Acrylic Acid Hydrogel Research Articles

Fabrication of magnetic macroporous chitosan-g-poly (acrylic acid) hydrogel for removal of Cd2+ and Pb2+

A novel macroporous magnetic macroporous chitosan-g-poly (acrylic acid) hydrogel adsorbent was fabricated from the Pickering high internal emulsions template stabilized by modified Fe3O4 nanoparticles. The structure and composition of modified Fe3O4 and macroporous magnetic hydrogel were characterized by TEM, XRD, TG and SEM techniques. The characterization results suggest that the Fe3O4 nanoparticles have been modified successfully with organosilane of 3-aminopropyltrimethoxysilane (APTES), and the porous structure of the macroporous hydrogel can be tuned with the amount of stabilized particles, volume fraction of dispersed phase and the amount of the cosurfactant. Adsorption experiments indicate that the adsorption equilibrium was rapidly reached within 20min and the maximal adsorption capacities were determined to be 308.84mg/g for Cd2+ and 695.22mg/g for Pb2+. After five adsorption–desorption cycles, the adsorbent can retain its high adsorption capacity. The introduction of Fe3O4 is beneficial to the recycle of adsorbent after usage.

Cross‐Linked Sodium Alginate‐g‐poly(Acrylic Acid) Structure: A Potential Hydrogel Network for Controlled Delivery of Loxoprofen Sodium

AbstractA series of sodium alginate‐graft‐poly(acrylic acid) hydrogels (SA‐g‐pAA hydrogels) were synthesized with sodium alginate (SA) and acrylic acid (AA) in aqueous solution, ethylene glycol dimethacrylate (EGDMA) as a cross‐linker and ammonium peroxodisulfate (APS) as an initiator. Hydrogels were evaluated for thermal stability (TGA & DSC), revealing their higher strength toward thermal variation as compared to individual components. SEM micrographs show smooth and solid outer surface with a lack of porosity on it. FTIR results revealed the grafting reaction of AA on SA. Hydrogels were then evaluated for pH responsive behavior by equilibrium swelling ratio and swelling dynamics at low and high pH. Furthermore, these cross‐linked networks were also tested for the release of Loxoprofen sodium hydrate (LSH). Drug was loaded by diffusion method and showed pH‐dependent drug release characteristics. Korsmeyer–Peppas model is the best fit model to explain drug release from the cross‐linked network. Maximum swelling, drug loading, and release has been observed at pH 7.4. It is concluded that highly stable SA and AA based polymeric matrixes are developed. These polymeric matrixes have potential to be used as a carrier for controlled delivery of LSH.

Selective adsorption and reusability behavior for Pb2+ and Cd2+ on chitosan/poly(ethylene glycol)/poly(acrylic acid) adsorbent prepared by glow-discharge electrolysis plasma

Using Pearson’s hard and soft acids and bases (HSAB) principle as the design guideline, a novel chitosan/poly(ethylene glycol)/poly(acrylic acid) (CS/PEG/PAA) hydrogel adsorbent containing hard Lewis base adsorption site (i.e., amino group, hydroxyl group, ether linkage, carboxylate ions) was prepared by glow-discharge electrolysis plasma (GDEP) technique and then applied for the selective adsorption of Pb2+. A copolymerization mechanism initiated by GDEP was proposed. The structure, thermal stability, and morphology of CS/PEG/PAA adsorbent were characterized by FT-IR, thermogravimetry/differential thermogravimetry (TG/DTG), and SEM. The effects of the solution pH and contact time on the single-component adsorption were examined by batch experiments. Competitive adsorptions of Pb2+ and Cd2+ were carried out under equal mass concentration and equal molar concentration. In addition, regeneration and reusability of adsorbent were also investigated in detail. The results showed that the maximum adsorption capacities for Pb2+ and Cd2+ are 431.7 and 265.0 mg g−1, respectively. The kinetic behaviors of the adsorption and the fourth desorption for single component and the competitive adsorption for Pb2+ follow the pseudo-second-order model with pH = 4.8. The CS/PEG/PAA adsorbent has good adsorption selectivity for Pb2+ with the coexistence of Cd2+. The adsorbent displays excellent regeneration and reusability in the EDTA-4Na solution.

Synthesis and Characterization of Graft Copolymers of Acrylic Acid onto Starch

A novel starch-g-poly (acrylic acid) hydrogel was prepared by graft-copolymerization among starch, acrylic acid in aqueous solution with potassium persulfate as an initiator, N, N-methylenebisacrylamide as a crosslinking agent. Characterization of the graft copolymer was carried out by X-ray diffraction, FTIR and SEM analytical methods. Swelling kinetic analysis in distilled water was done to study the swelling behavior of the product. The results show that the product exhibits water absorption of 786g/g in distilled water at ambient temperature. It has been proved that the grafting of acrylic acid onto starch was successful and the aggregation of phase of native starch was changed from semi-crystalline state to amorphous aggregation state due to copolymerization.

Tensiometric and Phase Domain Behavior of Lung Surfactant on Mucus-like Viscoelastic Hydrogels.

Lung surfactant has been observed at all surfaces of the airway lining fluids and is an important contributor to normal lung function. In the conducting airways, the surfactant film lies atop a viscoelastic mucus gel. In this work, we report on the characterization of the tensiometric and phase domain behavior of lung surfactant at the air-liquid interface of mucus-like viscoelastic gels. Poly(acrylic acid) hydrogels were formulated to serve as a model mucus with bulk rheological properties that matched those of tracheobronchial mucus secretions. Infasurf (Calfactant), a commercially available pulmonary surfactant derived from calf lung extract, was spread onto the hydrogel surface. The surface tension lowering ability and relaxation of Infasurf films on the hydrogels was quantified and compared to Infasurf behavior on an aqueous subphase. Infasurf phase domains during surface compression were characterized by fluorescence microscopy and phase shifting interferometry. We observed that increasing the bulk viscoelastic properties of the model mucus hydrogels reduced the ability of Infasurf films to lower surface tension and inhibited film relaxation. A shift in the formation of Infasurf condensed phase domains from smaller, more spherical domains to large, agglomerated, multilayer structures was observed with increasing viscoelastic properties of the subphase. These studies demonstrate that the surface behavior of lung surfactant on viscoelastic surfaces, such as those found in the conducting airways, differs significantly from aqueous, surfactant-laden systems.

Structural Response of Imogolite–Poly(acrylic acid) Hydrogel under Deformation

The structures of imogolite–poly(acrylic acid) hydrogels were investigated using small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) to determine the effects of particle concentration and the magnitude of deformation. The imogolite–poly(acrylic acid) hydrogel was synthesized by using γ-ray radiation as a nanocomposite gel with chemical bonds between the particles and polymers. The SAXS measurements revealed that the imogolite network was composed of particle overlaps. Under deformation, the gel structure was rearranged to increase the dimensionality of the network, forming a relaxed structure of overlaps by changing the orientation of the imogolite. The structural response of the deformed gel depended on the imogolite concentration, which influenced the changes in dimensionality of the network and the number of overlaps. The SANS patterns indicated that the polymers wrapped the imogolite aggregates, allowing polymers to follow the imogolite behavior. These observations demonstrat...

Interconnectivity of Macroporous Hydrogels Prepared via Graphene Oxide-Stabilized Pickering High Internal Phase Emulsions.

Interconnected macroporous poly(acrylic acid) (PAA) hydrogels are prepared via oil-in-water (o/w) Pickering high internal phase emulsion (HIPE) templates stabilized by graphene oxide (GO). The amphiphilicity of GO is adjusted by slight modification with cetyltrimethylammonium bromide (CTAB). The morphology of macroporous PAA is observed by a field-emission scanning electron microscope (FE-SEM). The gas permeability is characterized to evaluate the interconnectivity of polymer foams. The pore and pore throat size can be tailored by varying the wettability and concentration of GO. The selective adsorption toward dyes of PAA hydrogels is proved. Macroporous PAA hydrogels with an open-cell structure show enhanced adsorption behavior of both methylene blue (MB) and copper(II) ions.

Kinetics of Exchange of the Water Absorbed in Poly (Acrylic Acid) Hydrogel with Ethanol

Kinetics of Exchange of the Water Absorbed in Poly (Acrylic Acid) Hydrogel with Ethanol

Dually cross-linked single network poly(acrylic acid) hydrogels with superior mechanical properties and water absorbency.

Poly(acrylic acid) (PAA) hydrogels with superior mechanical properties, based on a single network structure with dual cross-linking, are prepared by one-pot free radical polymerization. The network structure of the PAA hydrogels is composed of dual cross-linking: a dynamic and reversible ionic cross-linking among the PAA chains enabled by Fe(3+) ions, and a sparse covalent cross-linking enabled by a covalent cross-linker (Bis). Under deformation, the covalently cross-linked PAA chains remain intact to maintain their original configuration, while the Fe(3+)-enabled ionic cross-linking among the PAA chains is broken to dissipate energy and then recombined. It is found that the mechanical properties of the PAA hydrogels are significantly influenced by the contents of covalent cross-linkers, Fe(3+) ions and water, which can be adjusted within a substantial range and thus broaden the applications of the hydrogels. Meanwhile, the PAA hydrogels have excellent recoverability based on the dynamic and reversible ionic cross-linking enabled by Fe(3+) ions. Moreover, the swelling capacity of the PAA hydrogels is as high as 1800 times in deionized water due to the synergistic effects of ionic and covalent cross-linkings. The combination of balanced mechanical properties, efficient recoverability, high swelling capacity and facile preparation provides a new method to obtain high-performance hydrogels.

Enhanced drug release by selective cleavage of cross-links in a double-cross-linked hydrogel

Poly(acrylic acid) hydrogels were synthesized using two different cross-linking agents namely, cystamine and Jeffamine. The redox sensitive di-sulfide linkages could be selectively cleaved to enhance the release of doxorubicin.

Adsorption of Cu(II) ion from aqueous solutions on hydrogel prepared from Konjac glucomannan

A novel adsorbent, biodegradable Konjac glucomannan-poly(acrylic acid) (KGMP) hydrogel, is prepared by Konjac glucomannan grafting with acrylic acid. The adsorption properties of the KGMP for Cu(II) ion removal from aqueous solutions are investigated. The experiments are performed under various impact factors such as initial Cu(II) ion concentration, pH, contact time, temperature and salt ionic strength. The Langmuir and Freundlich isotherm are employed to discuss the adsorption behavior. The result shows the equilibrium data obtained at different temperatures are represented perfectly by Langmuir isotherm model compared to the Freundlich isotherm models. The monolayer saturation adsorption capacities of KGMP for Cu(II) ion is found to be 27.1739, 30.2115, 34.1297 and 41.6667 mg g−1 at 298, 303, 308 and 313 K, respectively. Thermodynamic parameters such as ΔG, ΔH and ΔS are calculated. The kinetics studies show that adsorption process follows the pseudo-second-order model and the adsorption process is mainly controlled by both surface reactivity and intra-particle diffusion. FT-IR analysis shows that a large number of carbonyl, ester, and hydroxyl groups are included in the external surface of the KGMP, SEM indicates that the rough, irregular and pores of different size and shapes on surfaces of the KGMP are observed before adsorption. The present study indicates that the KGMP is an effective adsorbent for the removal of Cu(II) ion from aqueous solutions.

Preparation and electro-response of chitosan-g-poly (acrylic acid) hydrogel elastomers with interpenetrating network

In this article, novel chitosan-g-poly (acrylic acid) hydrogel elastomers were successfully sythesised by grafting chitosan (CTS) onto poly acrylic acid (PAA) through radical polymerization in the presence/absence of direct current electric field. Their structure and electro-response were evaluated through scanning electron microscopy (SEM), infrared spectroscopy (IR), and dynamic mechanical analyser (DMA), respectively. Stress-strain test showed that the toughness of the chitosan-g-PAA elastomer is higher than the PAA gel. The result demonstrates the elastomers obtained in the presence/absence of electric field with similar chemical composition possess different microstructure. The positive electro responsive effect appeared on the elastomers, and both of storage modulus increment and increment sensitivity yielded maximum value at the AA concentration of 14.09 wt% under the applied electric field of 1.5 kV/mm. Thermo gravimetry and differential scanning calorimetry (TG-DSC) showed the elastomers cured under an applied electric field have stronger intramolecular bonding and higher cross-linking density.

Hyperbranched polyglycerol/poly(acrylic acid) hydrogel for the efficient removal of methyl violet from aqueous solutions

ABSTRACTHydrogels were synthesized from hyperbranched polyglycerol (HPG) and acrylic acid through free‐radical polymerization with HPG as the crosslinker. The HPG/poly(acrylic acid) (PAA) hydrogel could absorb cationic dyes in aqueous solutions because of the existence of a porous structure and the large numbers of hydroxyl and carboxylic groups. With methyl violet chosen as a model compound, the HPG/PAA hydrogel reached a maximum adsorption of 394.12 mg/g at a feed concentration of 1 g/L. The highest removal ratio of 98.33% was observed at a feed concentration of 50 mg/L. The effects of the pH, contact time, and feed concentration on the dye adsorption were investigated. The dye adsorption data fit well with the pseudo‐second‐order and Langmuir models. We believe that the HPG/PAA hydrogels could perform well in appropriate applications in the removal of cationic dyes from aqueous solutions because of their high adsorption capacity and environmental friendliness. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42951.

Formation of chemical networks of acrylamide and acrylic acid hydrogels initiated by ammonium persulfate

The process of crosslinking in hydrogels of polyacrylamide, poly(acrylic acid), and their copolymers that is initiated by ammonium persulfate is studied. It is shown that, when the threshold concentration of ammonium persulfate, which amounts to 3 mmol/L for PAcA and 18 mol/L for poly(acrylic acid), is exceeded, the chemical network of the gel is formed. A mechanism is advanced to explain the formation of junctions in the chemical networks of polyacrylamide and poly(acrylic acid) gels. It is based on the reaction of chain transfer involving the hydrogen atom in the α position relative to the functional groups of a chain. With the use of the Flory–Rehner equation, the degrees of polymerization of network subchains are calculated. Effects of the temperature of synthesis, the concentration of ammonium persulfate, and the composition of the monomer mixture on the degrees of swelling of the resulting gels are examined. The degrees of swelling of polyacrylamide gels filled with nanodispersed zirconia powder are measured. It is found that in the presence of the filler, the formation of the chemical network initiated by ammonium persulfate may be one of the important factors affecting gelation.

Lignocellulosic biomass for the preparation of cellulose‐based hydrogel and its use for optimizing water resources in agriculture

ABSTRACTRecently, efforts have been devoted to find ways in utilizing biomass as feedstocks for the production of organic chemicals. This is because of its abundance, renewability and worldwide distribution. Lignocellulosic agricultural waste materials are regarded as abundant, inexpensive, and readily available natural resources for both chemical and paper industries. Hydrogels are polymeric materials that vary in their origin and composition and can absorb large amount of water without dissolving. In our study, cellulose‐based acrylic acid hydrogel was synthesized starting from rice straw as a source for the lignocellulosic material, where cellulose was first isolated after alkaline‐acid pulping treatment followed by bleaching step with sodium hypochlorite resulting of 90.8% holocellulose. The cellulose‐based acrylic acid hydrogel was synthesized applying heterogeneous reaction and shows a swelling ratio more than 3000%. The resulting hydrogel was further characterized with FT‐IR and SEM. On the other hand, comparison between the rice straw‐based hydrogel and the commercially available acrylamide hydrogel was studied for improving maize production in salt affected soil as well as in the growth promoters of maize under water stress. The experimental results demonstrated that the yield parameters were increased with increasing irrigation rates. Both types of hydrogels introduce positive and significant effect compared to the one without adding hydrogels. Also, acrylamide hydrogel was effective for improving almost yield parameters more than applying rice straw‐based hydrogel. Generally, the addition of hydrogel increases the nutrient concentration, uptake, and both of water and nutrients use efficiency. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42652.

Controlled release of anti-diabetic drug Gliclazide from poly(caprolactone)/poly(acrylic acid) hydrogels

Drug Gliclazide (Glz) has limited solubility and low bioavailability. In order to obtain a controlled release of this drug and to improve its bioavailability, the drug has been loaded into poly(caprolactone) (PCL)/poly(acrylic acid) (PAAc) hydrogels, prepared by free radical polymerization of acrylic acid in the presence of poly(caprolactone) in acetone medium using azo-isobutyronitrile as initiator and N,N′ methylene bisacrylamide as cross-linking agent. The swelling behaviour of these hydrogels has been investigated in the physiological gastric and intestinal fluids to obtain an optimum composition suitable for delivery of a biologically active compound. The gels were loaded with anti-diabetic drug Glz and a detailed investigation of release of drug has been carried out. Various kinetic models have been applied on the release data. Finally, the Albino wistar rats were treated for Streptozotocin plus nicotinamide – induced diabetes using a Glz-loaded PCL/PAAc hydrogel. The results indicated a fair reduction in the glucose level of rats.

Preparation and Characterization of Isosorbide Mononitrate Hydrogels Obtained by Free-Radical Polymerization for Site-Specific Delivery

Purpose: To prepare and characterize acrylic acid and ethyl cellulose hydrogels of isosorbide mononitrate for site-specific delivery.Methods: Free radical polymerization method was employed using benzoyl peroxide as initiator and N, N’-Methylenebisacrylamide (MBA) crosslinked copolymer of ethyl cellulose and acrylic acid. Benzyl peroxide and N, N'-Methylenebisacrylamide in varying amounts were dissolved in acrylic acid. The two solutions were mixed together to a final weight of 100 g. Hydrogels were evaluated for sol-gel characteristics, diffusion coefficient, and porosity. Hydrogel formation was examined by FTIR while drug loading efficiency study was carried out using 1 % (w/v) drug solution.Results: Swelling and drug release decreased with increasing acrylic acid and MBA concentrations due to high degree of crosslinking. Increasing acrylic acid content of hydrogel produced a decrease in drug release from 29.89 to 25.79 %, 75.37 to 67.87 % and 84.91 to 75.85 % at pH 1.2, 6.5 and 7.5, respectively. Remarkably, high swelling was observed at higher pH. Gel fraction and porosity results showed that acrylic acid and crosslinker raised gel fraction but reduced porosity, while ethyl cellulose exhibited a reverse effect. FTIR confirmed graft copolymer formation.Conclusion: Isosorbide mononitrate hydrogels prepared with crosslinked copolymer of ethyl cellulose and acrylic acid can be suitably formulated for targeted delivery of the drug to the small intestine.Keywords: N, N'-Methylenebisacrylamide, Ethyl cellulose, Acrylic acid, Isosorbide mononitrate, Free radical polymerization, Graft copolymer, Site-specific delivery, Hydrogel, pH-sensitive

Translational and rotational motion control of microgels enabling shoaling and schooling.

A technique for adequate flow control is important in the fields of science and engineering. In this study, we hypothesized that the unrestricted flow control inside a chamber containing 'schools of magnetic particles' might be possible through control of an external magnetic field, biomimicking the flow generated by schools of fish. Microgels based on superparamagnetic iron oxide nanoparticles (SPIONs) and poly(acrylic acid) hydrogels were employed. With an increase in the SPION content, the microgels responded more efficiently to the translational movement of the magnetic field. Rotational movement was more efficiently achieved with anisotropic distribution of SPIONs inside microgels, which was induced by applying a magnetic field immediately prior to crosslinking. The systems of the anisotropic microgels successfully provided microflow for effective mixing in a capillary. This biomimetic flow control may be useful for the control of fluid systems of any micro- or nano-size and any shape, regardless of the tortuosity.

Preparation and characterization of a novel pH-sensitive Salecan-g-poly(acrylic acid) hydrogel for controlled release of doxorubicin.

Salecan is a novel water-soluble extracellular β-glucan produced by a salt-tolerant strain Agrobacterium sp. ZX09. Salecan is suitable for the fabrication of hydrogels for biomedical applications due to its excellent physicochemical and biological properties. In this paper, a series of pH-sensitive hydrogels were prepared in aqueous solution by the graft copolymerization of Salecan and acrylic acid (AA) using N,N'-methylene diacrylamide as a crosslinker for controlled drug delivery. The structure and thermal stability of the resulting hydrogels were characterized by FT-IR, XRD and TGA. By SEM analysis, freeze-dried hydrogels displayed an interconnected porous structure with tunable pore size in the range of 23.2-90.3 μm. The swelling behavior of the hydrogels was shown to be highly dependent on the environmental pH, salt type and concentration, as well as the contents of Salecan and BAAm. They are almost unswellable at pH 1.2 and swollen extensively at pH 6.86. Meanwhile, the increase in the content of hydrophilic Salecan could enhance the swelling ratio, whereas the presence of more BAAm reduced the swelling capacity but promoted the water retention to some extent. Rheological tests revealed that storage modulus G' was strongly influenced by the crosslink density of the obtained hydrogel network. Especially, doxorubicin (DOX) as a model anti-cancer drug was very efficiently loaded into the negatively charged hydrogels (up to 69.4 wt%) through electrostatic interactions. More importantly, the release of DOX from this intelligent system exhibited pH-responsive behavior and a sustained release pattern. For SPA2, the cumulative release profile showed a low level of drug release (about 12.3 wt% in 24 h) at pH 7.4, and was significantly accelerated at pH 4.0 (over 40 wt% in 6 h). Cytotoxicity experiments confirmed that all blank hydrogels were non-toxic to A549 cells, while DOX released from the drug-loaded hydrogels remained biologically active and had the capability to kill cancer cells. The preliminary results clearly suggested that the Salecan-g-PAA hydrogels may be promising carriers for controlled drug delivery.

Radiation crosslinked swellable ionic gels: equilibrium and kinetic studies of basic dye adsorption

High-energy gamma radiation was employed to synthesize acrylic acid (AA)-based simple hydrogel adsorbent for environmental remediation of dye effluent. The adsorbent was tested for the aqueous solutions of two basic dyes, namely, Basic red 29 (BR 29) and Methylene blue (MB). The AA concentration of 20% (w/v) and absorbed dose of 30 kGy were optimized to synthesize AA hydrogel having good strength, and faster uptake kinetics for a wide range of dye concentration (10–5,000 mg/L). Equilibrium adsorption of both the dyes BR 29 and MB were better described by Langmuir adsorption. The equilibrium dye adsorption capacity onto AA hydrogel was found to be very high i.e. 1,123 mg/g (or 3.04 mmol/g) and 220 mg/g (or 0.68 mmol/g) for BR 29 and MB, respectively. The adsorption of BR 29 onto AA hydrogel followed the pseudo-first-order kinetics only in the initial time scale, whereas the adsorption of MB on AA hydrogel followed pseudo-second-order kinetics over the entire range of adsorption process. Desorption studies helped to elucidate the mechanism of dye adsorption and recycling of the spent adsorbent. The overall adsorption–desorption studies of these dyes on simple AA-based hydrogels are quite encouraging for more exploration.