Swelling behavior of novel protein‐based superabsorbent nanocomposite

A novel superabsorbent nanocomposite based on hydrolyzed collagen was synthesized by simultaneously graft copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and acrylamide (AAm). Sodium montmorilonite (Na‐MMt) was used as clay. Methylenebisacrylamide (MBA) and ammonium persulfate (APS) were used as crosslinker and initiator, respectively. The effect of reaction variables such as nanoclay content, MBA and APS concentrations as well as the AMPS/AAm weight ratio on the water absorbency of nanocomposites was investigated. Although the water absorbency was decreased by increasing of MBA concentration, an optimum swelling capacity was achieved for clay, APS, and AMPS/AAm variables. The structure of nanocomposite was identified using FTIR spectroscopy, XRD patterns, and scanning electron microscopy graphs. The effect of swelling media comprising various dissolved salts and different pHs was studied. Also, water retention capacity was studied, and the results showed that inclusion of Na‐MMt nanoclay causes an increase in water retention under heating. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Hydrolyzed collagen‐based hydrogel with salt and pH‐responsiveness properties

A novel hydrolyzed collagen‐based hydrogel has been prepared by grafting the binary mixture of acrylamide and 2‐acrylamido‐2‐methylpropanesulfonic acid onto the collagen backbone in the presence of a crosslinking agent. Its physicochemical properties in aqueous solution were studied. The effect of reaction variables on both gel content and swelling capacity was investigated to achieve a hydrogel with improved absorbency and gel content. The absorbency under load of optimized hydrogel was also investigated by using an absorbency under load tester at various applied pressures. The swelling ratio in various salt solutions was also determined and additionally, the swelling of hydrogels was measured in solutions with pH ranged 1–13. The synthesized hydrogel exhibited a pH‐responsiveness character so that a swelling‐collapsing pulsatile behavior was recorded at pH 2 and 8. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of functionalized acrylic‐acrylamide‐based superabsorbent gels

We have synthesized series of superabsorbent polymers (SAPs) by solution free radical polymerization of acrylic acid (AA), acrylamide (AM) with different functional monomers (FM). Three functional monomers including zwitterionic monomer [3‐(methacryloylamino) propyl] dimethyl (3‐sulfopropyl) ammonium (MPDSA), cationic monomer (3‐acrylamidopropyl) trimethylammonium chloride (APTAC) and anionic monomer 2‐acrylamidoglycolic acid monohydrate (AGAM) were selected to provide different charged groups on the superabsorbents. The effect of reaction parameters, such as degree of neutralization, content of initiator and crosslinker on the swelling capacity were assessed. The water absorbency of the superabsorbent were characterized in the distilled water, 0.9 wt % NaCl solution and the mixed solution containing 60 mg L^?1 CaCl₂ and 30 mg L^?1 MgCl₂, respectively. In addition, the swelling rate and water retention capacity in the soil were also investigated. Finally, the mechanism of different absorbency induced by the variety kinds of functional monomers was studied by XPS and FTIR, and tentative interpretation was presented as well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

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     

Modified carrageenan. 4. Synthesis and swelling behavior of crosslinked κC‐g‐AMPS superabsorbent hydrogel with antisalt and pH‐responsiveness properties

To synthesize a novel biopolymer‐based superabsorbent hydrogel, 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) was grafted onto kappa‐carrageenan (κC) backbones. The graft copolymerization reaction was carried out in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator, N,N,N′,N′‐tetramethyl ethylenediamine (TMEDA) as an accelerator, and N,N′‐methylene bisacrylamide (MBA) as a crosslinker. A proposed mechanism for κC‐g‐AMPS formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The affecting variables on swelling capacity, i.e., the initiator, the crosslinker, and the monomer concentration, as well as reaction temperature, were systematically optimized. The swelling measurements of the hydrogels were conducted in aqueous solutions of LiCl, NaCl, KCl, MgCl₂, CaCl₂, SrCl₂, BaCl₂, and AlCl₃. Due to the high swelling capacity in salt solutions, the hydrogels may be referred to as antisalt superabsorbents. The swelling of superabsorbing hydrogels was measured in solutions with pH ranging 1 to 13. The κC‐g‐AMPS hydrogel exhibited a pH‐responsiveness character so that a swelling–deswelling pulsatile behavior was recorded at pH 2 and 8. The overall activation energy for the graft copolymerization reaction was found to be 14.6 kJ/mol. The swelling kinetics of the hydrogels was preliminarily investigated as well. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 255–263, 2005     

Formulation design,optimization, characterization and swelling behaviour of a cationic superabsorbent based on a copolymer of [3‐(methacryloylamino)propyl]trimethylammonium chloride and acrylamide

A series of crosslinked copolymers with cationic nature have been prepared based on acrylamide (AAm) and [3‐(methacryloylamino)propyl]trimethyl ammonium chloride (MAPTAC) using N,N′ methylene‐bis‐acrylamide (MBA) as crosslinking agent. Taguchi's method has been employed for the purpose of formulation design and optimization as well as investigating the effects of various compositional parameters, such as total monomer concentration, cationic monomer and crosslinking agent concentration. The swelling behaviour of the synthesized gels in electrolyte solutions composed of ions with different valency has been studied and compared with an anionic‐based superabsorbent. The swelling capacity and absorbency were found to be enhanced with increase of the MAPTAC moieties of the copolymer chains, and therefore increase of their cationic character. All the cationic hydrogels prepared had greater swelling capacity, with less change in their swelling behaviour, when immersed into aqueous solutions containing multivalent cations. The anionic‐based hydrogels collapsed in similar ionic solutions with moderate‐to‐high ionic strength and did not show any tendency to re‐swell. The complex modulus (G*) of the crosslinked copolymers in the equilibrium swollen state was measured by rheomechanical spectroscopy and was correlated with the chemical composition of the network. Thermogravimetric analysis of the dry cationic superabsorbent showed more bound water but similar thermal behaviour to crosslinked polyacrylamide Copyright © 2003 Society of Chemical Industry     

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     

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     

Preparation of acrylated agarose‐based hydrogels and investigation of their application as fertilizing systems

In this study, we attempt to synthesize novel acrylated agarose (ACAG)‐based hydrogels with three different crosslinking densities. Acrylate groups were inserted onto agarose (AG) backbone through homogeneous reaction of acrylic monomers with AG backbone. Hydrogels were synthesized through radical copolymerization of a mixture of acrylic acid and 2‐hydroxyethyl acrylate with ACAG in aqueous solution using ammonium persulfate as an initiator. Infrared spectroscopy (FTIR) was carried out to confirm the chemical structure of the hydrogel. Moreover, morphology of the samples was assessed by scanning electron microscopy. The equilibrium swelling capacities of synthesized hydrogels were evaluated in various conditions. The absorbency under load and dynamic swelling kinetics of the hydrogels were also studied. Finally, the hydrogels were loaded with potassium nitrate and their potential for controlled release of this salt was investigated by conductimetry. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

A new composite sorbent for water and dye uptake: Highly swollen acrylamide/2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid/clay hydrogels crosslinked by 1,4‐butanediol dimethacrylate

A novel type of highly swollen hydrogels based on acrylamide (AAm) with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) and clay such as bentonite (Bent) crosslinked by 1,4‐butanediol dimethacrylate (BDMA) was prepared by free radical solution polymerization in aqueous media. Water uptake and dye sorption properties of polyelectrolyte AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels were investigated as a function of composition to find materials with swelling and sorption properties. FTIR analyses were made. Swelling experiments were performed in water and dye solution at 25°C, gravimetrically. Highly swollen AAm/AMPS and AAm/AMPS/Bent hydrogels were used in experiments on sorption of water‐soluble monovalent cationic dye such as Lauths violet “LV, (Thionin).” Swelling of AAm/AMPS hydrogels was increased up to 1,920–9,222% in water and 867–4,644% in LV solutions, while AAm hydrogels swelled 905% in water and swelling of AAm/AMPS/Bent hydrogels was increased up to 2,756–10,422% in water and 1,200–3,332% in LV solutions, while AAm/Bent hydrogels swelled 849% in water. Some swelling kinetic and diffusional parameters were found. Water and LV diffusion into hydrogels was found to be non‐Fickian in character. For sorption of cationic dye, LV into AAm/AMPS and AAm/AMPS/Bent hydrogel was studied by batch sorption technique at 25°C. The amount of the dye sorbed per unit mass removal effiency and partition coefficient of the hydrogels was investigated. The influence of AMPS content in the hydrogels to sorption was examined. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Preparation of starch‐graft‐poly(acrylamide)/attapulgite superabsorbent composite

A novel starch‐graft‐poly(acrylamide)/attapulgite superabsorbent composite was synthesized by graft copolymerization reaction of starch, acrylamide (AM), and attapulgite micropowder using N.N‐methylene‐bisacrylamide (MBA) as a crosslinker and ammonium persulphate (APS) as an initiator in aqueous solution, followed by hydrolysis with sodium hydroxide. The effects on water absorbency, such as amount of crosslinker, initiator, attapulgite, weight ratio of acrylamide to starch in the feed, gelatinization conditions of starch and molar ratio of NaOH to acrylamide, and so forth, were investigated. These superabsorbent composites were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The water absorbencies for these superabsorbent composites in water and saline solution were investigated, and water retention tests were carried out. Results obtained from this study showed that the water absorbency of superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10% exhibit absorption of 1317 g H₂O/g sample and 68 g H₂O/g sample in distilled water and in 0.9 wt % NaCl solution, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1351–1357, 2005     

Chitosan‐modified nanoclay–poly(AMPS) nanocomposite hydrogels with improved gel strength

BACKGROUND: Making (nano)composite structures is one of the efficient approaches for strengthening hydrogels extended in recent years. The present paper deals with the synthesis and properties of novel nanocomposite hydrogels based on 2‐acrylamido‐2‐methylpropane‐1‐sulfonic acid (AMPS). Initially, a bio‐modified clay, chitosan‐intercalated montmorillonite (chitoMMT), was prepared. Then, this was incorporated into the polymerization of AMPS in the presence of a macro‐crosslinker, i.e. poly(ethylene glycol) dimethacrylate, to yield super‐swelling nanocomposite hydrogels. The swelling capacity as well as some structural, rheological and thermomechanical properties of the hydrogels were studied and compared with those of the clay‐free counterpart. RESULTS: ChitoMMT exhibited no toxicity, which was confirmed using cell‐culture testing. A chitoMMT content of ca 6% was found to be the most favourable content of the bio‐modified clay for achieving a product with improved properties (i.e. the highest gel content, the highest gel strength and optimal thermal stability). Based on a dynamic mechanical thermal analysis study, an increased glass transition temperature (98.2 °C) and improved rubbery modulus (up to 238% higher than that of the clay‐free counterpart) were recorded. Thermogravimetric analysis verified that the thermal stability of nanocomposite samples was higher than that of clay‐free samples. CONCLUSION: Owing to the non‐toxicity of the incorporated chitoMMT, the strengthened hydrogels may be considered as potential candidates for bio‐applications. Copyright © 2009 Society of Chemical Industry     

Synthesis and properties of carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide) as a novel cellulose‐based superabsorbent

A new cellulose‐based superabsorbent polymer, carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide), was prepared by the free‐radical grafting solution polymerization of acrylic acid (AA) and acrylamide (AM) monomers onto carboxymethyl cellulose (CMC) in the presence of N,N′‐methylenebisacrylamide as a crosslinker with a redox couple of potassium persulfate and sodium metabisulfite as an initiator. The influences of reaction variables such as the initiator content, crosslinker content, bath temperature, molar ratio of AA to AM, and weight ratio of the monomers to CMC on the water absorbency of the carboxymethylcellulose‐graft‐poly(acrylic acid‐co‐acrylamide) copolymer were investigated. The copolymer's structures were characterized with Fourier transform infrared spectroscopy. The optimum reaction conditions were obtained as follows: the bath temperature was 50°C; the molar ratio of AA to AM was 3 : 1; the mass ratio of the monomers to CMC was 4 : 1; and the weight percentages of the crosslinker and initiator with respect to the monomers were 0.75 and 1%, respectively. The maximum water absorbency of the optimized product was 920 g/g for distilled water and 85 g/g for a 0.9 wt % aqueous NaCl solution. In addition, the superabsorbent possessed good water retention and salt resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1382–1388, 2007     

A Study of the Synthesis and Properties of AM/AMPS Copolymer as Superabsorbent

Summary: A new superabsorbent polymer, PAMA, has been prepared in an aqueous solution using acrylamide (AM) and 2‐acrylamido‐2‐methyl‐propanesulfonic acid (AMPS) as monomers, potassium persulfate (PPS) as initiator, and N,N′‐methylenebisacrylamide (NMBA) as cross‐linker. The absorbing properties and water retention of PAMA have been investigated. It is found that the absorbency of PAMA can reach 2 451 and 119 g · g^?1 in distilled water and in 0.9 wt.‐% NaCl solution, respectively. This copolymer also can absorb a large amount of pure methanol (277 g · g^?1), a property that has not been reported for the other superabsorbent polymers in the literature. The swelling behavior of PAMA in some water/organic solvent mixtures and water retention of PAMA in sand have been investigated.

Water retention of the PAMA in sand at 80 °C. 1) Sample containing PAMA; 2) Sample without PAMA.     

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     

Hybrid hydrogel based on pre-gelatinized starch modified with glycidyl-crosslinked microgel

Hybrid hydrogels based on pre-gelatinized starch were synthesized by inverse emulsion polymerization through modifying the starch with a glycidyl-crosslinked microgel. Glycidyl-crosslinked microgel is a special latex with high ability to impart hydrophilic characteristics to various substrates. Glycidyl-crosslinked microgel latexes with various structures were synthesized, and the effect of latex type on swelling capacity of the hybrid hydrogels based on pre-gelatinized starch was investigated. The highest swelling capacity was achieved for a pre-gelatinized starch modified with a glycidyl-crosslinked microgel latex based on poly(acrylic acid, sodium acrylate, acrylamide, 2-acrylamide-2 methyl propane sulfonic acid) (AA–SA–AM–AMPS). The swelling values of this hybrid hydrogel in distilled water and saline solution were 52.4 and 28.8 g/g, respectively. A key advantage of these hybrid hydrogels is that starch constitutes 64% of their structure. Given the fact that such hybrid hydrogels display low absorbency under load (AUL), they were surface crosslinked using microwave heating instead of conventional heating. Ethylene glycol diglycidyl ether was used as surface crosslinker. The AUL of the surface crosslinked hybrid hydrogels was increased by 85%. The hydrogels were characterized using FTIR, thermogravimetric analysis, scanning electron microscopy, and rheological measurements.     

pH sensitivity and swelling behavior of partially hydrolyzed formaldehyde-crosslinked poly(acrylamide) superabsorbent hydrogels

Poly(acrylamide) superabsorbent hydrogel was synthesized through crosslinking method. Formaldehyde was used as a crosslinking agent. To achieve a hydrogel with high swelling capacity, the resulted hydrogels were saponified using NaOH solution at high temperature. During saponification, ammonia gas is produced from hydrolysis reaction of amide groups. The arising of ammonia produces porous structure in hydrogels, which is confirmed using scanning electron microscopy. The conversion of amide groups to carboxylate groups was identified by FTIR spectroscopy. The reaction variables in both crosslinking and hydrolysis reactions that affect the swelling of hydrogels were optimized. The swelling of the hydrogels in various salt solutions with various valencies and radii was studied. Also, the absorbency under load was measured. The hydrogels exhibited pH-sensitivity characteristics. A sharp swelling change was observed in lieu of pH variations in a wide range (1–13). The swelling variations were explained according to the swelling theory based on the hydrogel chemical structure. The pH-reversibility and on–off switching behavior makes the intelligent hydrogels as good candidates for considering as potential drug carries. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

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