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     

Study on superabsorbent composite. XX. Effects of cation‐exchanged montmorillonite on swelling properties of superabsorbent composite containing sodium humate

In this work, the effects of different cation‐exchanged montmorillonite on water absorbency of poly(acrylic acid‐co‐acrylamide)/montmorillonite/sodium humate (PAA‐AM/MMT/SH) superabsorbent composite were systematically investigated under the same preparation conditions. The superabsorbents doped with different cation‐exchanged montmorillonite were characterized by Fourier‐transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy technologies. Swelling behaviors of developing superabsorbent composite in various cationic saline solutions (NaCl, CaCl₂, and FeCl₃) were also investigated. The water absorbencies of superabsorbent composite with 20 wt% MMT and 30 wt% SH are 638, 723, 682, and 363 g g⁻¹ in distilled water for incorporating natural Na⁺‐MMT, Li⁺‐exchanged MMT, Ca²⁺‐exchanged MMT, and Al³⁺‐exchanged MMT, respectively. The results showed that the cation‐exchange process had some obvious influences on final water absorbency of superabsorbent composite. NaCl, CaCl₂, and FeCl₃ solutions did not alter the swelling characteristics of the superabsorbent materials at a concentration of less than 0.01 mM, however, a concentration of greater than 0.1 mM caused a collapse in the swelling curves. The excellent swelling‐reswelling‐swelling behavior and lower swelling rate testified that Al³⁺‐exchanged MMT can act as an assistant crosslinker in the polymeric network. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Synthesis and properties of poly(sodium acrylate‐co‐2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid)/attapulgite as a salt‐resistant superabsorbent composite

A novel salt‐resistant superabsorbent composite was prepared by copolymerization of partially neutralized acrylic acid, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid (AMPS) and attapulgite (APT). To enhance the swelling rate (SR) of the copolymer, sodium bicarbonate was used as a foaming agent in the course of copolymerization. Furthermore, for improving the properties of swollen hydrogel, such as strength, resilience and dispersion, the copolymer was surface‐crosslinked with glycerine and sodium silicate, and then the surface‐crosslinked copolymer was blended with aluminum sulfate and sodium carbonate in post treatment process. The influences of some reaction conditions, such as amount of AMPS, APT, and initiator, and neutralization degree of acrylic acid on water absorbency in 0.9 wt% NaCl aqueous solution both under atmospheric pressure (WA) and load (WA_P, P ≈ 2 × 10³ Pa) were investigated. In addition, the effect of them on SR was also studied. The WA and WA_P of the superabsorbent composite prepared under optimal conditions in 0.9 wt% NaCl aqueous solution were 52 g·g^?1 and 8 g·g^?1, respectively. Besides, the SR was fast, and it could reach 0.393 mL·(g·s)^?1. Moreover, the swollen hydrogel possessed excellent salt resistance, hydrogel resilience and dispersion. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Superabsorbent composite. XIII. Effects of Al3+‐attapulgite on hydrogel strength and swelling behaviors of poly(acrylic acid)/Al3+‐attapulgite superabsorbent composites

Al³⁺‐attapulgite (Al³⁺‐APT) was prepared by treating attapulgite (APT) with AlCl₃ aqueous solution of various concentrations. The poly(acrylic acid)/Al³⁺‐attapulgite (PAA/Al³⁺‐APT) superabsorbent composite was prepared by reaction of partly neutralized acrylic acid, and Al³⁺‐APT in aqueous solution using N, N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The surface morphology of the composite was investigated by SEM, and the Al³⁺‐APT composite generated a relatively planar surface comparing the nature APT. The effects of Al³⁺‐APT on hydrogel strength and swelling behaviors, such as equilibrium water absorbency, swelling rate, and reswelling capability, of the superabsorbent composites were also studied. The hydrogel strength and reswelling capability were improved, however, the equilibrium water absorbency and swelling rate decreased with increasing AlCl₃ solution concentration. The equilibrium water absorbency firstly increased, and then decreased with increasing Al³⁺‐APT content. The results indicate that Al³⁺‐APT acts as an assistant crosslinker in the polymeric network, which has great influences on hydrogel strength and swelling behaviors of the PAA/Al³⁺‐APT superabsorbent composites. POLYM. ENG. SCI., 47:619–624, 2007. © 2007 Society of Plastics Engineers.     

Fast‐swelling superabsorbent polymers with polymerizable macromolecular surfactant as crosslinker

Fast‐swelling superabsorbent polymers (SAPs) have been prepared by micellar cross‐linking copolymerization of acrylic acid and acrylamide using polymerizable macromolecular surfactants (PMSs) as multifunctional crosslinkers, with a foaming technique. Sodium bicarbonate (NaHCO₃)/acetone and Pluronic F127 were used as foam (or porosity) generators and stabilizer, respectively. It has been found that the PMSs with different polyethylene glycol (PEG) chain length have little effect on the swelling rate of the SAPs, while the foam generators are crucial. In addition, the monomer concentration and the concentration of the PMS are important to the fast swelling rate of the SAPs. For a balance of a relatively fast‐swelling rate, high water absorbency under load and low cost in drying, a monomer concentration of above 50%, 0.08% PMS, and 5% NaHCO₃ are preferable. The water absorbency of SAP prepared under optimal conditions could reach half of equilibrium water absorbency in 30 seconds and the saline water absorbency under load could reach 18.4 g/g. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44173.     

Study on superabsorbent composite XXV. Synthesis,characterization, and swelling behaviors of poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composites

In this work, a novel poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composite was prepared by graft copolymerization among acrylic acid, N‐acryloylmorpholine and attapulgite in aqueous solution, using N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The result from FTIR spectra showed that  OH of attapulgite participated in graft copolymerization with acrylic acid and N‐acryloylmorpholine. Proper monomer ratio and atapulgite content could form a loose surface, and improve reswelling ability and initial swelling rate. The buffer action of the  COOH and  COO⁻ groups in the superabsorbent composite keeps the water absorbency a rough constant in the pH range of 4.4–9.6. Both polarity and structure of an organic solvent are responsible for the phase transition point of the superabsorbent composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Swelling study of superabsorbent PAA‐co‐PAM/clay nanohydrogel

A series of superabsorbent composites were prepared from acrylic acid (AA), acrylamide (AM), and Cloisite® 30B by aqueous solution polymerization technique using ammonium peroxodisulfate (APS) as initiator. The interaction of the organically modified nanoclay with PAA‐co‐PAM copolymer was verified by FTIR, whereas the morphology of the composite was studied by Scanning Electron Microscopy (SEM). The water absorbency in deionized water and saline water of the synthesized nanohydrogels was measured by calculating their percentage swelling ratio. The effects of copolymerization, monomer ratio, clay content, and temperature on the water absorbency were studied. The results indicated a considerable increase in swelling ratio by proper monomer proportion and incorporation of optimum clay percentage into the copolymer matrix. It was found that the nanohydrogel acquired highest water absorbency with 2% clay loading. The reswelling ability and water retention capacity of the PAA‐co‐PAM hydrogel and PAA‐co‐PAM/clay nanohydrogel were also measured. The water absorbency was found to increase after each reswelling for which it may be useful as recyclable superabsorbent material. The results of water retention capacity of the nanohydrogel were also encouraging and find application in agriculture, especially in drought‐prone areas. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis,characterization and swelling behaviors of hydroxyethyl cellulose‐g‐poly(acrylic acid)/attapulgite superabsorbent composite

In this work, a series of novel hydroxyethyl cellulose‐ g‐poly(acrylic acid)/attapulgite (HEC‐g‐PAA/APT) superabsorbent composites were prepared through the graft polymerization of hydroxyethyl cellulose (HEC), partially neutralized acrylic acid (AA), and attapulgite (APT) in aqueous solution, and the composites were characterized by means of Fourier‐transform spectroscopy, scanning electron microscopy, and transmission electronmicroscopy. The effects of polymerization variables including concentrations of the initiator and crosslinker and APT content on water absorbency were studied, and the swelling properties in various pH solutions as well as the swelling kinetics in various saline solutions were also systematically evaluated. Results showed that the introduction of 5 wt% APT into HEC‐g‐PAA polymeric network could improve both water absorbency and water absorption rate of the superabsorbent composites. In addition, the superabsorbent composites retained high water absorbency over a wide pH range of 4–10, and the swelling kinetics of the superabsorbent composites in CaCl₂ and FeCl₃ solutions exhibited a remarkable overshooting phenomenon. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Superabsorbent composite XXII: Effects of modified sepiolite on water absorbency and swelling behavior of chitosan‐g‐poly(acrylic acid)/sepiolite superabsorbent composite

In this work, a series of chitosan‐g‐poly(acrylic acid)/sepiolite (CTS‐g‐PAA/ST) superabsorbent composites containing raw sepiolite, acid‐activated sepiolite, and cation‐exchanged sepiolite were synthesized by free‐radical graft polymerization in aqueous solution, using N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The effects of raw sepiolite, acid‐activated sepiolite, and cation‐exchanged sepoilite on equilibrium water absorbency, swelling rate, and swelling behavior in different pH value solution of superabsorbent composites were systematically investigated. The results from FTIR spectra showed that chitosan and sepiolite participated in graft polymerization reaction with acrylic acid. The introduction of acid‐activated and cation‐exchanged sepiolite into chitosan‐g‐poly(acrylic acid) polymeric network could improve water absorbency and swelling rate compared with that of the raw sepiolite. All prepared samples have similar swelling behavior in different pH solutions and the equilibrium water absorbencies of samples keep roughly constant in the pH range from 4 to 12. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Synthesis,swelling behaviors,and slow‐release characteristics of a guar gum‐g‐poly(sodium acrylate)/sodium humate superabsorbent

Superabsorbents used in agricultural and ecological projects with low‐cost, slow‐release fertilizers and environmentally friendly characteristics have been extensively studied. The use of a natural polymer as the matrix and then further polymerization with some functional material has become the preferred method. In this work, with natural guar gum (GG), partially neutralized acrylic acid, and sodium humate (SH) as the raw materials, ammonium persulfate as the initiator, and N,N′‐methylenebisacrylamide (MBA) as the crosslinker, GG‐g‐poly(sodium acrylate) (PNaA)/SH superabsorbents were synthesized through a solution polymerization reaction and were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The effects of the SH content and MBA concentration on the water absorbency were investigated. The results showed that the introduction of SH into the GG‐g‐PNaA system could improve the water absorbency, swelling rate, pH‐resistant property, and reswelling capability, and the superabsorbent containing 15 wt % SH had the highest water absorbency of 532 g/g of sample in distilled water and 62 g/g of sample in a 0.9 wt % NaCl solution. The slow release in water and water retention in sandy soil tests revealed that the superabsorbent could act as a fertilizer as well as an effective water‐saving material for agricultural applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of poly(sodium acrylate‐co‐sodium 1‐(acryloyloxy) propan‐2‐yl phosphate) and comparative study on its swelling properties with poly(sodium acrylate) and poly(sodium acrylate‐co‐2‐hydroxypropyl acrylate)

A new superabsorbent copolymer, poly(sodium acrylate‐co‐sodium 1‐(acryloyloxy) propan‐2‐yl phosphate) [P(SA‐co‐SAPP)], was synthesized by a novel prepared monomer, 1‐(acryloyloxy) propan‐2‐yl phosphoryl dichloride. The swelling properties of the superabsorbent were investigated by comparison with poly(sodium acrylate) (PSA) and the copolymer of poly(sodium acrylate‐co‐2‐hydroxypropyl acrylate) [P(SA‐co‐HPA)]. The results showed that (1) the superabsorbent containing sodium 1‐(acryloyloxy) propan‐2‐yl phosphate had higher water absorbency at general testing conditions; (2) the swelling properties of P(SA‐co‐SAPP) and PSA were obviously influenced by pH of solutions, which were different from that of P(SA‐co‐HPA); (3) the swelling process and the saturated water absorbency of all superabsorbents were remarkably affected by cations, especially multivalent ones, while barely affected by anions. POLYM. ENG. SCI., 47:728–737, 2007. © 2007 Society of Plastics Engineers.     

Fast‐swelling oxidized starch phosphate–poly(acrylate/acrylamide/2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid) superabsorbent composite

A fast‐swelling superabsorbent composite was prepared by solution polymerization of acrylate, acrylamide, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid and oxidized starch phosphate. Ethanol, propyl alcohol, butyl alcohol, and sodium bicarbonate were used as foaming agents to produce fast‐swelling characteristics. The structure of the superabsorbent composite was characterized using Fourier transform infrared spectroscopy (FTIR). The influences of the amount of water, acrylamide, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid, oxidized starch phosphate, initiator, and trihydroxymethyl propane glycidol ether, as well as the neutralization degree of acrylic acid on the equilibrium swelling degree and swelling rate of the superabsorbent composite, were investigated. The equilibrium swelling degree of the superabsorbent composite prepared in a 0.9 wt% NaCl aqueous solution was 52 g g^?1, and the swelling rate reached 0.86 mL g^?1 s^?1. The swelling kinetics was also investigated, and the results indicate that swelling of the superabsorbent composites obeys Schott's pseudo second‐order kinetics model. POLYM. ENG. SCI., 56:1267–1274, 2016. © 2016 Society of Plastics Engineers     

Preparation and swelling properties of semi‐IPN hydrogels based on chitosan‐g‐poly(acrylic acid) and phosphorylated polyvinyl alcohol

The phosphorylated poly(vinyl alcohol) (P‐PVA) samples with various substitution degrees were prepared through the esterification reaction of PVA and phosphoric acid. By using chitosan (CTS), acrylic acid (AA) and P‐PVA as raw materials, ammonium persulphate (APS) as an initiator and N,N‐methylenebisacrylamide as a crosslinker, the CTS‐g‐PAA/P‐PVA semi‐interpenetrated polymer network (IPN) ssuperabsorbent hydrogel was prepared in aqueous solution by the graft copolymerization of CTS and AA and followed by an interpenetrating and crosslinking of P‐PVA chains. The hydrogel was characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) techniques, and the influence of reaction variables, such as the substitution degree and content of P‐PVA on water absorbency were also investigated. FTIR and DSC results confirmed that PAA had been grafted onto CTS backbone and revealed the existence of phase separation and the formation of semi‐IPN network structure. SEM observations indicate that the incorporation of P‐PVA induced highly porous structure, and P‐PVA was uniformly dispersed in the polymeric network. Swelling results showed that CTS‐g‐PAA/P‐PVA semi‐IPN superabsorbent hydrogel exhibited improved swelling capability (421 g·g^?1 in distilled water and 55 g·g^?1 in 0.9 wt % NaCl solution) and swelling rate compared with CTS‐g‐PAA/PVA hydrogel (301 g·g^?1 in distilled water and 47 g·g^?1 in 0.9 wt % NaCl solution) due to the phosphorylation of PVA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of a salt‐resistant superabsorbent polymer

Crosslinked sodium polyacrylate was prepared by solution polymerization with N,N‐methylene‐bisacrylamide (bisAM) as crosslinking agent; it was subsequently surface‐crosslinked by ethylene glycol diglycidyl ether (EGDE) and then was modified with inorganic salt to obtain a superabsorbent with water absorbency in 0.9 wt % NaCl aqueous solution at atmosphere and applied pressure (P ≈ 2 × 10³ Pa) of 55 and 20 g.g^?1, respectively. Moreover, it also had excellent hydrogel strength. The effects of reaction temperature, reaction time, neutralization degree (ND) of acrylic acid, amount of initiator, crosslinking agent, and surface‐crosslinking agent, mass ratio of inorganic salt to initial superabsorbent, molar ratio of sodium aluminate (NaAlO₂) to potassium dihydrogen hyphosphate (KH₂PO₄) on water absorbency (WA) in 0.9 wt % NaCl aqueous, and the hydrogel modulus were investigated and optimized. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2532–2541, 2004     

Preparation and properties of porous poly(sodium acrylate‐co‐acrylamide) salt‐resistant superabsorbent composite

A novel semi‐interpenetrating polymer networks (semi‐IPNs) porous salt‐resistant superabsorbent composite was prepared by copolymerization of partially neutralized acrylic acid and acrylamide using polyethylene glycol as semi‐IPNs composite, N,N′‐methylenebisacrylamide, triene propanol phosphate, and trihydroxymethyl propane glycidol ether as crosslinking agents, methanol, propanol, and butanol as foaming agents, and L ‐ascorbic acid and peroxide hydrogen as initiators. To improve the properties of swollen hydrogel, such as strength, resilience, permeabilities, and dispersion, the copolymer was surface‐crosslinked, and then blended with aluminum sulfate, sodium carbonate, and sodium 1‐octadecanol phosphate in the course of post treatment. The influences of reaction conditions on properties of superabsorbent composite were investigated and optimized, and the water absorbency of superabsorbent composite prepared at optimal conditions in 0.9 wt% NaCl aqueous solution under atmospheric pressure and certain load (P ≈ 2 × 10³ Pa) were 61 g g^?1 and 16.7 g g^?1, respectively. Moreover, the swelling rate reached 22.003 × 10^?3 g (g s)^?1. And the excellent hydrogel properties, such as hydrogel strength, resilience, permeabilities, and dispersion were also obtained. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Synthesis of AA‐based superabsorbent interpenetrated with sodium PVA sulfate

An interpenetrating network of acrylic acid (AA)‐based superabsorbents and sodium PVA sulfate (SPS) were prepared by copolymerizing AA and N,N′‐methylene bisacrylamide as a crosslinking monomer in a solution of SPS with KPS, a radical initiator. The SPS was prepared through the sulfation of the hydroxyl groups of PVA with DMF‐SO₃ complex in DMSO. The AA‐based superabsorbent interpenetrated with SPS (SA‐IP‐SPS) showed superior properties such as higher water and saline absorbency, absorbency under load (AUL), and water retention value (WRV) compared with AA‐based superabsorbent due to the interpenetrated SPS. The maximum water and saline absorbency of SA‐IP‐SPS was 1753 and 125.6 g/g, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2525–2532, 2000     

Study on superabsorbent composite. XV. Effects of ion‐exchanged attapulgite on water absorbency of superabsorbent composites

A series of superabsorbent composite, polyacrylamide/attapulgite, from acrylamide (AM) and ion‐exchanged attapulgite (APT) was prepared by aqueous polymerization, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The effects of ion‐exchanged APT on water absorbency of superabsorbent composites in distilled water and in 0.9 wt% NaCl solution were studied. The result indicates that higher cation‐exchange capacity (CEC) and lower specific surface area (SSA) of APT treated with various anions are of benefit for improving water absorbency in distilled water. The effects of AlCl₃ solution concentration and Al³⁺‐exchanged APT content on water absorbency of the composite were also investigated. The concentration of AlCl₃ solution has a great influence on water absorbency of the superabsorbent composite. Al³⁺‐exchange of APT could also enhance reswelling ability of the corresponding composite, which indicates that Al³⁺‐exchange of APT could improve gel strength and gives a direct evidence for its acting as an inorganic assistant crosslinker in the polymeric network. POLYM. COMPOS., 28:208–213, 2007. © 2007 Society of Plastics Engineers     

Preparation and water absorbency of a novel poly(acrylate‐co‐acrylamide)/vermiculite superabsorbent composite

A novel poly(acrylate‐co‐acrylamide)/expanded vermiculite (EVMT) superabsorbent composite was synthesized by aqueous solution polymerization method. The water absorbency of the superabsorbent composite still reaches 850 g/g when 50 wt % EVMT is added, which is significant in decreasing the production cost of the superabsorbent composites. By controlling the molar ratio of acrylic acid monomer and acrylamide monomer, and neutralization degree of acrylic acid, the hydrophilic groups on the composite can be adjusted, and it is found that the collaborative absorbent effect of ? CONH₂, ? COOK, and ? COOH groups is superior to that of single ? CONH₂, ? COOK, or ? COOH group. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 735–739, 2007     

Synthesis and swelling behaviour of poly (sodium acrylate)/sepiolite superabsorbent composites and nanocomposites

A series of novel composites and nanocomposites xerogels based on acrylic acid, sepiolite and N,N′‐methylenebisacrylamide were prepared using a solution polymerization technique at 70 °C. The quality of dispersion of the micronized sepiolite in the monomer is the crucial point for obtaining nanocomposites. A good dispersion explains the improvement of the absorbent properties of the nanocomposites with respect to the composites. This work investigates not only the influence of the mixing procedure on the swelling behaviour, but also the effect of the amount of clay on the absorbency of these hydrogels in deionized water and saline solution (0.2 wt% NaCl_(aq)). A crosslinker concentration of 5 wt% sepiolite nanocomposite superabsorbent was shown to give the best results (1419 g g^?1). Moreover, experimental results indicate that the absorbency in saline solution is smaller than that in deionized water. Rates of swelling for these absorbents were found to fit the Voigt expression. Finally, the model approximates Case II sorption in the early stages of the swelling process and Case I in the later stages. Copyright © 2006 Society of Chemical Industry     

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