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     

Swelling behaviors of ionic poly(N,N‐dimethylacrylamide‐co‐acrylamide) hydrogels in various media

Polyelectrolyte hydrogels were synthesized from N,N‐dimethylacrylamide, acrylamide, and itaconic acid with ammonium persulfate as a free‐radical initiator in the presence of methylene(bis)acrylamide as a crosslinker. The swelling behavior of the ionic poly(N,N‐dimethylacrylamide‐co‐acrylamide) hydrogels was investigated in pure water, in KSCN solutions with pHs 4 and 9, and in water–acetone mixtures according to the itaconic acid content in the hydrogel. The pulsatile swelling behavior of these hydrogels was studied both in water–acetone and in pH 2–9 buffer solutions. Although the equilibrium swelling ratio of the hydrogels with low concentrations of itaconic acid was almost not affected by changes in the temperature, the equilibrium swelling ratio of the hydrogels with high concentrations of itaconic acid increased in the temperature range of 20–50°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2140–2145, 2007     

Swelling behavior and determination of diffusion characteristics of acrylamide–acrylic acid hydrogels

In this study, a random copolymer of acylamide and acrylic acid [poly(AAm‐co‐AA)] was prepared by a redox copolymerization method of their aqueous solutions. The effects of initial AAm/AA mole ratio, PEG 4000 content, and N,N′‐methylenebisacrylamide concentration on swelling behavior were investigated in water. Average molecular weights between crosslinks, percentage swelling, swelling equilibrium values, and diffusion/swelling characteristics (i.e., the structure of network constant, the type of diffusion, the initial swelling rate, swelling rate constant) were evaluated for every hydrogel systems. The hydrogels showed mass swelling capabilities in the range 789–1040% (for AAm/AA hydrogels), 769–930% (for AAm/AA hydrogels in the presence of PEG 4000), and 716–1040% (for AAm/AA hydrogels containing different concentrations of the crosslinker). The swelling capabilities of the hydrogels decreased with the increasing AA, PEG 4000, and crosslinker concentrations. The diffusion of water into AAm/AA hydrogels was found to be a non‐Fickian type. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1289–1293, 2004     

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     

pH‐sensitive dimethylaminoethyl methacrylate (DMAEMA)/acrylamide (AAm) hydrogels: Synthesis and adsorption from uranyl acetate solutions

A random copolymer of dimethylaminoethyl methacrylate (DMAEMA) and acrylamide(AAm) [poly(DMAEMA/AAm)], with a pH‐sensitive character, was prepared by a redox polymerization method. Increasing the DMAEMA content of the gel, the pH, and the ionic strength of the solution decreased the swelling ratios of the hydrogels. The adsorption of poly(DMAEMA/AAm) hydrogels from uranyl acetate (UA) solutions was studied at different pHs. The adsorption capacity of hydrogels increased from 200 to 1200 mg of UA per gram of dry hydrogel with increasing pH of the adsorption solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2028–2031, 2003     

Preparation and swelling behavior of macroporous poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels

Macroporous superabsorbent hydrogels (SAHs) composed of acrylamide (AAm) and sodium methacrylate (NMA) were prepared by aqueous solution polymerization in the presence of a glucose solution. Their swelling capacity was investigated as a function of the concentrations of the glucose solution, sodium methacrylate, crosslinker, initiator, and activator. The porosity of the poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels was confirmed using scanning electron microscopy. The SAHs were characterized by IR spectroscopy. To estimate the effect on the swelling behavior, three types of crosslinkers were employed: N,N′‐methylenebisacrylamide, 1,4‐butanediol diacrylate, and diallyl phthalate. Network structural parameters such as initial swelling rate, swelling rate constant, and maximum equilibrium swelling were evaluated by water absorption measurement. The equilibrium water content (EWC%) of the AAm–NMA macroporous SAHs was found to be in the range of 93.31–99.68, indicating that these SAHs may have applications as biomaterials in the medicinal, pharmaceutical, and veterinary fields. Most of the SAHs prepared in this investigation followed non‐Fickian‐type diffusion, and few followed a case II– or super–case II‐type diffusion. The diffusion coefficients of these macroporous SAHs were investigated. Further, the swelling behavior of these SAHs also was investigated at different pHs and in different salt solutions and simulated biological fluids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3202–3214, 2006     

Environmentally sensitive hydrogels: N‐isopropyl acrylamide/Acrylamide/ Mono‐, Di‐, Tricarboxylic acid crosslinked polymers

Environmentally sensitive hydrogels responsive to various stimuli such as temperature, pH, ionic strength of the medium and the solvent were prepared by using N‐isopropyl acrylamide (NIPAM), acrylamide (AAm) and monomers that have various number of carboxylic acid (XA) functionality using N,N′‐methylene bisacrylamide (Bis) as crosslinker. Hydrogels were prepared via free radical polymerization reaction in aqueous solution. P(NIPAAm‐co‐AAm) and p(NIPAAm‐co‐AAm)/XA hydrogels that contain monoprotic crotonic acid (CA) exhibit a lover critical solution temperature (LCST) at 28°C, whereas p(NIPAAm‐co‐AAm)/IA (IA:itaconic acid), and P(NIPAAm‐co‐AAm)/ACA (ACA:acotonic acid) hydrogels exhibit a lover critical solution temperature at 30.7°C and 34.4°C, respectively. Spectroscopic and thermal analyses were performed for the structural and thermal characterizations of the prepared hydrogel. The swelling experiments as equilibrium swelling percentages by gravimetrically were carried out in different solvents, at different solutions temperature, pH, and ionic strengths to determine their effects on swelling characteristic of hydrogels. POLYM. ENG. SCI., 55:843–851, 2015. © 2014 Society of Plastics Engineers     

Temperature/pH/magnetic triple‐sensitive nanogel–hydrogel nanocomposite for release of anticancer drug

Hydrogels, nanogels and nanocomposites show increasing potential for application in drug delivery systems due to their good chemical and physical properties. Therefore, we were encouraged to combine them to produce a new compound with unique properties for a long‐term drug release system. In this regard, the design and application of a nanocomposite hydrogel containing entrapped nanogel for drug delivery are demonstrated. To this aim, we first prepared an iron oxide nanocomposite nanogel based on poly(N‐isopropylacrylamide)‐co‐((2‐dimethylaminoethyl) methacrylate) (PNIPAM‐co‐PDMA) grafted onto sodium alginate (NaAlg) as a biocompatible polymer and iron oxide nanoparticles (ION) as nanometric base (PND/ION‐NG). This was then added into a solution of PDMA grafted onto NaAlg. Through dropwise addition of mixed aqueous solution of iron salts into the prepared polymeric solution, a novel hydrogel nanocomposite with excellent pH, thermal and magnetic responsivity was fabricated. The synthesized samples were fully characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy with energy‐dispersive X‐ray analysis, vibrating sample magnetometry and atomic force microscopy. A mechanism for the formation of PNIPAM‐co‐PDMA/NaAlg‐ION nanogel–PDMA/NaAlg‐ION hydrogel and PND/ION nanogel is suggested. Swelling capacity was measured at various temperatures (25 to 45 °C), pH values (from 2 to 11) and magnetic field and under load (0.3 psi) and the dependence of swelling properties of the nanogel–hydrogel nanocomposite on these factors was well demonstrated. The release rate of doxorubicin hydrochloride (DOX) as an anticancer drug was studied at different pH values and temperatures in the presence and absence of a magnetic field. The results showed that these factors have a high impact on drug release from this nanocomposite. The result showed that DOX release could be sustained for up to 12.5 days from these nanocomposite hydrogels, significantly longer than that achievable using the constituent hydrogel or nanogel alone (<1 day). The results indicated that the nanogel–hydrogel nanocomposite can serve as a novel nanocarrier for anticancer drug delivery. © 2019 Society of Chemical Industry     

Synthesis and swelling behavior of thermosensitive IPN hydrogels based on sodium acrylate and N‐isopropyl acrylamide by a two‐step method

A series of interpenetrating polymer network (IPN) hydrogels having higher swelling ratio (SR) and thermosensitivity were synthesized from sodium acrylate (SA) and N‐isopropyl acrylamide (NIPAAm) by a two‐step method. A series of the porous poly(sodium acrylate ‐co‐1‐vinyl–2‐pyrrolidone) [poly(SA‐co‐VP)], (SV), hydrogels were prepared from acrylic acid having 90% degree of neutralization and VP monomer in the first step. The second step is to immerse the SV dried gels into the NIPAAm solution containing initiator, accelerator, and crosslinker to absorb NIPAAm solution and then polymerized to form the poly(SA‐co‐VP)/poly(NIPAAm) IPN hydrogels (SVN). The effect of the different molar ratios of SA/VP and the content of NIPAAm on the swelling behavior and physical properties of the SVN hydrogels was investigated. Results showed that the SVN hydrogels displayed an obviously thermoreversible behavior when the temperature turns across the critical gel transition temperature (CGTT) of poly(NIPAAm) hydrogel. The pore diameter distributions inside the hydrogel also indicated that the pore sizes inside the SVN hydrogels were smaller than those inside the SV hydrogels. At the same time, the more proportion of SA was added into the hydrogel, the larger pore diameter of the SV hydrogel was formed. The results also showed that the SR decreased with an increase of the VP content in the SV hydrogel and more obviously decreased in the SVN hydrogels. The SVN networks also showed stronger shear moduli than SV hydrogels. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Swelling behavior of thermoreversible poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) hydrogels

Thermoresponsive hydrogels based on N‐isopropylacrylamide and N‐vinylimidazole were synthesized, and their swelling–deswelling behavior was studied as a function of the total monomer concentration. For copolymeric structures with better thermoresponsive properties with respect to poly(N‐isopropylacrylamide‐co‐N‐vinylimidazole) hydrogels, these hydrogels were protonated with HCl and HNO₃, and the copolymer behaviors were compared with those of the unprotonated hydrogels. The temperature was changed from 4 to 70°C at fixed pHs and total ionic strengths. The equilibrium swelling ratio, dynamic swelling ratio, and dynamic deswelling ratio were evaluated for all the hydrogels. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1619–1624, 2004     

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     

Ethanol‐assisted dispersion of attapulgite and its effect on improving properties of alginate‐based superabsorbent nanocomposite

The dispersion of attapulgite (APT) as nanorod‐like single crystals is crucial to fully develop its functionality of one‐dimensional nanometer material as a filler of composite materials. In this study, APT was dispersed by the assistance of ethanol during the high‐pressure homogenization process to form individual nanorod‐like crystals. The dispersed APT was used to prepare new sodium alginate‐g‐poly(sodium acrylate‐co‐styrene)/attapulgite (NaAlg‐g‐P(NaA‐co‐St)/APT) superabsorbent nanocomposites. The effect of ethanol/water ratio on the dispersion of crystal bundles of APT was investigated by field emission scanning electron microscopy, and the results indicate that APT crystal bundles were effectively disaggregated in ν(CH₃CH₂OH) : ν(H₂O) ? 5 : 5 solution after homogenized at 50 MPa. The better dispersion of APT in NaAlg‐g‐P(NaA‐co‐St) matrix has clearly improved the gel strength (from 1300 Pa to 1410 Pa, ω = 100 rad/s), swelling capacity (442–521 g/g), swelling rate (3.3303–4.5736 g/g/s), and reswelling ability of the superabsorbent nanocomposite. Moreover, the nanocomposites showed fast swelling–deswelling responsive behavior in different saline solutions. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) hydrogels: Interactions with surfactants

Poly(N‐isopropylacrylamide‐co‐sodium acrylate) [poly(NIPAM‐co‐SA)] hydrogels were modified with three different kind of surfactants (cationic, anionic, and nonionic) to study the effect on the swelling properties. The structural variation of the surfactant‐modified hydrogels was investigated in detail. The interaction between the surfactants and the hydrogel varies and strictly depends on the surfactant type. The variation in thermal stability of the modified surfactant hydrogels was investigated and compared with unmodified hydrogel. Further, the hydrogel swelling/diffusion kinetic parameters were investigated and diffusion of water into hydrogel was found to be of the non‐Fickian transport mechanism. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3423–3430, 2007     

The usability of (sodium alginate/acrylamide) semi-interpenetrating polymer networks on removal of some textile dyes

In this study, (sodium alginate/acrylamide) interpenetrating polymer networks ((NaAlg/AAm)IPN) have been prepared at definite composition. The aqueous solution of 3% (w/v) sodium alginate and 50% (w/v) acrylamide was irradiated with ⁶⁰Co-γ rays at a dose rate of 0.07 kGy/h up to 5 kGy. The percent conversion was determined gravimetrically and 100% gelation was achieved at 5 kGy dose. To understand whether the semi-interpenetrating polymer network of sodium alginate is performed, Fourier Transform Infrared (FTIR) spectra of polyacrylamide (PAAm), sodium alginate, and the semi-interpenetrating polymer network were recorded. It is found that the FTIR spectra of PAAm, NaAlg, and the semi-interpenetrating polymer network are different. The thermograms of PAAm, sodium alginate, and the semi-interpenetrating polymer network were recorded for investigating their thermal character. (NaAlg/AAm)IPN hydrogels were immersed to swell in a solution of pH 7, at a temperature of 25°C. The swelling results at pH 7.0 indicated that (NaAlg/AAm)IPN hydrogel, containing 3% NaAlg showed maximum % swelling in water but swelling increased in the order of water > Magenta > Methylene Blue > Safranine-O > Methyl Violet. Diffusion of water and aqueous solution of dyes within (NaAlg/AAm)IPN hydrogels was found to be of Fickian character at the initial stage of swelling with regard to values calculated for diffusion coefficient of (NaAlg/AAm)IPN hydrogels in water and aqueous solution of dyes. Some diffusion parameters were calculated from swelling of (NaAlg/AAm)IPN in water and dyes and their adsorption isotherms were plotted. In the adsorption experiments, the efficiency of (NaAlg/AAm)IPN hydrogels to adsorb Magenta, Safranine-O, Methylene Blue, and Methyl Violet dyes from water was studied. (NaAlg/AAm)IPN hydrogels showed different adsorption for different aqueous solution of dyes at pH 7.0. Adsorption isotherms were constructed for (NaAlg/AAm)IPN-dye systems. S type adsorption in the Giles classification system was found. Thermal and spectroscopic characterization of semi-interpenetrating polymer network of sodium alginate and acrylamide and dye adsorbed semi-interpenetrating polymer network of sodium alginate and acrylamide was recorded. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Swelling behavior of poly(acrylamide‐co‐N‐vinylimidazole) hydrogels under different environment conditions

A series of random copolymers of acrylamide and N‐vinylimidazole, poly(AAm‐co‐NVI), with various compositions were prepared using redox copolymerization. The influence of environmental conditions such as pH, temperature, and ionic strength on the swelling behavior of the copolymeric hydrogels was investigated. The hydrogels exhibited the highest equilibrium swelling in basic medium at high temperature. Equilibrium swelling decreased with rising ionic strength at pH 5.0. As pH increased, equilibrium swelling of the hydrogels increased at pH 11.0 and I = 0.20 M. Swelling kinetics of the hydrogels was found to be non‐Fickian at 25°C. The process tended to be Fickian at higher pH and temperature. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1783–1788, 2005     

Preparation of alginate/poly(N‐isopropylacrylamide) semi‐interpenetrating and fully interpenetrating polymer network hydrogels with γ‐ray irradiation and their swelling behaviors

Semi‐interpenetrating polymer network (semi‐IPN) and fully interpenetrating polymer network (full‐IPN) hydrogels composed of alginate and poly(N‐isopropylacrylamide) were prepared with γ‐ray irradiation. The semi‐IPN hydrogels were prepared through the irradiation of a mixed solution composed of alginate and N‐isopropylacrylamide (NIPAAm) monomer to simultaneously achieve the polymerization and self‐crosslinking of NIPAAm. The full‐IPN hydrogels were formed through the immersion of the semi‐IPN film in a calcium‐ion solution. The results for the swelling and deswelling behaviors showed that the swelling ratio of semi‐IPN hydrogels was higher than that of full‐IPN hydrogels. A semi‐IPN hydrogel containing more alginate exhibited relatively rapid swelling and deswelling rates, whereas a full‐IPN hydrogel showed an adverse tendency. All the hydrogels with NIPAAm exhibited a change in the swelling ratio around 30–40°C, and full‐IPN hydrogels showed more sensitive and reversible behavior than semi‐IPN hydrogels under a stepwise stimulus. In addition, the swelling ratio of the hydrogels continuously increased with the pH values, and the swelling processes were proven to be repeatable with pH changes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4439–4446, 2006     

Nanocomposite hydrogels for selective removal of cationic dyes from aqueous solutions

Removal of organic dyes from waste water has received a significant attention in recent years. In this work, a set of nanocomposite hydrogels (NHs) were prepared and their capacity to absorb crystal violet (CV), a cationic dye, and acid yellow‐23 (AY), an anionic dye, from aqueous solutions was determined. NHs were prepared by in situ formation of Fe₃O₄ magnetic nanoparticles (MNPs) inside poly(acrylamide‐co‐4‐styrene sulfonic acid sodium salt) (P[AAm‐co‐SSA]) hydrogel matrices. The dye absorption capacity of the magnetic NHs (MNHs) was compared with simple hydrogels (hydrogels or SHs) without the MNPs The prepared hydrogels were characterized by FTIR, XRD, thermogravimetric analysis, high resolution TEM, field emission SEM, and vibrating sample magnetometer measurement. From HRTEM, it was confirmed that the prepared MNPs in hydrogel matrices were in the size range of about 8 to 10 nm. The MNHs showed greater swelling behavior as well as greater removal efficiency of cationic dye from aqueous solutions in comparison to the SHs. With increase of SSA mole percentage, dye removal efficiency was also increased for both types of hydrogels. The present study indicates that the hydrogels containing MNPs can be potentially used as an efficient absorbent material for removal of cationic dyes from waste water. POLYM. ENG. SCI., 56:776–785, 2016. © 2016 Society of Plastics Engineers     

Swelling behavior of semi‐interpenetrating polymer network hydrogels composed of poly(vinyl alcohol) and poly(acrylamide‐co‐sodium methacrylate)

Interpenetrating polymer network (IPN) hydrogels based on poly(vinyl alcohol) (PVA) and poly(acrylamide‐co‐sodium methacrylate) poly(AAm‐co‐SMA) were prepared by the semi IPN method. These IPN hydrogels were prepared by polymerizing aqueous solution of acrylamide and sodium methacrylate, using ammonium persulphate/N,N,N¹,N¹‐tetramethylethylenediamine (APS/TMEDA) initiating system and N,N¹‐methylene‐bisacrylamide (MBA) as a crosslinker in the presence of a host polymer, poly(vinyl alcohol). The influence of reaction conditions, such as the concentration of PVA, sodium methacrylate, crosslinker, initiator, and reaction temperature, on the swelling behavior of these IPNs was investigated in detail. The results showed that the IPN hydrogels exhibited different swelling behavior as the reaction conditions varied. To verify the structural difference in the IPN hydrogels, scanning electron microscopy (SEM) was used to identify the morphological changes in the IPN as the concentration of crosslinker varied. In addition to MBA, two other crosslinkers were also employed in the preparation of IPNs to illustrate the difference in their swelling phenomena. The swelling kinetics, equilibrium water content, and water transport mechanism of all the IPN hydrogels were investigated. IPN hydrogels being ionic in nature, the swelling behavior was significantly affected by environmental conditions, such as temperature, ionic strength, and pH of the swelling medium. Further, their swelling behavior was also examined in different physiological bio‐fluids. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 302–314, 2005     

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     

Swelling and Adsorption Properties of Hydrophobic Poly[(N‐(3‐(dimethylamino)propyl)methacrylamide)‐co‐(lauryl acrylate)] Hydrogels in Aqueous Solutions of Surfactants

Summary: The swelling and adsorption behavior of a series of hydrophobic poly[(N‐(3‐(dimethylamino)propyl)methacrylamide)‐co‐(lauryl acrylate)] [P(DMAPMA‐co‐LA)] hydrogels was studied as a function of temperature in aqueous solutions of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant dodecyltrimethylammonium bromide (DTAB). Between 0 and 41.7 mol‐% of lauryl acrylate (LA) were used as a hydrophobic comonomer in the hydrogel synthesis. In SDS solutions, the equilibrium swelling ratio of the hydrogels decreased with increasing temperature. At SDS concentrations below 0.0083 M , the hydrogels exhibited an almost linear swelling behavior. However, for SDS concentrations above 0.0083 M , non‐linear swelling behavior was observed in the range 28–36 °C. In contrast to the SDS solutions, in all DTAB solutions the equilibrium swelling ratio of the hydrogels increased with increasing temperature and a positive temperature sensitive property was shown for all P(DMAPMA‐co‐LA) hydrogels. The adsorption capacities of the hydrogels in aqueous solutions of SDS and DTAB were determined via surface tension measurements. An increase in the LA content in the hydrogel caused an increase in the amount of adsorbed surfactant molecules in both media.

Effect of the DTAB concentration on the adsorption capacities of P(DMAPMA‐co‐LA) hydrogels.