A poly(γ‐glutamic acid)‐based hydrogel loaded with superoxide dismutase for wound healing

The purpose of this study was to develop a poly(γ‐glutamic acid) (γ‐PGA)‐based hydrogel loaded with superoxide dismutase (SOD) to accelerate wound healing. First, γ‐PGA was modified with taurine (γ‐PGAS), and then the SOD‐loaded γ‐PGAS/γ‐PGA hydrogel (SOD‐PGAS/PGA‐H) was prepared by cross‐linking of ethylene glycol diglycidyl ether. The swelling behavior and water vapor transmission rate revealed that PGAS/PGA‐H could create a moist environment for wound surface. In vitro kinetics of SOD release showed that SOD released from PGAS/PGA‐H maintained high activity and SOD‐PGAS/PGA‐H effectively scavenged the superoxide anion. The results of our fibroblast proliferation experiments showed that PGAS/PGA‐H had good cytocompatibility. The effects of SOD‐PGAS/PGA‐H on wound healing were examined in a Type I diabetic rat model with full‐thickness wounds. Twenty‐one days after grafted to wounds, SOD‐PGAS/PGA‐H exhibited a higher rate of wound healing than control group and showed increased collagen deposition and epithelialization. SOD‐PGAS/PGA‐H seems to promote better wound healing and thus might be a promising candidate for wound healing management. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42033.     

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     

Synthesis and properties of a superabsorbent from an ultraviolet‐irradiated waste nameko mushroom substrate and poly(acrylic acid)

To better use the waste nameko mushroom substrate (WNMS) and prevent its pollution into the environment, a novel superabsorbent polymer was synthesized via the UV irradiation copolymerization of acrylic acid and WNMS in the presence of an initiator (dimethoxy‐2‐phenylacetophenone and ammonium persulfate) and crosslinker N,N′‐methylenebisacrylamide. The factors that had an influence on the water absorbency of the superabsorbent polymer were investigated and optimized. Under the optimized conditions, WNMS–poly(acrylic acid) was obtained. Its swelling behaviors, which followed the pseudo‐second‐order swelling kinetic model, were investigated in distilled water (1701 g/g) and a 0.9 wt % NaCl solution (388 g/g). The water absorbency was 1011 g/g in a 0.1 wt % urea solution and 80% amount of urea diffused into the gels. The urea diffusion followed a Fickian diffusion mechanism. Moreover, the product showed excellent water retention capabilities under the condition of high temperature or high pressure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40471.     

Photo/pH dual‐responsive biocompatible poly(methacrylic acid)‐based particles for triggered drug delivery

A novel dual‐responsive (light and pH) particle based on poly(methacrylic acid), poly(methacrylic acid)–poly[1‐(2‐nitrophenyl)ethane‐1,2‐diyl bis(2‐methylacrylate)]was prepared with the facile method of two‐step homogeneous radical polymerization with methacrylic acid as the monomer and 1‐(2‐nitrophenyl)ethane‐1,2‐diyl bis(2‐methylacrylate) as a photodegradable crosslinker. Photolytic assessments were conducted upon irradiation with a UV lamp; this led to particle disintegration caused by cleavage of the photolabile crosslinking points. The light‐dependent degradation was investigated through particle size changes, absorption spectra variations, surface morphology changes, Fourier transform infrared spectroscopy, and the release of Nile red from the particles after irradiation. The pH dependence of the particle systems induced by the protonation and deprotonation of poly(methacrylic acid) was also confirmed by fluorescence spectroscopy. The triggered release of fluorescein diacetate was investigated to demonstrate that the release behavior in cells was light dependent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44003.     

Oxygen plasma modification of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) film surfaces for tissue engineering purposes

Plasma glow‐discharge application is known as a technique to coat or modify the surfaces of various materials. In this study, the influence of oxygen rf‐plasma treatment on surface and bulk properties of a biological polyester, poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), were studied by determining water content and water contact angle, and by using X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The plasma‐treated films absorbed more water than the untreated film, and the absorbance increased with the total power applied. The water contact angles decreased and O/C atomic ratio increased on treatment, indicating that the material became more hydrophilic due to increases in the oxygen‐containing functional groups on the surface of the polymer. A direct relation could be observed when the O/C ratio was plotted against the total power applied (treatment duration × treatment power). SEM revealed a visual record of surface modification, the extent of which increased with increased total power. It was thus possible to alter the surface chemistry and relevant properties of the polymer film using oxygen plasma as a tool. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1285–1289, 2003     

Poly(ethylene glycol)‐containing cationic hydrogels with lipophilic character

Not much effort has been focused towards the development of hydrogels that swell in nonpolar solvents. We have synthesized a new set of polyelectrolyte hydrogels and demonstrated their ability to absorb a less‐polar or nonpolar organic solvent, as well as their ability to resist gel‐collapse in a predominantly nonpolar medium. The hydrogels were prepared by free radical polymerization of different molar ratios of poly(ethylene glycol) methyl ether acrylate and (3‐(methacryloylamino)propyl)‐trimethyl ammonium chloride as comonomers in an aqueous medium. Their swelling behavior in organic solvents was studied by varying the dielectric constant of the swelling medium including mixed‐solvent systems. Besides a high degree of swelling (up to 200 times) in polar solvents, some of the hydrogels also exhibited moderate swelling (up to 15 times) in less‐polar organic solvents. Hydrogels samples with high cationic content showed drastic change in swelling extent in some of the mixed‐solvent systems. It was also interesting to note that the retention of significant swelling in dimethyl sulphoxide–toluene mixture with even 90% toluene content for some compositions. These polyelectrolyte hydrogels with improved lipophilicity opens up greater opportunities for the development of even superior soft materials through proper structural optimizations that would successfully function for a wider range of solvents. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39873.     

Improved swelling–deswelling behavior of poly(N‐isopropyl acrylamide) gels with poly(N,N′‐dimethyl aminoethyl methacrylate) grafts

Thermoresponsive and pH‐responsive gels were synthesized from N‐isopropyl acrylamide (NIPA) and N,N′‐dimethyl aminoethyl methacrylate (DMAEMA) monomers. Gelation reactions were carried out with both conventional free‐radical polymerization (CFRP) and controlled free‐radical polymerization [reversible addition fragmentation transfer (RAFT)] techniques. The CFRP gels were prepared by polymerizing mixtures of NIPA and DMAEMA in 1,4‐dioxane in presence of N,N'‐methylene bisacrylamide (BIS) as cross‐linker. The RAFT gels were prepared by a the polymerization of NIPA via a similar process in the presence of different amounts of poly(N,N′‐dimethyl aminoethyl methacrylate) macro chain‐transfer agent and the crosslinker. These gels were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry. SEM analysis revealed a macroporous network structure for the RAFT gels, whereas their volume phase‐transition temperatures (VPTTs) were found to be in the range 32–34°C, close to that of poly(N‐isopropyl acrylamide) gels. However, the CFRP copolymer gels exhibited a higher VPTT; this increased with increasing DMAEMA content. The RAFT gels exhibited higher swelling capabilities than the corresponding CFRP gels and also showed faster shrinking–reswelling behavior in response to changes in temperature. All of the gels showed interesting pH‐responsive behavior as well. The unique structural attributes exhibited by the RAFT gels can potentially open up opportunities for developing new materials for various applications, for example, as adsorbents or carrier of drugs or biomolecules. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42749.     

Some Mechanical Properties of Poly[(acrylic acid)‐co‐(itaconic acid)] Hydrogels

Two series of hydrogels of poly[(acrylic acid)‐co‐(itaconic acid)] have been prepared by copolymerization in solution using tetrafunctional N,N′‐methylenebisacrylamide (NMBA) as cross‐linker. The resulting polymer was swollen in water at 298 K to yield homogenous transparent hydrogels. These hydrogels were characterized in terms of swelling and compression‐strain measurements. The influence of the comonomer composition and concentration of cross‐linking agent on volumetric swelling and the mechanical properties of these hydrogels were investigated. Inefficient cross‐linking is indicated by the small values of ν_e relative to the theoretical cross‐linking densities.

Dependence of measured affective cross‐linking density (ν_e) on the theoretical cross‐linking density (ν_t) for acrylic acid/itaconic acid hydrogels prepared at a fixed composition of AA80/AI20 wt.‐%, but at different concentrations of NMBA.     

Synthesis and characterization of novel pH‐responsive poly(2‐hydroxylethyl methacrylate‐co‐N‐allylsuccinamic acid) hydrogels for drug delivery

In this study, N‐allylsuccinamic acid (NASA) was synthesized in a single step with a yield of 85%. Carboxylic acid containing NASA was characterized through Fourier transform infrared (FTIR) radiation and ¹H‐NMR and ¹³C‐NMR analysis, and then it was used for synthesis of poly(2‐hydroxylethyl methacrylate‐co‐N‐allylsuccinamic acid) [p(HEMA‐co‐NASA)] hydrogels. The structure of the obtained pH‐responsive p(HEMA‐co‐NASA) hydrogels were characterized with FTIR spectroscopy and scanning electron microscopy analysis, and their swelling characterization was carried out under different drug‐release conditions. In the application step of the study, the hydrogels were used for the in vitro release of vitamin B12 and Rhodamine 6G, which were selected as model drugs. We determined that the hydrogels used as a drug‐delivery matrix could release the drug they had absorbed under different release conditions (phosphate‐buffered saline, 0.9% NaCl, and pH 1.2) at high rates for time periods of up to 24 h. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39660.     

Preparation and characterization of thermo‐sensitive poly(vinyl alcohol)‐based hydrogel as drug carrier

Poly(vinyl alcohol)s (PVA) with high and low molecular weights were chemically modified by introducing acetaldehyde onto the polymer backbone to induce thermal‐responsive properties. The influence of both molecular weight ( ) and acetalization degree on the lower critical solution temperature (LCST) of thermo‐sensitive polymer was investigated. Moreover, a temperature responsive hydrogel was prepared by controlled cross‐linking of acetalized poly(vinyl alcohol) (APVA) and glutaraldehyde. As a model drug, ciprofloxacin was introduced into the prepared thermal sensitive hydrogel to reveal the drug loading and release behaviors. The structure, thermo‐sensitivity, swelling/deswelling kinetics, morphology, and drug loading/release behaviors were also investigated. The results indicated that the APVA polymer solution exhibited temperature responsivity, and APVA with high acetalization degree showed low LCST, whereas those with high PVAs showed high LCST. Meanwhile, morphology study was identical with the swelling/de‐swelling behavior. The loading and release of ciprofloxacin were controllable. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39720.     

p(AAm/TA)‐based IPN hydrogel films with antimicrobial and antioxidant properties for biomedical applications

Interpenetrating polymer networks (IPN), either semi‐IPN (s‐IPN) or full IPN, based on a natural polymer tannic acid (TA) and synthetic poly(acrylamide) (p(AAm)) were prepared by incorporation of TA during p(AAm) hydrogel film preparation with and without crosslinking of TA simultaneously. The synthesis of p(AAm/TA) s‐IPN and IPN hydrogels with different amounts of TA were prepared by concurrent use of redox polymerization and epoxy crosslinking. The p(AAm)‐based hydrogels were completely degraded at 37.5°C within 9 and 2 days at pHs 7.4 and 9, respectively. Biocompatibility of p(AAm), s‐IPN, and IPN were tested with WST assay and double staining, they had 75% cell viability up to almost 20 μg mL^?1 concentration against L929 fibroblast cell. Antioxidant properties of IPN and s‐IPN hydrogels were investigated with FC and ABTS^? methods. Antimicrobial properties of TA‐containing s‐IPN, and IPN hydrogels were determined against three common bacterial strains, Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538, and Bacillus subtilis ATCC 6633, and it was found that p(AAm/TA)‐based s‐IPN and IPN hydrogels are effective antimicrobial and antioxidant materials. Moreover, almost up to day‐long linear TA release profiles were obtained from IPN and s‐IPN hydrogels in phosphate buffer solution at pH 7.4 at 37.5°C. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41876.     

Silicone hydrogels based on a novel amphiphilic poly(2‐methyl‐2‐oxazoline)‐b‐poly(dimethyl siloxane) copolymer

A novel amphiphilic hydrogel based on poly(2‐methyl‐2‐oxazoline)‐b‐poly(dimethyl siloxane) (PMeOx–PDMS) block copolymer was developed. First of all, PMeOx–PDMS macromonomer was synthesized by coupling mono‐hydroxylated PMeOx with PDMS followed by end‐capping with methacrylate group. The structures of each step were characterized by NMR and titration. After that, silicone hydrogels were prepared by UV‐initiated copolymerization of PMeOx–PDMS macromonomer with monomers such as 2‐hydroxyethyl methacrylate in the presence of a crosslinker. Measurements of the hydrogels' water contact angle, equilibrium water content, and tensile properties showed that the hydrogels possessed better hydrophilic surface, higher water content, and better ion permeability with the increase of the content of the macromonomer PMeOx–PDMS. Meanwhile, the tensile strength and Young's modulus of the hydrogels decreased slightly. Protein adsorption tests showed that the hydrogels had strong antifouling ability after the incorporation of PMeOx. This newly described hydrogel demonstrated attractive properties to serve as ophthalmic biomaterial. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39867.     

Isothermal kinetics of (E)‐4‐(4‐metoxyphenyl)‐4‐oxo‐2‐butenoic acid release from a poly(acrylic acid‐co‐methacrylic acid) hydrogel

A kinetic study of the release of the drug (E)‐4‐(4‐metoxyphenyl)‐4‐oxo‐2‐butenoic acid (MEPBA) from a poly(acrylic acid‐co‐methacrylic acid) (PAA‐co‐MA) hydrogel was performed. The isothermal kinetic curves of MEPBA release from the PAA‐co‐MA hydrogel in bidistilled water at different temperatures ranging from 20 to 40°C were determined. The reaction rate constants of the investigated process were determined with the initial rate, the saturation rate, and Peppas's semiempirical equation. Also, a model‐fitting method for the determination of the kinetics model of drug release was applied. The influence of α at the values of the kinetic parameters and the presence of a compensation effect was established. A procedure for the determination of the distribution function of the activation energies was developed. This procedure was based on the experimentally determined relationship between the activation energy and α. The mechanism of active compound release is discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Rapid swelling and deswelling of semi‐interpenetrating network poly(acrylic acid)/poly(aspartic acid) hydrogels prepared by freezing polymerization

Hydrogels with semi‐interpenetrating networks composed of poly(acrylic acid) (PAAc) and poly(aspartic acid) (PASP) have great potential for pharmaceutical and biomedical applications. In this study, we aimed to synthesize semi‐interpenetrating PAAc/PASP hydrogels with improved swelling–deswelling properties via two‐step polymerization, in which the first step of polymerization was performed at 37 °C for 15 min and the second step, the freezing polymerization, was performed at ?20 °C for 24 h. The synthesized hydrogels were characterized with field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The swelling and deswelling behaviors of the hydrogels in response to the ionic strength of the buffer solution were investigated. The Schott's swelling kinetic model was used to elucidate the swelling behavior of the hydrogels. The swelling and deswelling rates of the hydrogels prepared via freezing polymerization were faster than those of the hydrogels prepared via conventional polymerization. This was attributed to the large mean pore size of the freeze‐polymerized hydrogels. The PAAc/PASP hydrogels that underwent freezing polymerization had better swelling–deswelling characteristics than the PAAc hydrogels. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43515.     

Controlled delivery of growth‐hormone‐releasing peptide 6 from the poly(lactic‐co‐glycolic acid)–poly(ethylene glycol)–poly(lactic‐co‐glycolic acid) copolymer and the effect of a growth‐hormone‐releasing peptide 6–copolymer hydrogel on the growth of rex rabbits

Growth‐hormone‐releasing peptide 6 (GHRP‐6) plays an important role in animal growth. However, there have been few studies focusing on the effect of GHRP‐6 on animal growth through controlled release systems. We synthesized the poly(lactic‐co‐glycolic acid) (PLGA)–poly(ethylene glycol) (PEG)–PLGA copolymer to investigate its controlled released effect on GHRP‐6 in vitro and to study the effect of a GHRP‐6–copolymer hydrogel on the growth of rex rabbits. The copolymer was synthesized with ring‐opening copolymerization and characterized by ¹H‐NMR. The interaction between GHRP‐6 and the copolymer was characterized by Fourier transform infrared spectroscopy and X‐ray diffraction. The body weight, serum level of insulin‐like growth factor 1 (IGF‐1), and hair coat quality were studied in rex rabbits. The results show that hydrogen bonds formed between the N? H group in GHRP‐6 and the C?O group in the copolymer. The release mechanism of GHRP‐6 was a combination of a diffusion‐controlled mechanism and an erosion‐controlled mechanism in the copolymer. The serum level of IGF‐1, hair coat quality, and body weight were all significantly higher in the GHRP‐6–copolymer hydrogel group than in the other groups. These results indicate that the copolymer effectively controlled the release of GHRP‐6. In addition, the GHRP‐6–copolymer hydrogel increased the synthesis of IGF‐1 for a prolonged period and, thereby, increased the rex rabbits' growth and hair coat quality. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40185.     

Encapsulation and delivery of protein from within poly(sulfobetaine) hydrogel beads

Advancement of therapeutic protein therapies can be hindered by their poor stability and short in vivo half-life. There is emerging evidence that biocompatible zwitterionic materials can prevent nonspecific interactions within proteins systems that contribute to protein instability. Here, zwitterionic hydrogel beads are synthesized from poly(sulfobetaine methyl methacrylate), pSB, using an inverse emulsion, free radical polymerization reaction technique. The transport properties within the zwitterionic hydrogels were characterized using ¹H NMR diffusometry. Equilibrium water content as high as 0.90 was measured for the synthesized hydrogels. Our study revealed that the pSB hydrogels are nontoxic, ion responsive, and their swelling is temperature dependent. The zwitterionic hydrogel beads were capable of undergoing lyophilization without aggregation. Hydrogel beads were loaded with a model protein, bovine serum albumin (BSA), using a postfabrication loading technique. The protein loading was studied using confocal laser microscopy, indicating homogenous protein dispersion of up to 40 μg BSA/mg hydrogel within the beads. Furthermore, the release rate of the protein from the synthesized hydrogel was studied at different crosslinker to monomer ratios. The protein encapsulated within the zwitterionic hydrogel had slower rates of thermal aggregation compared to nonencapsulated protein in solution. Furthermore, the protein-loaded inside the zwitterionic hydrogel better maintained its bioactivity.     

Preparation and drug‐release behavior of minocycline‐loaded poly[hydroxyethyl methacrylate‐co‐poly(ethylene glycol)–methacrylate] films

In this work, biocompatible hydrogel matrices for wound‐dressing materials and controlled drug‐release systems were prepared from poly[hydroxyethyl methacrylate‐co‐poly(ethylene glycol)–methacrylate] [p(HEMA‐co‐PEG–MA] films via UV‐initiated photopolymerization. The characterization of the hydrogels was conducted with swelling experiments, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis (differential scanning calorimetry), and contact‐angle studies. The water absorbency of the hydrogel films significantly changed with the change of the medium pH from 4.0 to 7.4. The thermal stability of the copolymer was lowered by an increase in the ratio of poly(ethylene glycol) (PEG) to methacrylate (MA) in the film structure. Contact‐angle measurements on the surface of the p(HEMA‐co‐PEG–MA) films demonstrated that the copolymer gave rise to a significant hydrophilic surface in comparison with the homopolymer of 2‐hydroxyethyl methacrylate (HEMA). The blood protein adsorption was significantly reduced on the surface of the copolymer hydrogels in comparison with the control homopolymer of HEMA. Model antibiotic (i.e., minocycline) release experiments were performed in physiological buffer saline solutions with a continuous flow release system. The amount of minocycline release was shown to be dependent on the HEMA/PEG–MA ratio. The hydrogels have good antifouling properties and therefore are suitable candidates for wound dressing and other tissue engineering applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of cassava starch graft poly(acrylic acid) and poly[(acrylic acid)‐co‐acrylamide] and polymer flocculants for wastewater treatment

Starch‐g‐poly(acrylic acid) and poly[(acrylic acid)‐co‐acrylamide] synthesized via chemically crosslinking polymerization were then each mixed with inorganic coagulants of aluminum sulfate hydrate [Al₂(SO₄)₃·18H₂O], calcium hydroxide [Ca(OH)₂], and ferric sulfate [Fe₂(SO₄)₃] in a proper ratio to form complex polymeric flocculants (CPFs). All CPFs exhibited low water absorbency than those of the uncomplexed superabsorbent copolymers. The color reduction by the CPFs was tested with both synthetic wastewater and selected wastewater samples from textile industries. The synthetic wastewater was prepared from a direct dye in a concentration of 50 mg dm^?3 at pH 7. The CPFs of poly[(acrylic acid)‐co‐acrylamide] with calcium hydroxide at a ratio of 1:2 is the most effective CPF for the wastewater color reduction. The CPF concentration of 500 mg dm^?3 could reduce the color of the synthetic wastewater containing the direct dye solution by 95.4% and that of the industrial wastewater by 76%. Starch‐g‐poly(acrylic acid)/Ca(OH)₂ CPF can reduce the synthetic direct dye and the industrial wastewater by 74% and 18%, respectively. Chemical oxygen demand, residual metal ion concentrations, pHs, turbidity of the wastewater were also investigated and the potential use of the complex polymer flocculants for textile wastewater treatment was indicated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2915–2928, 2006     

Synthesis,characterization and polychelatogenic properties of poly[(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid)‐co‐(methacrylic acid)]

Poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid), poly(methacrylic acid), and five copolymers of poly[(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐co‐(methacrylic acid)] were synthesized by radical polymerization and obtained in yields >97%. The polymers were characterized by FT‐IR, [¹H]NMR, and [¹³C]NMR and studied by means of the Liquid‐phase Polymer‐based Retention (LPR) technique. The metal ion retention ability of the copolymers for Cu(II), Cd(II), Co(II), Hg(II), Ni(II), Zn(II), Cr(III) and Ag(I) was investigated at different pH values because of their environmental and analytical interest. The retention profiles of the copolymers were compared with those of the corresponding homopolymers and retention of metal ions was found to increase with increasing pH. © 2001 Society of Chemical Industry     

Hybrid double‐network hydrogel based on poly(aspartic acid) and poly(acryl amide) with improved mechanical properties

Hydrogels usually have a smaller mechanical strength and toughness than generic polymeric materials. Therefore, many studies report improvements for mechanical properties of hydrogels by preparing double‐network hydrogels, nanocomposite hydrogels, and nanostructured hydrogels. In this study, interpenetrating‐type dually‐crosslinked hydrogels were prepared via free radical crosslinking polymerization of acrylamide monomers in the presence of poly(aspartic acid) and subsequent immersion in a metal ion containing aqueous solution to induce extra physical crosslinking through ionic or coordination bonding. Using this approach, the mechanical properties of inherently weak and brittle homopolymer gels could be improved via interpenetrating the double network formed by both covalent bonding and metal coordination‐assisted reversible physical crosslinks. The preparation, swelling behavior, morphology, and mechanical properties of these hydrogels are presented. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45925.