case, methylene blue (MB) was the representative dye substrate to study absorption dynamics. It was found that the equilibrium absorption of MB reached 2013 mg·g − 1 while pH, absorption time, and initial MB concentration affected the overall absorption capacity. The absorption isotherms and kinetics obeyed standard Freundlich and pseudo-2nd-order models, respectively. Furthermore, preliminary desorption experiments were conducted in weak acid solution and showed that ~ 50% of the original MB could be removed over one rinse cycle. [ABSTRACT FROM AUTHOR]

Superabsorbent polymers fabricated via grafting polymerization of acrylic acid from chitosan (CTS) yields materials that suffer from poor mechanical strength. Hybridization of chitosan with cellulose (Cell) via chemical bonding using thiourea formaldehyde resin increases the flexibility of the produced hybrid (CTS/Cell). The hybridization process and post graft polymerization of acrylic acid was followed using Fourier transform infrared (FTIR). Also, the obtained structures were homogeneous and exhibited uniform surface as could be shown from imaging with scanning electron microscopy (SEM). Thus, the polymers derived from the grafting of polyacrylic acid from (CTS/Cell) gave rise to much more mechanically robust structures ((CTS/Cell)-g-PAA) that bear wide range of pH response due to presence of chitosan and polyacrylic acid in one homogeneous entity. Additionally, the obtained structures possessed greater water absorbency 390, 39.5 g/g in distilled water and saline (0.9 wt.% NaCl solution), respectively, and enhanced retention potential even at elevated temperatures as revealed by thermogravimetric analysis (TGA). This could be explained by the high grafting efficiency (GE%), 86.4%, and grafting yield (GY%), 750%. The new superabsorbent polymers proved to be very efficient devices for controlled release of fertilizers into the soil which expands their use in agriculture and horticultural applications. [ABSTRACT FROM AUTHOR]

Superabsorbent hydrogels were prepared by gamma irradiation from aqueous solutions of carboxymethylcellulose (CMC) and acrylic acid (AAc) with varying CMC:AAc ratio. By partially replacing the CMC with AAc the gelation increased and led to a higher gel fraction and lower water uptake. Moreover, the gelation required significantly milder synthesis conditions. Decreasing both the dose and the solute concentration in the presence of AAc led to gels with higher gel fraction and higher degree of swelling compared to pure CMC gels. Increasing the AAc content up to 10% proved to be very effective, while very high AAc content (over 50%) hindered the gelation process. [ABSTRACT FROM AUTHOR]

Dye removal from wastewater via adsorption constitutes an active area of research in effluent treatment. For this purpose, superadsorbent hydrogels have emerged as a promising tool; however, large adsorption capacities for various dyes are still required. As a novel adsorbent, lignin is attracting attention owing to its abundant sources and environmental friendliness; unfortunately, its hydrophobicity limits its practical application. Herein, lignin was directly esterified using methacrylate anhydride, itaconic anhydride, or maleic anhydride to produce three lignin esters (LEs) with different hydrophilic properties. These LEs were subsequently used to copolymerize with acrylic acid, yielding three types of hydrogels. Because of high water-absorbing capacity of hydrogels, the highest adsorption capacity reported to date for methylene blue was obtained (2445 mg g−1) using lignin-based adsorbents. The type of LEs, the reactant concentrations and ratios, and the pH of the soaking solution affected the properties and hence the adsorption capacities of the hydrogels. The adsorption process was fitted with a pseudo-second-order model and the Langmuir adsorption isotherm model. This study reveals the synergistic adsorptive action of lignin and confirms the potential of LE–acrylic acid hydrogels for removing methylene blue from sewage. • Three kinds of lignin esters (LEs) containing double bonds were synthesized • LEs-based hydrogels were prepared via copolymerization using acrylic acid as monomer. • The hydrogels exhibited excellent methylene blue removal performance (2445 mg g−1). • The lignin esters improved the formation of porous structure and adsorption capacity. • The lignin esters introduced multi-interactions among the hydrogels and dye molecules. [ABSTRACT FROM AUTHOR]

A novel wheat straw-composite superabsorbent with high gel strength and high water absorbency was prepared by graft polymerization with acrylic acid, acrylamide and maleic anhydride-modified wheat straw, using N,N-methylene-bis-acrylamide as a crosslinker and ammonium persulfate and sodium bisulfite as redox initiators. Factors influencing water absorbency and gel strength of the superabsorbent composite, such as amount of maleic anhydride-modified wheat straw, crosslinker amount and initiator amount, were investigated. Morphologies and structure of the wheat straw-composite superabsorbent were characterized by Fourier transform infrared spectroscopy, scanning electron microscope and X-ray diffraction. Composite superabsorbent with modified wheat straw as high as 25 wt% still has water absorbency of 435 g/g. Fourier transform infrared spectroscopy spectra indicate the structure of wheat straw graft copolymer. Scanning electron microscope data show that the discontinuous sheet structures of wheat straw disappear and gel aggregates with many large microporous holes and small capillary pores are formed after wheat straw graft modification. The wheat straw-composite superabsorbent has better thermal stability than those of raw wheat straw and maleic anhydride-modified wheat straw. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Cassava starch grafted with acrylic acid shows superabsorbent properties. [•] More than half of the absorbed water is retained under severe suction. [•] A mathematical analysis was made to assess the mechanisms of water absorption. [•] Polymer chain relaxations are the governing factor at the most important conditions. [ABSTRACT FROM AUTHOR]

A novel corn stalk-composite superabsorbent was prepared by graft copolymerization of corn stalk with acrylic acid, acrylamide and sodium 4-styrenesulfonate in aqueous solutions after the pretreatment of corn stalk, using N,N-methylenebisacrylamide as a crosslinker and ammonium persulfate and sodium bisulfite as redox initiators. Factors affecting water absorption rate of the superabsorbent composite, such as the amount of corn stalk, crosslinker, and initiator were investigated. Adsorption rates of Ni(II) and Cd(II) ions of the corn stalk-composite superabsorbent were also studied. Corn stalk-composite superabsorbent had equilibrium adsorption capacities of 210 mg g within 50 min and 505 mg g within 150 min for Ni(II) and Cd(II) ions, respectively. Fourier transform infrared spectroscopy indicated the structure of corn stalk-composite superabsorbent. X-ray diffraction indicated that the sharp diffraction peaks of corn stalks disappeared and transformed into a large and wide amorphous dispersion peak. The discontinuous sheet structure of corn stalks disappeared and gel aggregates with microporous holes and small capillary pores were formed after corn stalk graft modification. After absorbing water, the swollen composite superabsorbent formed a network-like structure filled with water. Thermal gravimetric analysis indicated that the composite superabsorbent had high thermal stability with three step degradations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Maleylated cotton stalk cellulose (MCSC) was synthesized and as a crosslinker. [•] MCSC-g-PAA superabsorbent was prepared by UV photopolymerization. [•] The effects of various factors on the water absorbency and monomer conversion were investigated. [•] The structure and properties of the superabsorbent materials were evaluated. [•] The obtained superabsorbent was easily degraded by cellulose. [ABSTRACT FROM AUTHOR]

New water harvesting bentonite clay reinforced modified cellulosic/Acrylic Acid hydrogel composite has been developed The samples have been characterized by spectroscopic analysis (FTIR and 13C –NMR), morphology (SEM and EDX), flow behavior (Rheology), swelling and absorption properties under different environmental conditions like temperature, pH and presence or absence of ionic solutions. The prospects of these novel superabsorbent hydrogels have been explored for the growth and survival of plants, particularly in the semi-arid region for its superabsorbency and high retention capacity. Hydrogel with 5 wt % clay exhibits maximum swelling percentage, 19040% within 26 min of swelling time at a temperature of 25 °C and 36600% absorbency once it reaches the equilibrium swelling after a week. Brassica juncea seedlings are allowed to grow in black soil mixed with this cellulosic biocompatible superabsorbent hydrogels. A close observation of three weeks with different programmed watering schedule, simulating the drought situation of the semi-arid region is also reported here. A significant extent of survival and growth of the plant is noted even during the period of reduced watering for the gel-soil mixture. [Display omitted] • Michael Addition reaction is successfully used to modify cellulose. • Bentonite incorporation significantly improves rheological characteristics of gel. • Water absorbency reaches to 36600%. • Gel is found to reduce water requirement for the growth and survival of plants. [ABSTRACT FROM AUTHOR]

A new konjac glucomannan (KGM)-based superabsorbent polymer, KGM- g-poly(acrylic acid- co-acrylamide), was prepared by the free radical grafting solution polymerization of acrylic acid (AA) and acrylamide (AM) monomers onto KGM in the presence of N, N′-methylenebisacrylamide as a crosslinker with potassium persulfate as an initiator. The effects of reaction parameters, including the amount of crosslinking agent and initiator, the weight ratio of both (AA + AM) to KGM and AM to (AA + AM), neutralization degree of AA, bath temperature, and reaction time, on the water absorbency of the superabsorbent were investigated. The Fourier transform infrared spectroscopy was used to characterize the structures of the copolymer. The maximum water absorbency of the optimized product was 650 g/g for distilled water and 70 g/g for a 0.9 wt % aqueous NaCl solution. Furthermore, the water retention of the copolymer in soils was studied. The effect of the copolymers on the aggregate distribution of soils was also evaluated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Superabsorbent polymers (SAPs) based on acrylic acid (AA), sodium acrylate (SA), and acrylamide (AM) were synthesized by inverse suspension polymerization using ethylene glycol dimethacrylate as the crosslinking agent. The equilibrium swelling capacities and the rates of swelling of SAPs varied with the AM content and followed first-order kinetics. The photodegradation of SAPs in their equilibrium swollen state was carried out by monitoring their swelling capacity and the residual weight fraction. The SAPs degraded in two stages, wherein the swelling capacity increased to a maximum and then subsequently decreased. Thermogravimetric analysis of the SAPs indicated that the copolymeric superabsorbents had intermediate thermal stability between the homopolymeric superabsorbents. The activation energies of SAPs with 0, 20, and 100 mol % AM content were determined by Kissinger method and were found to be 299, 248, and 147 kJ mol−1, respectively. The ultrasonic degradation of the superabsorbents was carried out in their equilibrium swollen state, and the change in the viscosity with ultrasonication time was used to quantify the degradation. The ultrasonic degradation of AA/SA superabsorbent was also investigated at various ultrasound intensities. The degradation rate coefficients were found to increase with the intensity of ultrasound. The ultrasonic degradation of AA/SA/AM (20% AM) was also carried out, and degradation rate was found to be more than that of the AA/SA superabsorbent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Abstract: Recently enhance oil recovery (EOR) technology is getting more attention by many countries since energy crises are getting worse and frightened. One of the reasons for this is due to the shortage of current oil resources and difficulties in finding a new oil field. Indonesia is one of the examples, before 2004 Indonesia is a net oil exporting country but after that Indonesia is a net oil importing country. The oil demand in the country is increasing while the oil production capacity is decreasing. In fact, when a new oil reservoir is drilled, the oil amount obtained from it is about 20-40% of the potential and hence there is still 60-80% oil left in the reservoir. Application of EOR technology gives an additional chance to get out more oil from the reservoir, possibly about another 20%. Polymer is the material that plays an important role in the application of EOR technology, especially surfactant and hydrogel polymers. In the technology, surfactant polymer is injected to the reservoir to reduce an interfacial tension between oil and water and is able to wipe out the trapped oil from the reservoir rock and hence increase the oil production. While an injection of hydrogel polymer to the reservoir is to increase a viscosity of fluid containing water so that the fluid is more difficult to flow than the oil, and as a result, the oil production increases. The most common polymer used for this application is polyacrylamide group. [Copyright &y& Elsevier]

In this paper, the intercalated organic-montmorillonite (OMMT) was prepared by the cation exchange reaction, using N,N’-dimethyl-N-dodeoyl methacryloxylethyl ammonium bromide (DMAEA-DB) as an intercalation agent, which contain vinyl group. Then a novel poly (acrylic acid-co-acrylamide)/OMMT nanocomposite superabsorbent was synthesized by inverse suspension polymerization. The superabsorbent hydrogels prepared were characterized by X-ray diffraction (XRD) and FT-IR Spectrometer (FTIR). The effect of polymerization variables, including the amount of OMMT, cross-linker, initiator, acrylic acid (AA), and neutralization degree of AA, on water absorbency were investigate. Results showed that the intercalation was successful. OMMT dispersed in polymer molecules on a nanoscale after copolymerization. The water absorbency of the nanocomposite was much higher than that of the pure P(AA-AM). The highest absorbencies of nanocomposites for deionized water and saline water (0.9%) were 1100 mL/g and 87.5 mL/g, respectively. [ABSTRACT FROM PUBLISHER]

Nanocomposite superabsorbents were synthesized by graft copolymerization of mixture of acrylamide (AAm) and acrylic acid (AA) onto collagen using potassium persulfate (KPS) as a free radical initiator and methylenebisacrylamide (MBA) as a crosslinker. Nanoclay sodium montmorillonite (MMt) was introduced as filler into superabsorbent. The chemical structure of the Collagen-g-poly(Sodium Acrylate-co-Acrylamide)/MMt nanocomposite was characterized by means of FTIR spectroscopy, XRD patterns, and TGA thermal methods. Morphology of the sample was examined by scanning electron microscopy (SEM). The effects of reaction variables were systematically optimized to achieve a superabsorbent with swelling capacity as high as possible. Under the optimized conditions concluded, the maximum swelling capacity in distilled water was 950 g/g. Dewatering of nanocomposite and clay-free superabsorbent revealed that inclusion of nanoclay into superabsorbents can improve water retention of superabsorbent under heating. The swelling ratio in various salt solution and kinetic of dewatering was also determined and additionally, the swelling of nanocomposite superabsorbent was measured in solution with pH ranged 1-13. The synthesized nanocomposite exhibited a pH-responsive characteristic. [ABSTRACT FROM AUTHOR]

In current study, a series of novel guar gum- graft-poly(sodium acrylate- co-styrene)/attapulgite (GG- g-P(NaA- co-St)/APT) superabsorbent nanocomposites were prepared by the simultaneous graft copolymerization of partially neutralized acrylic acid (NaA), styrene (St) and attapulgite (APT) onto natural guar gum (GG), using ammonium persulfate (APS) as the initiator and N,N'-methylene- bis-acrylamide (MBA) as the crosslinking agent. Fourier Transform Infrared (FTIR) and ultravoilet (UV) spectra confirmed that NaA and St had been grafted onto GG backbones and APT participated in the polymerization reaction. The incorporation of St and APT clearly improved the surface porous morphology of the composites as exhibited by Filed Emission Scanning Electron Microscopy (FESEM). The effect of St and APT on the swelling properties and the swelling kinetics of the developed nanocomposite was investigated. Results showed that the simultaneous incorporation of proper amount of hydrophobic co-monomer St and inorganic nano-scale APT not only obviously enhanced the swelling capacity but highly improved the swelling rate, and the nanocomposite showed better salt-resistant capability and excellent pH-stability in various pH solutions. [ABSTRACT FROM AUTHOR]

To improve the utilization of fertilizer and water resources at the same time, a new slow-release PK compound fertilizer (SRCF) with the function of water retention was prepared. Element analysis results showed that the product contained 20.46% potassium (shown by K2O) and 15.45% phosphorus (shown by P2O5), which were trapped in the matrix of carboxymethylcellulose-graft-poly(acrylic acid-co-itaconic acid) superabsorbent polymer. Major factors affecting the water absorbency of SRCF such as weight ratio of itaconic acid (IA) to acrylic acid (AA), contents of crosslinker, K2HPO4, and carboxymethylcellulose (CMC) were investigated and optimized. The water absorbency of the product was 130 times its own weight if it was allowed to swell in tap water at room temperature for 1 h. Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric/Differential thermal analysis (TG/DTA) confirmed that AA and IA monomers were graft-copolymerized onto CMC backbone and presented the improved thermal stability. The water evaporation of the fertilizer-containing superabsorbents, as well as their nutrients release in sandy soil was carried out, and a possible slow-release mechanism was proposed. Additionally, compressive modulus measurements revealed that the introduction of CMC could improve the mechanical properties of the superabsorbents. These studies showed that the product with good slow-release and water retention properties, being economical and environment-friendly, could be expected to have wide potential applications in modern agriculture and horticulture. [ABSTRACT FROM AUTHOR]

This article reports the cointercalation of acrylic acid (AA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) in the interlayer region of MgAl layered double hydroxide (LDH) and the application of this inorganic-organic composite material in the field of water superabsorbent. The monomers of AA and AMPS were cointercalated into galleries of MgAl−LDH (denoted as AA−AMPS/LDH) with various molar ratios by ion-exchange method, which was confirmed by powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), and elemental analysis. The polymer-based superabsorbent was prepared through in situ free-radical aqueous copolymerization of AA and AMPS, with AA−AMPS/LDH as additive, N,N′-methylenebisacrylamide (NMBA) as crosslinker and potassium persulfate (KPS) as initiator. The composition of this poly(AA-co-AMPS)/LDH was demonstrated as a good water superabsorbent. The LDH content, water absorbency, thermal stability, and swelling rate of this superabsorbent were also investigated in detail. Results showed that the incorporation of a 5 wt % AA−AMPS/LDH into polymer matrix increased its water absorbency significantly by 27.7% (in water) and by 51.5% (in 0.9 wt % NaCl solution). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

Abstract: A system for incorporating antimicrobial zinc into polymeric materials, in particular hydrogel type polymers has been developed. Zn(Bipy-(MMOES)2) a zinc carboxylate monomer was designed with the purpose of mimicking commercial cross linking agents such as ethylene glycol diacrylate, as well as containing antimicrobial zinc ions (Zn2+), with the intention that it can be used to cross link into any polymeric material, the example here being polyacrylic acid. Two systems were studied: a homopolymer of the Zn(Bipy-(MMOES)2) and copolymers of Zn(Bipy-(MMOES)2) with acrylic acid (AA). The AA – Zn(Bipy-(MMOES)2) produced water swellable polymers which retained antimicrobial activity. The ability of the polymers to release the zinc ions was shown to be pH responsive and the leachate analysed to give a proposed mechanism of action. The Zn(Bipy-(MMOES)2) monomer and polymers have shown antibacterial activity against both gram positive Methicillin susceptible staphylococcus aureus (MSSA 476) and gram negative Pseudomonas aeruginosa (PA01). [Copyright &y& Elsevier]

Free-radical graft copolymerization among sodium carboxymethylcellulose (CMC), partially neutralized acrylic acid (NaA), medical stone (MS) and crosslinker N,N!-methylene-bis-acrylamide (MBA) was performed to prepare new carboxymethylcellulose- g-poly(sodium acrylate)/medical stone (CMC-g-PNaA/MS) superabsorbent composites. Fouriertransform infrared (FTIR) spectra, thermogravimetry- differential scanning calorimetry (TG-DSC) and field emission scanning electromicrsocopic (FESEM) analysis confirmed that NaA had been grafted onto CMC backbone and MS participated in polymerization, and the thermal stability and surface morphologies were improved by the addition of MS. Energy dispersive spectrometer (EDS) and elemental map (EM) analyses revealed the better distribution of MS in the CMC-g-PNaA matrix. The incorporation of 20 wt% MS clearly enhanced the water absorption by 100% (from 317 to 634 g/g). The developed composites showed enhanced swelling rate and On-Off switching swelling characteristics in various pH solutions, saline solutions and hydrophilic organic solvents, which represented interesting and reversible pH-, saline- and hydrophilic organic solvent-responsive characteristics. In addition, the composite exhibited intriguing time-dependent kinetic swelling properties in various heavy metal solutions. [ABSTRACT FROM AUTHOR]

A series of granulated semi-interpenetrating polymer network (semi-IPN) superabsorbent hydrogels composed of chitosan- g-poly(acrylic acid) (CTS- g-PAA) and poly(vinyl alcohol) (PVA) were prepared by solution polymerization using ammonium persulfate (APS) as an initiator and N, N′-methylenebisacrylamide (MBA) as a crosslinker. The effects of reaction conditions such as the concentration of MBA, the weight ratio of AA to CTS, and the content of PVA on water absorbency were investigated. Infrared (IR) spectra and differential scanning calorimetry (DSC) analyses confirmed that AA had been grafted onto CTS backbone, and PVA semi-interpenetrating into CTS- g-PAA networks. SEM analyses indicated that CTS- g-PAA/PVA has improved porous surface and PVA was uniformly dispersed in CTS- g-PAA network. The semi-IPN hydrogel containing 10 wt% PVA shows the highest water absorbency of 353 and 53 g g in distilled water and 0.9 wt% NaCl solution, respectively. Swelling behaviors revealed that the introduction of PVA could improve the swelling rate and enhance the pH stability of the superabsorbent hydrogel. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Superabsorbent resin was synthesized based on poly(ethylene glycol) methacrylate (PEGMA), acrylic acid(AA) and acrylamide(AM) by inverse suspension polymerization. By plenty of trial and error in previous works, we used mono-octadecyl phosphate as the dispersant to stabilize the suspension system effectively. In addition, the monomer we employed, PEGMA, also took a role as dispersant, this resulted in the shortage of mono-octadecyl phosphate to reduce the consumption of raw materials effectively. The effects of temperature, the concentration of monomers, the dosage of initiator, crosslinking agent and marcomonomer on the absorbency were studied. At the same time, the kinetics of swelling also was studied. The maximum absorption of the resin reached 930 mL/g and 94 mL/g for deionized water and 0.9 wt % NaCl solution, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A mixture of acrylamide (AM) and acrylic acid (AA) monomers was grafted on gelatinized Amaranthus starch using potassium persulfate (KPS) as an initiator to yield superabsorbent. The effects of different parameters such as time, temperature, monomer feed (AM:AA), starch:monomers ratio and initiator concentration on graft add-on were studied, and the optimized values were found to be 2h, 65°C, 1:1 (w/w), 1:1(w/w) and 1% (with respect to starch powder) respectively. The product so formed was saponified with 0.1N NaOH, dried and finely powdered sample was characterized using FTIR, TGA, and XRD. Product showed maximum absorbency of 155g/g, qualifying itself to be called as superabsorbent. [Copyright &y& Elsevier]

Abstract: A novel superabsorbent composite was synthesized by copolymerization reaction of partially neutralized acrylic acid (AA) on bentonite micropowder using N,N′-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator in aqueous solution. The superabsorbent composite (SAC) was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The water retention test of SAC was also performed. The water absorbency of SAC synthesized was found to be 352 and 110gH2Og−1 in distilled water and 0.2% NaCl, respectively. Sorption capacity of SAC was investigated for heavy metal ions (HMI) using Langmuir and Freundlich model of adsorption. The maximum adsorption capacity (Q m) of HMI onto the bentonite-based SAC from their solution was 1666.67, 270.27, 416.67 and 222.22mgg−1 for Pb(II), Ni(II), Cd(II) and Cu(II), respectively. All results suggested that SAC offers excellent potential for HMI removal from contaminated water. [Copyright &y& Elsevier]