Cross-linked Acrylamide Research Articles

Crosslinking acrylamide with EDTA-intercalated layered double hydroxide for enhanced recovery of Cr(VI) and Congo red: Adsorptive and mechanistic study

We prepared ethylenediaminetetraacetic acid (EDTA)-intercalated MgAl-layered double hydroxide (LDH-EDTA), then grafted acrylamide (AM) to the LDH-EDTA by a cross-linking method to yield a LDH-EDTA-AM composite; we then evaluated its adsorptive ability for Congo red (CR) and hexavalent chromium (Cr(VI)) in single and binary adsorption systems. The adsorption process on LDH-EDTA-AM for CR and Cr(VI) achieved equilibrium quickly, and the removal efficiencies were minimally affected by initial pH. The maximum uptake quantities of CR and Cr(VI) on LDH-EDTA-AM were 632.9 and 48.47 mg/g, respectively. In mixed systems, chromate removal was stimulated by the presence of CR, while the adsorption efficiency of CR was almost not influenced by coexisting Cr (VI). The mechanisms involved electrostatic attraction, surface complexation, and anion exchange for the adsorption of both hazardous pollutants. In the Cr(VI) adsorption process, reduction also took place. The removal efficiencies in real contaminated water were all higher than those in the laboratory solutions.

Semi-interpenetrating nanosilver doped polysaccharide hydrogel scaffolds for cutaneous wound healing

The extensive advancement with novel wound dressing materials functionalized with desirable properties, often touted as a panacea for cuts and burns afflicting various pathologies. However, it would indeed be a hard task to isolate any such material which perfectly fits the needs of any biomedical issue at hand. Biocompatibility, biodegradability as well as non-toxicity of natural polysaccharide served as a versatile and tunable platform for designing natural polysaccharide based scaffolds as an attractive tool in tissue engineering with a greater degree of acceptability. In this regard, we aimed to fabricate a semi interpenetrating hydrogel via exploiting the nontoxic and immune-stimulatory nature of galacto-xyloglucan (PST001) which was further doped with silver nanoparticles to formulate SNP@PST. The wound healing potential of SNP@PST was then studied both with in vitro and preclinical mice models. The current study gives a formulation for cost effective preparation of polysaccharide hydrogels using acrylamide crosslinking with improved biocompatibility and degradability. Wound healing studies in mice proved the efficiency of gels for the clinical application wherein the incorporation of nanosilver greatly enhanced the antimicrobial activity.

Complementary-DNA-Strand Cross-Linked Polyacrylamide Hydrogels

We examine networks of complementary-DNA-strand cross-linked polyacrylamide, with and without covalent N,N′-methylene(bis)acrylamide cross-linking, using rheological time–temperature superposition ...

Nanocomposite interpenetrating hydrogels with high toughness and good self-recovery

It is particularly desirable to fabricate highly tough hydrogels with excellent self-recoverable properties for applications where high stress is required. In this work, we prepared a tough, fast self-recoverable nanocomposite hydrogel by chemical cross-linking of acrylamide (AM) monomers with vinyl-modified silica nanoparticles (VSNPs), combined with physical cross-linking of polyvinyl alcohol (PVA). The uniaxial tensile test showed that the nanocomposite hydrogel has excellent mechanical properties. The maximum elongation at break was as high as 666%, and the tensile strength was as high as 1.68 MPa. Cyclic loading-unloading tests revealed the excellent self-healing properties of the nanocomposite hydrogel. It is worth noting that the nanocomposite hydrogel exhibited higher strength after two loading-unloading cycles, due to the orientation of the PVA when stretched. In addition, the effects of PVA, VSNPs, and AM concentrations, and the number of PVA freeze-thaw cycles and freezing duration on the mechanical properties of the hydrogels were investigated in detail.

Conformal Hydrogel Coatings on Catheters To Reduce Biofouling.

Reducing biofouling while increasing lubricity of inserted medical catheters is highly desirable to improve their comfort, safety, and long-term use. We report here a simple method to create thin (∼30 μm) conformal lubricating hydrogel coatings on catheters. The key to this method is a three-step process including shape-forming, gradient cross-linking, and swell-peeling (we label this method as SGS). First, we took advantage of the fast gelation of agar to form a hydrogel layer conformal to catheters; then, we performed a surface-bound UV cross-linking of acrylamide mixed in agar in open air, purposely allowing gradual oxygen inhibition of free radicals to generate a gradient of cross-linking density across the hydrogel layer; and finally, we caused the hydrogel to swell to let the non-cross-linked/loosely attached hydrogel fall off, leaving behind a surface-bound, thin, and mostly uniform hydrogel coating. This method also allowed easy incorporation of different polymerizable monomers to obtain multifunctionality. For example, incorporating an antifouling, zwitterionic moiety sulfobetaine in the hydrogel reduced both in vitro protein adsorption and in vivo foreign-body response in mice. The addition of a biocidal N-halamine monomer to the hydrogel coating deactivated both Staphylococcus aureus ( S. aureus) and Escherichia coli ( E. coli) O157:H7 within 30 min of contact and reduced biofilm formation by 90% compared to those of uncoated commercial catheters when challenged with S. aureus for 3 days. The lubricating, antibiofouling hydrogel coating may bring clinical benefits in the use of urinary and venous catheters as well as other types of medical devices.

Influence of Chain Structures of Starch on Water Absorption and Copper Binding of Starch‐Graft‐Itaconic Acid Hydrogels

Bio‐based hydrogels destined for use as low cost renewable biosorbents are synthesized. The impact of the two components of starch, amylose, and amylopectin, on the properties of the hydrogels is assessed. Hydrogels are synthesized by solution based graft copolymerization of itaconic acid monomers on a corn starch backbone in the presence of an acrylamide crosslinker and the potassium persulfate/sodium bisulfite redox initiator pair. Three types of corn starch are used: normal corn starch, waxy starch, and high amylose starch. The amylose:amylopectin ratios are: 27:73 for normal starch (NS), 70:30 for high amylose starch (HAS), and 0:100 for waxy starch (WS). Swelling tests performed in a variety of solutions show no significant differences in swelling capacity among the hydrogels. The hydrogels also perform similarly in copper adsorption tests. Overall, these results indicate that native corn starch is as effective as amylopectin and amylose‐rich starch.

Hydrogel nanocomposites based on chitosan-g-polyacrylamide and silver nanoparticles synthesized using Curcuma longa for antibacterial applications

Hydrogel nanocomposites based on chitosan-g-polyacrylamide and silver nanoparticles (Cs-g-PAAm/AgNPs) were developed by simple, cost effective, and eco-friendly process at room temperature. First, the hydrogels were prepared via grafting copolymerization and crosslinking of acrylamide (AAm) onto chitosan (Cs) with various weight ratios, using potassium persulfate as initiator and N,N′-methylenebisacrylamide as crosslinker, and then hydrolyzed to achieve materials with uppermost swelling properties. Finally, the AgNPs were biosynthesized and entrapped into hydrogels as templates using aqueous silver nitrate as precursor and Curcuma longa tuber extract as both reducing and stabilizing agents. The influences of the templates and the silver precursor concentrations on the AgNP formation and the properties of the elaborated nanocomposites were investigated. The UV–visible spectroscopy has confirmed the occurrence of the nanosilver particle formation, while the X-ray diffraction analysis has evidenced their face-centered cubic crystalline phase. The inductively coupled plasma analysis has revealed that the extent of AgNPs into the network increases by a decrease in Cs weight ratios and an increase in AgNO3 concentrations. Transmission electron microscope images have showed a spherical shape of AgNPs with average sizes <26 nm. Interactions between hydrogel functional groups and those of proteins extracted from C. longa, which are probably the capping ligands of the AgNPs, were suggested from Fourier transform-infrared spectroscopy. Slight enhance in thermal stability of nanocomposites was noticed from thermogravimetric analysis. Besides, the swelling and retention capacities were affected by both Cs and AgNP contents. Furthermore, the swelling kinetics was found to obey the second-order model with non-Fickian diffusion. The antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria was examined by both zone inhibition and dynamic shake flask methods and the results have showed an efficient activity of AgNP-loaded hydrogels with a maximum of killing ratio of 99.99%. Finally, it is suggested that the optimized hydrogel nanomaterials can be candidates for bio-applications.

Successful Coupling of a Bis-Amidoxime Uranophile with a Hydrophilic Backbone for Selective Uranium Sequestration.

The amidoxime group (-RNH2NOH) has long been used to extract uranium from seawater on account of its high affinity toward uranium. The development of tunable sorbent materials for uranium sequestration remains a research priority as well as a significant challenge. Herein, we report the design, synthesis, and uranium sorption properties of bis-amidoxime-functionalized polymeric materials (BAP 1-3). Bifunctional amidoxime monomers were copolymerized with an acrylamide cross-linker to obtain bis-amidoxime incorporation as high as 2 mmol g-1 after five synthetic steps. The resulting sorbents were able to uptake nearly 600 mg of uranium per gram of polymer after 37 days of contact with a seawater simulant containing 8 ppm uranium. Moreover, the polymeric materials exhibited low vanadium uptake with a maximum capacity of 128 mg of vanadium per gram of polymer. This computationally predicted and experimentally realized selectivity of uranium over vanadium, nearly 5 to 1 w/w, is one of the highest reported to date and represents an advancement in the rational design of sorbent materials with high uptake capacity and selectivity.

Synthesis and characterization of zein-based cryogels and their potential as diesel fuel absorbent

In this study, zein-protein based cryogels were synthesized by solution-based graft copolymerization of acrylic acid monomers onto zein protein backbones in the presence of an acrylamide crosslinker and initiators (sodium bisulfite and potassium persulfate). The grafting was confirmed by Fourier transform infrared spectroscopy. The thermal properties of the cryogels were assessed by thermogravimetric analysis and their morphology was studied by scanning electron microscopy and Brunauer–Emmett–Teller surface analysis. It was found that freezing the materials using liquid nitrogen at −196°C before drying increased the surface area of the cryogels as compared to freezing at −20°C. Dynamic mechanical analysis tests revealed that cryogels with increased acrylic acid content captured ambient moisture more quickly. The absorption capacity tests were performed in water and in diesel fuel. The highest equilibrium swelling of cryogels in distilled water reached 119.5g/g of cryogel after 1h while the highest equilibrium swelling in diesel fuel reached 49.8g/g of cryogel in 15min.

Synthesis and characterization of zein-based superabsorbent hydrogels and their potential as heavy metal ion chelators

Superabsorbent hydrogels were synthesized by solution-based graft copolymerization of acrylic acid monomers on the hydrolyzed zein protein backbones in the presence of an acrylamide crosslinker, sodium bisulfite and potassium persulfate as initiators. The grafting was confirmed by Fourier transform infrared spectroscopy and the morphology was studied by scanning electron microscopy. A loose structure was observed in the hydrolyzed zein protein-g-polyacrylic acid. Moreover, differential scanning calorimetry and swelling tests were performed to evaluate the effect of the formulations on the thermal and swelling properties of the hydrogels. The highest equilibrium swelling value in distilled water reached 239.6 g/g of hydrogel. The potential of these materials as heavy metal ions chelator was also assessed. The preliminary results showed that the hydrogels had a good copper ion chelation capacity (maximum of 208 mg/g at pH 4.5), probably due to the presence of a large number of functional groups from the polyacrylic acid and the hydrolyzed zein protein.

Roles of chemical and physical crosslinking on the rheological properties of silica-doped polyacrylamide hydrogels

This paper examines the nanoparticle (NP) influence on energy storage and dissipation in hydrogel nanocomposites (HNCs). To obtain fundamental insights into mechanical enhancement, a model system involving the in situ free-radical polymerization of acrylamide with bis-acrylamide (bis) and silica NPs is adopted. The loss tangents of the unmodified polymer networks span three orders of magnitude, and the weak attraction between silica and poly(acrylamide) (PA)—as compared to composites with a stronger NP-polymer interaction—makes these HNCs particularly sensitive to systematic variations in (i) NP size and concentration and (ii) monomer and crosslinker concentrations. From the dynamic shear moduli during polymerization, and their spectra at steady-state, silica NPs in PA behave as multi-functional, physical crosslinking centers that increase the storage modulus, particularly in very weakly bis-crosslinked PA (in which NP aggregates are proposed to form elastically effective clusters). The loss modulus for HNCs reflects adsorption/desorption and friction at the NP surfaces, varying with the NP, monomer and crosslinker concentrations. Silica NPs were also found to slow the polymerization and crosslinking of acrylamide according to the specific NP surface area (set by the NP size and concentration), suggesting that silica NPs reduce the free-radical concentration.

3D printing of an interpenetrating network hydrogel material with tunable viscoelastic properties

Interpenetrating network (IPN) hydrogel materials are recognized for their unique mechanical properties. While IPN elasticity and toughness properties have been explored in previous studies, the factors that impact the time-dependent stress relaxation behavior of IPN materials are not well understood. Time-dependent (i.e. viscoelastic) mechanical behavior is a critical design parameter in the development of materials for a variety of applications, such as medical simulation devices, flexible substrate materials, cellular mechanobiology substrates, or regenerative medicine applications. This study reports a novel technique for 3D printing alginate-polyacrylamide IPN gels with tunable elastic and viscoelastic properties. The viscoelastic stress relaxation behavior of the 3D printed alginate-polyacrylamide IPN hydrogels was influenced most strongly by varying the concentration of the acrylamide cross-linker (MBAA), while the elastic modulus was affected most by varying the concentration of total monomer material. The material properties of our 3D printed IPN constructs were consistent with those reported in the biomechanics literature for soft tissues such as skeletal muscle, cardiac muscle, skin and subcutaneous tissue.

Superabsorbent enhanced-catalytic core/shell nanocomposites hydrogels for efficient water decolorization

In-situ inverse-emulsion polymerization and crosslinking of acrylamide in presence of metal oxides nanoparticles producing core/shell hydrogel nanocomposites for water decolorization.

Tunable stress relaxation behavior of an alginate-polyacrylamide hydrogel: comparison with muscle tissue.

Factors controlling the time-dependent mechanical properties of interpenetrating network (IPN) hydrogel materials are not well understood. In this study, alginate-polyacrylamide IPN were synthesized to mimic the stress relaxation behavior and elastic modulus of porcine muscle tissue. Hydrogel samples were created with single-parameter chemical concentration variations from a baseline formula to establish trends. The concentration of total monomer material had the largest effect on the elastic modulus, while concentration of the acrylamide cross-linker, N,N-methylenebis(acrylamide) (MBAA), changed the stress relaxation behavior most effectively. The IPN material was then tuned to mimic the mechanical response of muscle tissue using these trends. Swelling the hydrogel samples to equilibrium resulted in a dramatic decrease in both elastic modulus and stress relaxation behavior. Collectively, the results demonstrate that alginate-polyacrylamide IPN hydrogels can be tuned to closely mimic both the elastic and the viscoelastic behaviors of muscle tissue, although swelling detrimentally affects these desired properties.

PH‐sensitive crosslinked guar gum‐based superabsorbent hydrogels: Swelling response in simulated environments and water retention behavior in plant growth media

ABSTRACTCrosslinked guar gum‐g‐polyacrylate (cl‐GG‐g‐PA) superabsorbent hydrogels were prepared to explore their potential as soil conditioners and carriers. The hydrogels were prepared by in situ grafting polymerization and crosslinking of acrylamide onto a natural GG followed by hydrolysis. Microwave‐initiated synthesis under the chosen experimental conditions did not exhibit any significant improvement over the conventional technique. The optimization studies of various synthesis parameters, namely, monomer concentration, crosslinker concentration, initiator concentration, quantity of water per unit reaction mass, particle size of backbone, and concentration of alkali were performed. The hydrogels were characterized by wide‐angle X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and solid‐state 13C‐NMR spectroscopy. Swelling behavior of a candidate hydrogel [GG‐superabsorbent polymer (SAP)] in response to external stimuli, namely, salt solutions, fertilizer solutions, temperature, and pH, was studied. The GG‐SAP exhibited significant swelling in various environments. The effect of GG‐SAP on water absorption and the retention characteristics of sandy loam soil and soil‐less medium were also studied as a function of temperature and moisture tensions. The addition of GG‐SAP significantly improved the moisture characteristics of plant growth media (both soil and soil‐less), showing that it has tremendous potential for diverse applications in moisture stress agriculture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41060.

Property and Application of BACy‐Based Functional Hydrogels

AbstractConventional polyacrylamide hydrogels prepared from the free radical polymerization between acrylamide and N,N′‐methylenebisacrylamide (NMBA) have been frequently used in the biochemical technique like the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE) to resolve protein mixtures. In this study, we have prepared an alternative polyacrylamide hydrogel from the cross‐linking of acrylamide and N,N′‐bisacrylylcystamine (BACy). In addition, we have compared the BACy‐based hydrogel with the NMBA‐based polyacrylamide hydrogel for their physical properties such as swelling ratio, shear modulus, crosslink density and morphology. Moreover, we further determined whether BACy‐based polyacrylamide hydrogel could be applied to SDS‐PAGE and proteomics research. The results showed that this type of hydrogel is capable of separating proteins and facilitates further in‐gel protein digestion and the following protein identifications by mass spectrometry. In summary, our study provides a basis for the putative application of BACy‐based hydrogels.

Enhanced adsorption of synthetic dyes from aqueous solution by a semi-interpenetrating network hydrogel based on starch

Several semi-interpenetrating network (Semi-IPN) hydrogels were synthesized by free radical copolymerization of acrylamide, hydroxyethyl methacrylate and N′N′-methylene bis acrylamide crosslinker (MBA) in presence of starch. These hydrogels were characterized by FTIR, DTA-TGA, XRD and SEM. The hydrogel showing the highest swelling% in water was used for removal of low (2.5–40mg/L) and high (200–500mg/L) concentration range of malachite green and methyl violet dyes from water. The hydrogel showed high adsorption for both of these dyes. Isotherms, kinetics, mass transfer coefficients and thermodynamics of dye adsorption were also studied.

Thermal responsive hydrogels based on semi interpenetrating network of poly(NIPAm) and cellulose nanowhiskers

A hybrid hydrogel nanocomposite was developed based on semi interpenetrating network that was formed as a result of concurrent free radical polymerization of N-isopropylacrylamide (NIPAm) and methylenebis acrylamide (MBA) crosslinker along with cellulose nanowhiskers (CNWs). CNWs were synthesized through sulfuric acid hydrolysis and used in preparation of semi interpenetrating network (IPN). CNWs have considered as reinforcement materials for poly(NIPAm) because CNWs were distributed as strengthening entities in Poly(NIPAm). N-isopropylacrylamide was polymerized in presence of methylenebis acrylamide crosslinking agent using K2S2O8 as initiator at 700C for 1h. The resulting hydrogel's structure, morphology, thermal sensitive property and swelling behavior were investigated. It was found that introducing CNWs into Poly(NIPAm) causes a huge increase in the value of equilibrium swelling ratio (ESR) as compared with the pure PNIPAm. The ESR ranges from 21.6g/g to 5g/g as the swelling temperature changes from 310°C to 340°C; hence, the hydrogel exhibits a good responsive temperature at about 320°C.

Toward Controlling the Formation, Degradation Behavior, and Properties of Hydrogels Synthesized by Aza‐Michael Reactions

AbstractThe aza‐Michael reaction of amino‐functionalized polymers with acrylate and acrylamide crosslinkers for the formation of hydrogels is investigated. It is studied how far the reaction conditions (pH value, chemical structures of the compounds involved) influence the crosslinking and degradation rate of the gels. When crosslinking the polymer poly(1‐glycidylpiperazine), high pH values lead to fast crosslinking. Fast degradation of β‐aminoester crosslinks is observed when acrylate crosslinkers are used due to a neighboring group effect. With acrylamide crosslinkers, hydrolytically stable gels are formed, in which the shear moduli and swelling ratio can be adjusted and in which the extracts show no toxic effect on primary human fibroblasts, making them a promising material for biotechnological applications.magnified image

Micron-size metal-binding hydrogel particles improve germination and radicle elongation of Australian metallophyte grasses in mine waste rock and tailings

Metal contamination of landscapes as a result of mining and other industrial activities is a pervasive problem worldwide. Metal contaminated soils often lack effective vegetation cover and are prone to contaminant leaching and dispersion through erosion, leading to contamination of the environment. Metal-binding hydrogel particle amendments could ameliorate mine wastes prior to planting and enhance seedling emergence. In this study, micron-size thiol functional cross-linked acrylamide polymer hydrogel particles (X3) were synthesised and tested in laboratory-scale experiments on phytotoxic mine wastes to determine their capacity to: (i) increase substrate water holding capacity (WHC); (ii) reduce metal availability to plants to below the phytotoxicity threshold; and (iii) enhance germination characteristics and early radicle development of two Australian metallophyte grasses under limiting and non-limiting water conditions.Addition of X3 to mine wastes significantly increased their WHC and lowered toxic soluble metal concentrations in mine waste leachates. Germination percentages and radicle elongation of both grasses in wastes were significantly increased. Highest germination percentages and greater radicle development recorded in X3 amended wastes under water limited conditions suggests that X3 was able to ameliorate metal toxicity to radicles, and provide moisture, which improved the imbibition and consequent germination of the seeds.