Equilibrium swelling studies of highly swollen acrylamide/mesaconic acid hydrogels

Acrylamide/mesaconic acid (AAm/MA) hydrogels were prepared by free radical solution polymerization in aqueous solution of acrylamide (AAm) with mesaconic acid (MA) as comonomer and two multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4‐butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. The influence of mesaconic acid content in hydrogels was examined. Swelling of AAm/MA hydrogels was increased up to 2301% (for containing 20 mg MA and crosslinked by EGDMA) to 3296% (for containing 80 mg MA and crosslinked by BDMA), while AAm hydrogels swelled up to 1330% (crosslinked by BDMA) to 1400% (crosslinked by EGDMA). The values of equilibrium water content of the hydrogels are 0.9301–0.9706. Diffusion behavior was investigated. Water diffusion into hydrogels was found to be non‐Fickian in character. Diffusion coefficients of AAm/MA hydrogels were calculated by the short time approximation and found to be from 38.01 × 10^?6 cm² s^?1 to 182.73 × 10^?6 cm² s^?1. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2253–2259, 2005     

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     

Behaviors of Chemically Crosslinked CAAMPS Hydrogels in Uptake of Uranyl Ions from Aqueous Solutions

Uranyl ion adsorption from aqueous solutions has been investigated by chemically crosslinked (C) polyelectrolyte acrylamide/2-acrylamido-2-methyl-1-propanesulfonic acid (CAAMPS) hydrogels. CAAMPS hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), and water by free radical polymerization in an aqueous solution using multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4 butanediol dimethacrylate (BDMA). The swelling equilibrium of polyelectrolyte copolymer gels containing of CAAMPS hydrogels has been studied as a function of copolymer composition. Swelling experiments were performed in water at 25°C, gravimetrically. The influence of AMPS content in hydrogels was examined. The weight-swelling ratio of CAAMPS hydrogels was increased up to 127.03 (for 300 mg AMPS and crosslinked by EGDMA) and 93.32 (for 300 mg AMPS and crosslinked by BDMA), while acrylamide hydrogels swelled up to 10.27 (crosslinked by EGDMA) and 10.06 (crosslinked by BDMA). Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of AMPS on the uranyl ion adsorption were examined. In the experiments of the sorption, L type sorption in the Giles classification system was found. Finally, the amount of sorbed uranyl ion per gram of dry hydrogel (q) was calculated to be 0.67 × 10^?3–2.11 × 10^?3 mol uranyl ion per gram for CAAMPS hydrogels. Removal effiency of uranyl ions (RE%) was changed range 9.05–29.92%. The values of partition ratio, (K _d ) of uranyl ions was calculated to be 0.10–0.43 for CAAMPS hydrogels.     

Water Sorption and Dye Uptake Studies of Highly Swollen AAm/AMPS Hydrogels and Semi-IPNs with PEG

A semi-interpenetrating network (semi-IPNs) hydrogel, composed of acrylamide (AAm) with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) as co-monomer, with poly(ethylene glycol) (PEG) and two multifunctional cross-linkers such as 1,4-butanediol dimethacrylate (BDMA), and trimethylolpropane triacrylate (TMPTA) was prepared. AAm/AMPS hydrogels and AAm/AMPS/PEG semi-IPNs were synthesized by free radical solution polymerization. Swelling experiments were performed in water at 25°C, gravimetrically. For sorption of Toluidin Blue (Basic Blue 17, TB) into AAm/AMPS hydrogels and AAm/AMPS/PEG semi-IPNs was studied by batch sorption technique at 25°C. Dye removal capacity, removal effiency and partition coefficient of the hydrogels was investigated.     

Behaviors of polyelectrolyte AAm/AMPS/bentonite composite hydrogels in uptake of uranyl ions from aqueous solutions

Uranyl ion (UO₂²⁺) sorption properties of polyelectrolyte composite hydrogels made by the polymerization of acrylamide (AAm) with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) and clay such as bentonite (Bent) were investigated as a function of composition to find materials with swelling and uranyl ion sorption properties. Highly swollen AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with AMPS as co‐monomer and two multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4 butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. The influence of AMPS content in hydrogels was examined. Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of AMPS on the uranyl ion adsorption were examined. Finally, adsorption capacity (the amount of sorbed uranyl ion per gram of dry hydrogel) (q) was calculated to be 0.67 × 10⁻³–2.11 × 10⁻³ mol uranyl ion per gram for the hydrogels. Removal effiency of uranyl ions (RE%) was changed range 9.05–29.92%. The values of partition ratio (K_d) of uranyl ions was calculated to be 0.10–0.43 for AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels, respectively. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Swelling characterization of poly (acrylamide-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">N</Emphasis>-vinylimidazole) hydrogels crosslinked by TMPTA and semi-IPN’s with PEG

In this study, a novel semi-interpenetrating network (semi-IPN’s) hydrogel, composed of acrylamide (AAm) with N-vinylimidazole (NVI) as comonomer, with poly (ethylene glycol)(PEG) and a multifunctional crosslinker such as trimethylolpropane triacrylate (TMPTA) was prepared. Highly swollen poly (AAm/NVI) hydrogels and semi-IPN’s were synthesized by free radical solution polymerization. Swelling experiments were performed in water at 25°C, gravimetrically. The influence of NVI and PEG content in hydrogels were examined. Poly (AAm/NVI) and poly (AAm/NVI/PEG) hydrogels showed large extents of swelling in aqueous media the swelling being highly dependent on the chemical composition of the hydrogels. Swelling ratio of poly (AAm/NVI) hydrogels and poly (AAm/NVI/PEG) hydrogels was shown 7.16–39.85. Diffusion behavior was investigated. Water diffusion into hydrogels was found to be non-Fickian in character. This study has given the quantitative information on the swelling characteristic of poly (AAm/NVI) hydrogel and semi-IPN’s as water absorbent in many potential applications.     

Equilibrium Swelling Studies of Chemically Cross-Linked Highly Swollen Acrylamide-Sodium Acrylate Hydrogels in Various Water-Solvent Mixtures

Swelling behavior of acrylamide (AAm)/sodium acrylate (SA) hydrogels was investigated in water-solvent (methanol, ethanol, t-butanol and acetone) mixtures of various compositions. AAm/SA hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with SA as comonomers and a multifunctional cross-linker such as trimethylolpropane triacrylate (TMPTA). Swelling experiments were performed in water and water-organic solvent mixtures of various compositions at 25°C, gravimetrically. The value of S_eq% of AAm/SA hydrogels are 64–152% for 60% of metanol, 84–102% for 60% of ethanol, 127–176% for 60% of t-butanol, 131–585% for 60% of acetone, while the value of S_eq% of AAm/SA hydrogels are 780–4510% for water and water-solvent mixtures. Some swelling kinetic parameters were found. Diffusion behavior of water and water-solvent mixtures was investigated. Diffusion of water and water-solvent mixtures into the hydrogels was found to be non-Fickian in character.     

Swelling studies of super water retainer acrylamide/crotonic acid hydrogels crosslinked by trimethylolpropane triacrylate and 1,4-butanediol dimethacrylate

Summary Superswelling acrylamide/crotonic acid (AAm/CA) hydrogels were prepared by free radical polymerization in aqueous solution of acrylamide (AAm) with crotonic acid (CA) as comonomer. For each copolymerization, four different composition of CA and a concentration of multifunctional crosslinkers such as trimethylolpropane triacrylate (TMPTA) and 1,4-butanediol dimethacrylate (BDMA) were used. As a result of dynamic swelling tests, the influence of the crosslinkers and the relative content of CA on the swelling properties were examined. AAm/CA hydrogels were swelled in the range of 1520–2980% in water, while AAm hydrogels swelled as 780 and 1360%. Equilibrium water content of AAm/CA hydrogels was calculated in the range of 88.73 and 96.75%. Water uptake of hydrogels was followed non-Fickian type diffusion. Received: 27 May 2001/Revised version: 8 January 2002/ Accepted: 27 March 2002     

A New Sorbent Chemically Cross-linked Highly Swollen Copolymeric Hydrogels for Dye Uptake

Water uptake and the sorption properties of polyelectrolyte hydrogels made by the polymerization of acrylamide (AAm) with maleic acid (MA) were investigated as a function of composition to find materials with swelling and dye sorption properties. Highly swollen acrylamide/maleic acid (AAm/MA) hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with MA as comonomer and two multifunctional cross-linkers such as trimethylolpropane triacrylate (TMPTA) and 1,4-butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. Chemically cross-linked AAm/MA hydrogels were used in experiments on sorption of water-soluble monovalent cationic dyes such as “Nil blue” (NB) and “Methyl violet (MV)”. Weight-swelling ratio values of AAm/MA hydrogels were calculated range 8.88–61.46. Some swelling kinetic parameters were found. Diffusion behavior of water and water sorption rate constant were investigated. Water diffusion into hydrogels was found to be non-Fickian in character. For sorption of cationic dyes, NB and MV into AAm/MA hydrogels were studied by batch sorption technique at 25°C. AAm/MA hydrogels in the dye solutions showed coloration. However, the AAm hydrogel did not show sorption of any dye from solution. The amount of the dye sorbed per unit mass of AAm/MA hydrogels was investigated.     

Swelling Characterization and Adsorptive Features of Acrylamide/Itaconic Acid Hydrogels and Semi-IPNs for Uranyl Ions

A novel semi-interpenetrating network (semi-IPNs) hydrogel, composed of acrylamide (AAm) with itaconic acid (ITA) as co-monomer, with poly (ethylene glycol)(PEG) and trimethylolpropane triacrylate (TMPTA) was prepared. Hydrogels and semi-IPNs were synthesized by free radical solution polymerization. Swelling experiments were performed in water and aqueous solutions of uranyl acetate. Diffusion behavior was investigated and their diffusion into hydrogels was found to be non-Fickian in character. Sorption of uranyl ion onto the polymeric system was studied by a batch sorption technique at 25°C. The sorption capacity, removal effiency and partition coefficient of the hydrogels were investigated.     

Swelling behavior and diffusion studies of high‐water‐retaining acrylamide/potassium methacrylate hydrogels

Poly(acrylamide‐co‐potassium methacrylate) hydrogels were prepared by free‐radical simultaneous polymerization with aqueous solutions of acrylamide (AAm) and potassium methacrylate (KMA) with a redox initiator. The copolymerization was performed with eight different compositions of KMA at a fixed concentration of oil‐soluble crosslinkers, including 1,4‐butanediol diacrylate and ethylene glycol dimethacrylate (EGDMA). For every composition of AAm/KMA copolymer, the percentage swelling, swelling equilibrium, and diffusion characteristics were investigated. The copolymers were further studied for deswelling properties. The power law relationships of the hydrogels were evaluated for variation in terms of saline concentration. The AAm/KMA copolymers were confirmed by IR spectroscopy. Thermal studies of hydrogels were performed with differential scanning calorimetry and thermogravimetric analysis. EGDMA was found to be a better crosslinker for obtaining higher swelling and deswelling properties for the AAm/KMA hydrogels. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1153–1164, 2005     

Dynamic and equilibrium swelling studies: crosslinked pH sensitive methyl methacrylate-co-itaconic acid (MMA-co-IA) hydrogels

In the present work crosslinked methyl methacrylate-co-itaconic acid (MMA-co-IA) hydrogels were prepared by free radical copolymerization of methyl methacrylate (MMA) with itaconic acid (IA) using ethylene glycol dimethacrylate (EGDMA) and N, N methylene bisacrylamide (MBAAm) as crosslinkers and benzoyl peroxide as initiator. Prepared hydrogels were investigated for dynamic and equilibrium swelling studies. For swelling behaviour, effect of pH, monomeric compositions, degree of crosslinking and type of crosslinking agent were investigated. Swelling studies were performed in the USP phosphate buffer solutions of varying pH 1.2, 4.5, 5.5, 6.5 and 7.0. Results showed that swelling increased by increasing IA content in hydrogels structure. This may be due to the presence of more carboxylic groups available for ionization. Swelling was decreased with increase in crosslinking ratio owing to tighter hydrogel structure. Hydrogels were characterized by Fourier transform infrared (FTIR), and scanning electron microscope (SEM). Polymer-solvent interaction parameters (χ) of hydrogels were determined by using Flory–Rehner theory of equilibrium swelling values. The analysis of diffusion mechanism from gels using Peppas model showed that all monomeric compositions and degrees of crosslinking followed Fickian diffusion.     

Removal of hazardous by radiation‐synthesized copolymer hydrogels based on 2‐acrylamido‐2‐methylpropanesulfonic acid and 2‐dimethyaminoethyl methacrylate monomers

Superabsorbent copolymer hydrogels were prepared by gamma irradiation of aqueous solutions of 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) and 2‐dimethyaminoethyl methacrylate (DEMA) monomers mixtures. The thermal stability of hydrogels was evaluated by thermogravimetric analysis. The ability to adsorb Cu²⁺ ions and dyes by the prepared hydrogels from aqueous solutions was investigated. The swelling study, in water, showed that the hydrogels based on pure AMPS monomer and AMPS/DEMA copolymers reached the equilibrium state after 6 h. However, the hydrogel based on pure AMPS monomer showed higher swelling than the copolymer hydrogels based on AMPS/DEMA. It was found that the copolymer hydrogels based on different compositions showed affinity to absorb Cu²⁺ metal ions as well as basic and acid dyes; however, this affinity was found to decrease with increasing the ratio of DEMA in the initial feeding solutions. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Preliminary swelling and dye sorption studies of acrylamide/4-styrenesulfonic acid sodium salt copolymers and semi-interpenetrating polymer networks composed of gelatin and/or PEG

Semi-IPN hydrogels based gelatin (GEL) and/or poly (ethylene glycol) (PEG) were prepared with acrylamide (AAm) and 4-styrenesulfonic acid sodium salt, (SSS) as a water adsorbent for cationic dye (methyl violet, MV) sorption. For this, chemically crosslinked copolymer of AAm/SSS copolymer with GEL and/or PEG were prepared by polymerization of aqueous solution of AAm and SSS using ammonium persulfate (APS)/N,N,N′,N′-tetramethylethylenediamine (TEMED) as redox initiating pair in presence of poly(ethylene glycol)diacrylate (PEGDA) as crosslinker. FT-IR analysis was used to identify the presence of different repeating units in the semi-IPNs. Surface morphology was characterized by scanning electron microscopy (SEM). Some swelling and diffusion characteristics were calculated for different semi-IPNs and hydrogels prepared under various formulations. Water uptake, and dye sorption properties of the crosslinked polymeric systems such as AAm/SSS, AAm/GEL/SSS, AAm/PEG/SSS and AAm/GEL/PEG/SSS hydrogel systems were investigated as a function of chemical composition of the hydrogels. MV have used in sorption studies.     

Synthesis, characterization and protein separation efficiency of N-isopropylacrylamide-co-N-tertiary butylacrylamide-co-acrylamide-based hydrogels

In the present study, hydrogels were prepared by free radical polymerization in water?Cdioxane mixture with fixed molar ratio (25?mol%) of N-isopropylacrylamide (NIPAM) and varying remaining molar concentrations of N-tert-butylacrylamide (NTBA) and acrylamide (AAm). The structure of the resultant hydrogels was studied by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques. The thermal properties of the hydrogels were analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. DSC thermograms were used for the quantitative determination of free, interfacial and bound water contents. The result showed that the free and interfacial water contents increased with increase in the hydrophilic AAm content, and the bound water content increased with hydrophobic NTBA content in the hydrogels. Swelling behavior of the hydrogels was evaluated at different temperatures. The percentage swelling and diffusion kinetic parameters (network structure constant, type of diffusion and diffusion constant) were calculated for all samples. The diffusion was found to be Fickian type for copolymer having equimolar concentrations of NTBA and AAm and non-Fickian type for others. Diffusion coefficients of the hydrogels were found to be increased with increasing temperature. In addition, poly(NIPAM-co-NTBA-co-AAm) hydrogels were used in concentration separation process for BSA solution. The result showed that the copolymer with equimolar NTBA and AAm contents has high separation efficiency with good thermoresponsive behavior among all copolymers.     

Swelling and dye sorption studies of AAm/SA hydrogels crosslinked by glutaraldehyde and divinylbenzene

Highly swollen acrylamide (AAm)/sodium acrylate (SA) hydrogels were prepared by free radical solution polymerization in aqueous solution of AAm with SA as comonomer and two multifunctional crosslinkers such as glutaraldehyde (GL) and divinylbenzene (DVB). Water absorption and percentage swelling were determined gravimetrically. The influence of SA content in hydrogels was examined. Percentage swelling ratio of AAm/SA hydrogels was increased up to 2946–12,533%, while AAm hydrogels swelled up to 1326–1618%. The values of equilibrium water content of the hydrogels are between 0.9297–0.9921. Diffusion behavior was investigated. Water diffusion into hydrogels was found to be non‐Fickian in character. Adsorption properties of AAm/SA hydrogels in aqueous thionin solution have been investigated. Finally, the amount of sorbed thionin per gram of dry hydrogel (q_e) was calculated to be 4.81 × 10^?6?11.69 × 10^?6 mol thionin per gram for hydrogels. Removal efficiency (RE%) of the AAm/SA hydrogels was changed range 37.03–68.82%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 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     

Swelling and Diffusion Properties of Poly(acrylamide-co-maleic acid) Hydrogels: A Study with Different Crosslinking Agents

Crosslinked hydrogels comprising acrylamide (AAm) and maleic acid (MA) were synthesized by free radical polymerization in presence of a crosslinker using ammonium persulfate (APS) and N,N,N¹,N¹-tetramethylethylenediamine (TMEDA) as initiator and activator, respectively. The crosslinked hydrogel formation was confirmed by IR analysis. The swelling/de-swelling characteristics were studied in detail for crosslinked poly(acrylamide-co-maleic acid) [poly(AAM-co-MA)] hydrogels containing different amounts of maleic acid. Four different crosslinkers such as 1,2-ethyleneglycol dimethacrylate (EGDMA), 1,4-butanediol diacrylate (BDDA), 1,6-hexanediol diacrylate (HDDA), and diallyl phthalate (DP) were utilized to study their influence on the swelling behavior of the hydrogels. The effect of reaction parameters such as the concentration of crosslinker and initiator on swelling capacity of the crosslinked poly(AAm-co-MA) hydrogels was also investigated. Further, the influence of various salts, simulated biological fluids, and pH solutions on the swelling pattern of hydrogels was studied extensively. Phase separation morphology of crosslinked hydrogels was also studied by differential scanning calorimetry. The morphology of crosslinked hydrogels were revealed using scanning electron microscopy (SEM).     

Undesirable effects of heating on hydrogels

Heating is the most conventional drying method for removing water from as‐synthesized hydrogels in laboratory and industry. In this article, the effects of the heating temperature (60–200°C) and time (10 min–24 h) on swelling properties of highly absorbent hydrogels based on 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS), acrylic acid (AA), potassium acrylate (KA), and acrylamide (AM) were studied. Crosslinkers methylene bisacrylamide (MBA) and poly(ethyleneglycol) dimethacrylate (PEGDMA) were used in the syntheses. Depending on the hydrogel structural composition and its drying temperature and time, the swelling capacities were extremely changed. Generally, AA‐, KA‐, and AM‐based hydrogels showed more hydrolytic‐thermal stability than the corresponding AMPS‐based hydrogels. MBA‐crosslinked hydrogels generally exhibited higher vulnerability against heating. Swelling of PEGDMA‐crosslinked poly(AM‐KA‐AA) hydrogel was greatly increased after heating, whereas its analogousAM‐free sample exhibited huge loss of swelling. PEGDMA‐crosslinked poly(AMPS) samples also exhibited swelling reduction after drying. Rheological studies showed that the storage modulus was highly reduced (～ 5200 Pa) after heating of MBA‐crosslinked poly(AMPS) hydrogels, which reconfirmed the crosslink cleavage. Mechanistic discussions were proposed for the thermal‐induced swelling changes. It was concluded that the chemical nature of both crosslinker and monomer must be taken into consideration to choose the temperature and time of the hydrogel drying. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Relationship between the swelling process and the releases of water soluble agrochemicals from radiation crosslinked acrylamide/itaconic acid copolymers

Summary An attempt was made in this study to relate the releases of water soluble herbicide (sodium 2,2 dichloropropionate (Dowpon)) and model fertilizers (ammonium nitrate, potassium nitrate and ammonium sulfate) from the cylindrical devices of radiation crosslinked poly(acrylamide/itaconic acid) (AAm/IA) copolymers with the swelling that may effect the release behaviour. AAm/IA copolymers containing agrochemicals are prepared by two different composition of itaconic acid and two different γ-rays doses. The agrochemicals were trapped in the gels by including it in the feed mixture of radiation polymerization. The equilibrium swelling, diffusional exponent, and diffusion and intrinsic diffusion coefficients of the process were obtained. The agrochemical dissolution was determined by conductimetric method. The maximum concentrations of releasing agrochemicals and initial releasing rates were calculated by using of second order kinetics equation. The agrochemical releases appeared to be controlled by swelling. As a result, if AAm/IA hydrogels containing agrochemicals were swelled in water, release of agrochemicals was decreased with the raising of γ-rays doses and itaconic acid quantities in the hydrogel. Received: 26 April 2000/Revised version: 2 August 2000/Accepted: 4 September 2000