Radiation synthesis of hydrogels to enhance sandy soils water retention and increase plant performance

Preparation and characterization of superabsorbent hydrogels obtained by radiation induced crosslinking of polyacrylamide (PAAm), poly(acrylic acid) (PAAc), poly(vinyl alcohol) (PVA), and potassium polyacrylate (PAAcK) were investigated individually and in (PAAm)–binary systems for possible uses in agricultural fields. The swelling of the investigated hydrogels was mainly related to the type of their hydrophilic functional groups and/or the presence of polarized charges. The preparation conditions, such as irradiation dose and hydrogel blend compositions, that influence the water absorbency of PAAm/PAAcK copolymers and alter their gel content and crosslinking density were investigated. The higher the irradiation dose, the higher the gel content, and the lower the water absorbency. PAAm/PAAcK copolymer, possessing pore structure and fast swelling, was prepared by mixing the hydrogel components with a gas‐forming agent, namely, ammonium carbonate. Studies were also made on the applications of such hydrogels to improve the physical and water retention properties of sandy soil for agricultural purposes. The effect of different types and amounts of hydrogels added to sandy soil on the emergence, vegetative growth, and wilting time of corn (Zea mays) plants was investigated. As the hydrogel level increased, the average of plant height, leaf width, total dry weight, corncob production, and time to wilt increased. The obtained results suggested that the PAAm/PAAcK hydrogels can improve sandy soil properties for cultivation, because they often absorb and keep water one thousand times more than their own weight, reduce watering frequency of the plants, and enhance water retention of soil matrix that results in an increase in plant growth and performance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1360–1371, 2004     

Novel biodegradable superabsorbent hydrogels derived from cotton cellulose and succinic anhydride: Synthesis and characterization

The synthesis of novel superabsorbent hydrogels was investigated with the reaction of cotton cellulose and succinic anhydride (SA) in the presence of 4‐dimethylaminopyridine as an esterification catalyst in a mixture of lithium chloride (LiCl) and N‐methyl‐2‐pyrrolidinone (NMP) or in a mixture of tetrabutylammonium fluoride (TBAF) and dimethyl sulfoxide (DMSO), followed by NaOH neutralization. Interestingly, a hydrogel was obtained without any crosslinking agent, and this indicated the partial formation of a diester between the cellulosic hydroxyl group and SA. The products obtained in LiCl/NMP exhibited superior absorbency to these obtained in TBAF/DMSO. The former absorbed an amount of water about 400 times its dry weight, and this was comparable to a conventional sodium polyacrylate superabsorbent hydrogel. Furthermore, in an aqueous NaCl solution, the absorbency of the product hydrogels was higher than that of the sodium polyacrylate superabsorbent hydrogel. The formed hydrogels biologically degraded almost completely after 25 days, and this showed their excellent biodegradability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3251–3256, 2006     

Hydrogel composites based on linear low‐density polyethylene‐g‐poly (acrylic acid)/Kaolin or halloysite nanotubes

Two series of superabsorbent hydrogel composites were prepared using waste linear low‐density polyethylene, acrylic acid, and two types of clays including kaolin and halloysite nanotube (HNT) through emulsion polymerization. The effects of the clay content on Water absorbency were investigated to obtain a high swelling capacity. The prepared samples were characterized using FTIR, SEM, thermogravimetric analysis, XRD, solid‐state ¹³C Nuclear Magnetic Resonance spectroscopy, and ²⁹Si NMR. SEM characterization of the samples showed that the hydrogel composites have more pores and a higher swelling ratio than the clay‐free hydrogels. The hydrogel composite containing kaolin had higher water absorbency compared to the hydrogel composites with HNT. The swelling behavior of the hydrogel composite was investigated in various saline solutions. The hydrogel composite containing 5 wt % kaolin had the highest water absorbency (760 g/g in distilled water). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40101.     

pH‐sensitive crosslinked guar gum‐based superabsorbent hydrogels: Swelling response in simulated environments and water retention behavior in plant growth media

Crosslinked guar gum‐g‐polyacrylate (cl‐GG‐g‐PA) superabsorbent hydrogels were prepared to explore their potential as soil conditioners and carriers. The hydrogels were prepared by in situ grafting polymerization and crosslinking of acrylamide onto a natural GG followed by hydrolysis. Microwave‐initiated synthesis under the chosen experimental conditions did not exhibit any significant improvement over the conventional technique. The optimization studies of various synthesis parameters, namely, monomer concentration, crosslinker concentration, initiator concentration, quantity of water per unit reaction mass, particle size of backbone, and concentration of alkali were performed. The hydrogels were characterized by wide‐angle X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and solid‐state ¹³C‐NMR spectroscopy. Swelling behavior of a candidate hydrogel [GG‐superabsorbent polymer (SAP)] in response to external stimuli, namely, salt solutions, fertilizer solutions, temperature, and pH, was studied. The GG‐SAP exhibited significant swelling in various environments. The effect of GG‐SAP on water absorption and the retention characteristics of sandy loam soil and soil‐less medium were also studied as a function of temperature and moisture tensions. The addition of GG‐SAP significantly improved the moisture characteristics of plant growth media (both soil and soil‐less), showing that it has tremendous potential for diverse applications in moisture stress agriculture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41060.     

Effect of the anionic‐group/cationic‐group ratio on the swelling behavior and controlled release of agrochemicals of the amphoteric,superabsorbent polymer poly(acrylic acid‐co‐diallyldimethylammonium chloride)

A series of amphoteric, superabsorbent polymers [poly(acrylic acid‐co‐diallyldimethylammonium chloride)] with different molar ratios of anionic groups to cationic groups were prepared by solution polymerization to investigate their swelling behaviors and the controlled release of agrochemicals. Various factors, including the solution pH, the concentrations of different salt solutions, and the temperature, were studied. The dynamic parameters of hydrogels at different temperatures suggested that diffusion was Fickian at lower temperatures, whereas non‐Fickian diffusion prevailed at higher temperatures. A copolymer hydrogel with a low anionic‐group/cationic‐group ratio showed a higher swelling capacity in water and higher salt tolerance. Also, the anionic‐group/cationic‐group ratio was not the dominant factor in determining the water retention. A poly(acrylic acid‐co‐diallyldimethylammonium chloride) hydrogel could control the release of agrochemicals effectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 986–991, 2006     

Carrageenan‐g‐poly(acrylamide)/poly(vinylsulfonic acid,sodium salt) as a novel semi‐IPN hydrogel: Synthesis,characterization, and swelling behavior

A semi‐interpenetrating polymer network (semi‐IPN) hydrogel based on kappa‐carrageenan (κC) and poly (vinylsulfonic acid, sodium salt) (PVSA) was prepared by graft copolymerization of acrylamide (AAm) using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. FTIR spectroscopy was used for confirming the structure of the final product. It was found that the chemical composition of the Semi‐IPN hydrogel is equal to the initial homopolymers and monomer feed compositions. The swelling capacity of the hydrogel was shown to be affected by the MBA, APS, and AAm concentration as well as κC/PVSA weight ratio. The swelling behavior of the hydrogel was also investigated in various pHs and salt solutions. Since the highly swelling biopolymer‐based hydrogel exhibits low salt‐sensitivity, it may be referred to as an anti‐salt superabsorbent hydrogel. The swelling kinetics of the superabsorbent hydrogels was studied as well. POLYM. ENG. SCI., 47:1388–1395, 2007. © 2007 Society of Plastics Engineers     

Effect of hydrophobic monomer on the synthesis and swelling behaviour of a collagen‐graft‐poly[(acrylic acid)‐co‐(sodium acrylate)] hydrogel

BACKGROUND: Graft polymerization of vinylic monomers onto natural backbones is an efficient approach for the synthesis of natural‐based superabsorbents. The nature of the monomers will affect the swelling behaviour of the superabsorbents. Here, a novel superabsorbent was synthesized through grafting of acrylic acid onto collagen in the presence of hydrophobic styrene as co‐monomer. Subsequently, the effect of styrene on the swelling behaviour of the superabsorbent was studied. RESULTS: The highly swelling superabsorbent was prepared by introducing styrene into a collagen‐graft‐poly(acrylic acid) hydrogel. By inclusion of styrene monomer, the swelling capacity of the hydrogel was increased; this is discussed according to the network composition. The effect of swelling media (salt solutions and various pH values) was investigated. The results of absorbency under load showed that hydrogels containing phenyl groups exhibit better behaviour; however, by introducing styrene, the rate of water uptake and resistance to water holding under heating was reduced. Scanning electron micrographs of hydrogels revealed a decrease in porosity on using styrene. CONCLUSION: Inclusion of styrene monomer in the ionic superabsorbent caused high swelling capacity with better absorbency under load. This can be used to prepare highly swelling superabsorbents with good mechanical properties. The pH reversibility of the synthesized superabsorbent makes it a candidate for use in the controlled release of drugs and in agrochemicals. Copyright © 2008 Society of Chemical Industry     

Optimization of synthesis conditions of a novel carrageenan‐based superabsorbent hydrogel by Taguchi method and investigation of its metal ions adsorption

The Taguchi method, a robust experimental design, was used for optimization of synthesis of a novel biopolymer‐based superabsorbent hydrogel, kappa‐carrageenan (κ‐C)‐g‐acrylic acid (AA)‐co‐2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS). The Taguchi method was applied for the experimental and standard 18 orthogonal arrays (OA) with seven factors and three levels for each factor. In the synthesis of the superabsorbent, N,N'‐methylene bisacrylamide (MBA) as crosslinker, ammonium persulfate (APS) as initiator, monomer ratio (AA/AMPS), κ‐C concentration, Total Monomer, neutralization percent (NU), and reaction temperature were used as important factors. After analyzing with analysis of variance (ANOVA) results showed that maximum water absorption capability for optimized final product was found to be 1195 g water per one gram of dry hydrogel powder. The proposed mechanism for the grafting and chemically crosslinking reactions was proved with FTIR, SEM, and TGA methods. Furthermore, the absorption capability of the hydrogels towards bivalent metal ions was evaluated. Therefore, the hydrogels may be based‐considered as a candidate to develop an efficient biofilm absorbent in water treatment applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel superabsorbent materials from bacterial cellulose

A novel process for the production of superabsorbent materials (hydrogels) from bacterial cellulose (BC) was developed. Prior to crosslinking with a water‐soluble polyethylene glycol diacrylate (PEGDA), BC was first carboxymethylated and functionalized with glycidyl methacrylate. The degree of crosslinking influenced the swelling properties of the hydrogels. The use of greater amounts of PEGDA enhanced the formation of a thicker macromolecular network containing fewer capillary spaces in the crosslinked gel. The maximum water retention value of the hydrogels containing 2.5–3.5 mmol of carboxyl groups per gram of gel reached 125 g g^?1 in distilled water, and 29 g g^?1 in saline (0.9% NaCl solution). The highly porous hydrogel architecture with a pore size of 350–600 µm created a high specific surface area. This enables rapid mass penetration in superabsorbent applications. The superabsorbent hydrogels reached 80% of their maximum water absorption capacity in 30 min. © 2018 Society of Chemical Industry     

Preparation,water absorbency,and enzyme degradability of novel chitin‐ and cellulose/chitin‐based superabsorbent hydrogels

Superabsorbent hydrogels were prepared from chitin dissolved in lithium chloride and N‐methyl‐2‐pyrrolidinone by esterification crosslinking with 1,2,3,4‐butanetetracarboxylic dianhydride (BTCA). The absorbency of the chitin hydrogel was strongly dependent on the ratio of BTCA feed to chitin. The hydrogel prepared at the feed ratio of 5 showed the highest absorbency (345 g/g‐polymer), and the hydrogel was composed of 0.65 molecules of BTCA per monomer unit of chitin. The hydrogels exhibited good biodegradability by chitinase with a maximum degradation of 91% within 7 days. This method for obtaining the chitin hydrogel was also applicable to cellulose and chitin mixtures, and 1 : 1 cellulose/chitin hybrid hydrogels could be obtained by the esterification crosslinking of a mixture with a 1 : 1 molar ratio of cellulose and chitin. The optimal BTCA feed ratio of 5 resulted in the cellulose/chitin hydrogel with the highest water absorbency (329 g/g‐polymer), and the hydrogel contained 0.65 molecules of BTCA per polysaccharide monomer unit. In addition, the hybrid hydrogels were degraded by cellulase as well as chitinase. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Partially hydrolyzed kappa carrageenan—polyacrylonitrile as a novel biopolymer‐based superabsorbent hydrogel: Synthesis,characterization, and swelling behaviors

In this paper, synthesis and swelling behavior of a novel superabsorbent hydrogel based on kappa carrageenan (κC) and polyacrylonitrile (PAN) was investigated. To achieve partially hydrolyzed κC‐PAN hydrogel, physical mixture of κC and PAN was hydrolyzed by NaOH solution. During alkaline hydrolysis, the nitrile groups of PAN are converted to a mixture of hydrophilic carboxamide and carboxylate groups follow by in situ crosslinking of the grafted PAN chains. The reaction variables affecting on the swelling capacity of the hydrogel were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. Under the optimized conditions concluded, super swelling hydrogel with the ability of water absorption up to 3260 g/g (water/dry hydrogel powder) has been prepared. Swelling measurements of the synthesized hydrogels was carried out in various salt solutions and solutions with different pH. The results indicate that the hydrogels have good pH sensitivity and pH‐reversible property between pH 2 and pH 8. POLYM. ENG. SCI. 46:1778–1786, 2006. © 2006 Society of Plastics Engineers.     

Hydrogels composite of poly(acrylamide‐co‐acrylate) and rice husk ash. I. Synthesis and characterization

Composite hydrogels of poly(acrylamide‐co‐acrylate) with rice husk ash (RHA) were synthesized and studies of the swelling variables were accomplished comparatively with commercial polyacrylamide gel and PAMACRYL, a poly(acrylamide‐co‐acrylate) hydrogel without RHA. FT‐IR and WAXS were the techniques employed for characterizing a series of hydrogel obtained by varying the percentage of RHA (1, 2, 5, 10, and 20 wt %) and the amount of crosslinking agent (0.05, 0.1, and 0.2 mol %) relative to sum of AAm and AAc. Superabsorbent hydrogel with W_eq > 800 g H₂O/g gel was obtained with percentage of 10 wt % of RHA and 0.1 of crosslinking agent mol %. The hydrogel showed to be sensitive to the pH variation and to the presence of salts. The hydrogels, even though submitted through cycles of drying and swelling, preserved their superabsorbent characteristics and demonstrated better water absorbance properties when compared with commercial polyacrylamide gel. The composite hydrogels of poly(acrylamide‐co‐acrylate) with RHA presented good characteristics to be applied as soil conditioner for using in agriculture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

New smart carrageenan‐based superabsorbent hydrogel hybrid: Investigation of swelling rate and environmental responsiveness

Synthesis of novel natural‐based superabsorbents with improved properties is of prime importance in many applications. In this article we report an efficient synthesis of new polysaccharide‐based superabsorbent hybrid composing carrageenan, acrylic acid, sodium acrylate, and 2‐hydroxyethyl acrylate through homogenous solution polymerization process. Infrared spectroscopy and thermogravimetric analysis (TGA) were carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was examined by scanning electron microscopy (SEM). To deeper studies on the structure‐property relation in SAP hydrogels, three hydrogels with different acrylic acid/2‐hydroxyethyl acrylate (AA/HEA) weight ratios were synthesized and swelling capacity in various media was assessed. The hydrogel hybrid was also tested to be swollen and deswollen alternatively in 0.01 and 0.1 M sodium chloride solution. Moreover, the swelling‐deswelling capability of the hydrogel in alternatively changed methanol‐water mixtures was studied. Additionally, the swelling kinetics of the synthesized hydrogels were examined. The absorbency under load (AUL) of hydrogel was also investigated by using an AUL tester at various applied pressures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Nanoarchitectonics for Biodegradable Superabsorbent Based on Carboxymethyl Starch and Chitosan Cross-Linked with Vanillin

Due to the growing demand for sustainable hygiene products (that will exhibit biodegradability and compostability properties), the challenge of developing a superabsorbent polymer that absorbs significant amounts of liquid has been raised so that it can be used in the hygiene sector in the future. The work covers the study of the swelling and dehydration kinetics of hydrogels formed by grafting polymerization of carboxymethyl starch (CMS) and chitosan (Ch). Vanillin (Van) was used as the crosslinking agent. The swelling and dehydration kinetics of the polymers were measured in various solutes including deionized water buffers with pH from 1 to 12 and in aqueous solutions of sodium chloride at 298 and 311 K. The surface morphology and texture properties of the analyzed hydrogels were observed by scanning electron microscopy (SEM). The influence of this structure on swelling and dehydration is discussed. Fourier transform infrared (FTIR) analyses confirmed the interaction between the carboxymethyl starch carbonyl groups and the chitosan amino groups in the resulting hydrogels. Additionally, spectroscopic analyses confirmed the formation of acetal crosslink bridges including vanillin molecules. The chemical dynamics studies revealed that new hydrogel dehydration kinetics strongly depend on the vanillin content. The main significance of the study concerns the positive results of the survey for the new superabsorbent polymer material, coupling high fluid absorbance with biodegradability. The studies on biodegradability indicated that resulting materials show good environmental degradability characteristics and can be considered true biodegradable superabsorbent polymers.     

Synthesis of crosslinked superabsorbent carboxymethyl cellulose/acrylamide hydrogels through electron‐beam irradiation

A study on the possibility of the preparation of superabsorbent hydrogels based on crosslinked carboxymethyl cellulose polymer and acrylamide monomer through electron‐beam irradiation was carried out. The effects of the irradiation dose and polymer–monomer compositions on the crosslinking density were studied. The hydrophilic properties of the superabsorbent hydrogels were identified by the swelling percentage. The prepared hydrogels had higher swelling in distilled water than in salt solutions. Moreover, the hydrogels exhibited the highest swelling at pH 7. Also, increasing the temperature up to 50°C caused an increase in the swelling. The thermal properties of the hydrogels were characterized with thermogravimetric analysis. The use of the prepared superabsorbent hydrogels for the growth of rice was also investigated through the water‐retention property. The water retention in the soil was enhanced with the hydrogels. Superabsorbent hydrogels based on carboxymethyl cellulose polymer and acrylamide monomer could be considered as water‐managing materials for agriculture and horticulture in desert and drought‐prone areas. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2003–2008, 2007     

Mechanical Strengths of Hydrogels of Poly(N,N‐Dimethylacrylamide)/Alginate with IPN and of Poly(N,N‐Dimethylacrylamide)/Chitosan with Semi‐IPN Microstructures

Tough hydrogels receive continuous attention because of their promising applications in many fields. Herein, tough hydrogels of poly (N,N‐dimethylacrylamide) (PDMAA)/alginate (SA) are prepared, with interpenetrating network (IPN) and of PDMAA/chitosan (CS) with semi‐IPN microstructure, respectively. The toughening of the hydrogel by incorporating natural polymers is studied by compressing tests and dynamic mechanical analyses. Moreover, cyclic load–unload compressing of the two types of hydrogels are performed at low strains and under relatively high strains, in order to compare their strength and anti‐fatigue properties. The results indicate that the mechanical strength can be markedly improved upon addition of the natural polymers, and the IPN hydrogel of PDMAA/SA reveals much higher mechanical performances but is less stable. However, the semi‐IPN hydrogel of PDMAA/CS displays excellent anti‐fatigue stability, but with relatively low strength. Swelling tests, scanning electron microscopy, and Fourier transform infrared spectroscopy are carried out to study the microstructures of the hydrogels, which are carefully analyzed to understand the difference in mechanical performances of those hydrogels. The results suggest that the presence of sacrificial unit and higher chain density in the IPN are helpful for toughening hydrogels, while the semi‐IPN network is beneficial to improve the energy dissipation efficiency.     

Synthesis and superswelling behavior of carboxymethylcellulose–poly(sodium acrylate‐co‐acrylamide) hydrogel

In this paper, attention is paid to synthesis and swelling behavior of a superabsorbent hydrogel based carboxymethylcellulose (CMC) and polyacrylonitrile (PAN). The physical mixture of CMC and PAN was hydrolyzed in NaOH solution to yield hydrogel, CMC–poly(NaAA‐co‐AAm). During alkaline hydrolysis, the nitrile groups of PAN were completely converted to a mixture of hydrophilic carboxamide and carboxylate groups followed by in situ crosslinking of the grafted PAN chains. A proposed mechanism for hydrogel formation was suggested and the structure of the product was established using FTIR spectroscopy. The reaction variables affecting the swelling capacity of the hydrogel were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. Swelling measurements of the synthesized hydrogels in various chloride salt solutions indicated a swelling‐loss with increase in the ionic strength of the salt solutions. The pH of the various solutions also affected the swelling of the superabsorbent. Furthermore, the present hydrogels showed a pH‐reversible property. Finally, the swelling kinetics of synthesized hydrogels with various absorbent particle sizes was briefly examined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biodegradable superabsorbent hydrogel for water holding in soil and controlled-release fertilizer

The bio-based environment-friendly functional polymers are the most desired materials for the society. Thus, a superabsorbent hydrogel (SAH) of starch-modified poly(acrylic acid) was reported and the concentrations of reactants, initiators, and crosslinkers were optimized to achieve the highest water absorption (>700 g/g). The chemical structure of SAH was supported by solid-state ¹³C nuclear magnetic resonance and Fourier-transform infrared spectroscopic studies. The hydrogels were found to be biodegradable and possess high water absorption capacity. After the addition of 0.25% of the hydrogel, water-holding capacity of the soil was enhanced by 120%. Significant effect was also observed on bulk density and porosity of the soil after the addition of SAH. Furthermore, urea-encapsulated SAH can be used as a controlled release fertilizer for crops, as indicated by a preliminary study on the growth rate of chick pea (Cicer arietinum) plant. Thus, SAH has the potential to be used as a controlled-release carrier and water-conserving agent in different fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48495.     

Radiation synthesis of kappa-carrageenan/acrylamide graft copolymers as superabsorbents and their possible applications

Kappa-carrageenan (κC) was modified via graft copolymerization of acrylamide (AAm) using γ-irradiation and followed by alkaline hydrolysis to achieve a novel superabsorbent hydrogel. The effect of grafting variables and alkaline hydrolysis conditions such as κC/AAm compositions and irradiation doses, NaOH concentration, hydrolysis time and temperature were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. Swelling properties and FT-IR of untreated κC-g-PAAm and hydrolyzed κC-g-PAAm (H-κC-g-PAAm) were determined. The swelling capacity of hydrolyzed κC-g-PAAm was about 10 times in distilled water and three times in NaCl solution higher than that for κC-g-PAAm. The swelling of superabsorbing hydrogels was examined in buffer solutions. The swelling capacity of hydrogels was also measured in various salt solutions (LiCl, NaCl, KCl, CaCl₂, and FeCl₃). Results indicated that the swelling ratios decreased with an increase in the ion radius, valence and ionic strength of the salt solutions. Due to their high swelling ability in salt solutions, the hydrogels may be referred to as ‘anti-salt superabsorbent’ polymers. Thus, the salinity of water treated with H-κC-g-PAAm hydrogels was determined. It was found that the H-κC-g-PAAm hydrogels have a capability to absorb and retain the fresh water from the saline solution. The results obtained suggested the possible used of such prepared superabsorbent in agricultural purposes as a material for sodic soil remediation.     

Swelling properties of CMC‐g‐poly (AAm‐co‐AMPS) superabsorbent hydrogel

A series of biopolymer‐based superabsorbent hydrogels based on carboxymethyl cellulose has been prepared by free‐radical graft copolymerization of acrylamide and 2‐acrylamido‐2‐methylpropan sulfonic acid (AMPS) in aqueous solution using methylenebisacrylamide as a crosslinking agent and ammonium persulfate as an initiator. The effect of variables on the swelling capacity such as: acrylamide/AMPS weight ratio, reaction temperature, and concentration of the initiator and crosslinker were systematically optimized. The results indicated that with increasing the amount of AMPS, the swelling capacity is increased. FT‐IR spectroscopy and scanning electron microscope analysis were used to confirm the hydrogel structure. Swelling measurements of the synthesized hydrogels in different salt solutions indicated considerable swelling capacity. The absorbency under load of the superabsorbent hydrogels was determined by using an absorbency under load tester at various applied pressures. A preliminary swelling and deswelling behaviors of the hydrogels were also studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009