Acrylic Hydrogels Research Articles

Experimental investigation of the mechanical behavior of a poly(acrylamide-co-sodium acrylate) hydrogel

Stimuli-responsive hydrogels consist of a porous 3D framework that is saturated with solvent. Immersed in a solution bath, these gels can exhibit an enormous volume change due to absorption or release of solution. Depending on the type of gel, this effect can be generated for example by variation of the ion concentration in the surrounding solution bath or by an applied electrical field. The mechanical behavior of these polymers is influenced not only by the solid-state skeleton, but also by the interacting fluid. Thus, a visco-elastic behavior can be observed on the macroscopic scale. Based on the specific properties of the polymer gel and the interaction of the different phases, the determination of the mechanical properties of this material turns out to be non-trivial. In the present work, the mechanical behavior of a poly(acrylamide-co-sodium acrylate) hydrogel in the fully swollen state is investigated by a newly developed tensile test and for longtime investigations by a creep test. For this purpose, two newly developed different experimental setups based on digital image correlation are used.

Enhanced removal of oxytetracycline antibiotics from water using manganese dioxide impregnated hydrogel composite: Adsorption behavior and oxidative degradation pathways

The present work provides the first attempt of using manganese dioxide loaded poly(sodium acrylate) hydrogel (MnO2@PSA) to address potential threats posed by oxytetracycline (OTC) antibiotics in aqueous environment. The MnO2@PSA was prepared via a facile approach and demonstrated enhanced removal performance even under extremely high concentrations of OTC. The outstanding performance exhibited by MnO2@PSA was attributed to synergetic effects of adsorption oxidative degradation. The synthesized composite was characterized evaluated under varying conditions. The adsorption pH was optimized at pH 5, at which the removal efficiency OTC was reached 91.46%. According to the kinetics study, the pseudo-second-order kinetic model was the best to explain the adsorption data, implying the interaction mechanisms were dominated by chemisorption. The Langmuir isotherm model was the best to explain the isotherm data, and the corresponding maximum adsorbed amount of OTC was 1150.4 mg g−1. The MnO2@PSA was highly selective for OTC adsorption and degradation under the presence of natural organic matter and common environmental metal ions. The oxidative degradation study indicated that OTC molecules were structurally degraded into 15 intermediate products via six reaction pathways. Both the theoretical models and spectroscopic methods demonstrated the removal mechanism of OTC onto MnO2@PSA was governed by ion exchange, cation-π bonding, hydrogen-bonding, and π-π electron donor-acceptor. Overall, MnO2@PSA is an excellent and environmentally sustainable material to remove OTC from water and wastewater via the combined effects of adsorption and oxidative degradation.

Radiation initiated synthesis, characterization, and swelling behavior of poly (acrylic acid‐co‐acrylamide)/starch grafted hydrogel

AbstractThe powerful waves of ultrasound are used in polymerization reactions in the absence of initiator. In the present research, the hydrogel was obtained by water‐soluble acrylic monomers, starch, and the crosslinking agent of methylene bis acrylamide dissolved in water/glycerol dual. The hydrogel is formed by these waves only in viscous environments such as glycerol, heat, or initiator is not required. In the presence of ultrasound, the time of product formation is reduced to a few minutes. Moreover, the resulting hydrogels have more uniform microscopic structure and are more swollen. The structure of the grafted hydrogel was examined meanwhile the hydrogel swelling in three environments of pure water, saltwater, and under pressure was measured. It was found that the grafted hydrogel has double swelling rate in the pure. Also, after loading the ciprofloxacin into the synthesized hydrogel, this drug is released 99% in initial 20 min. 0.1 g starch in 1.5 g acrylic hydrogel has the most drug release. The high swelling capacity in the pH ranges of 5–9 shows the extension of drug application in acidic or alkaline environments, and also after several using the gel and the capacity of water absorbency, which was about 70% of its initial water, indicates the perfect reusability capacity of the gel.

N-isopropyl acrylamide/sodium acrylate hydrogel as draw agent for forward osmosis to concentrate esterification wastewater

N-isopropyl acrylamide/sodium acrylate hydrogel as draw agent for forward osmosis to concentrate esterification wastewater

Development of Kraft Lignin Chemically Modified as a Novel Crosslinking Agent for the Synthesis of Active Hydrogels

In this research a chemical modification of kraft lignin was carried out using a basic nucleophilic substitution reaction (NSA) in order to functionalize it as a novel crosslinking agent for the synthesis of active hydrogels. The chemical modification success of the synthesized crosslinker was demonstrated by using several techniques such as volumetry probes, FTIR, 1H-NMR and DSC. Thus, the obtained materials were employed during the synthesis of acrylic acid-based hydrogels, due to its high-water absorption capacity to evaluate their retention potential of heavy metal ions. Characterization of the active hydrogels were performed by FTIR and SEM, showing the specific signals corresponding to the base monomers into the polymer skeleton and the efficiency of modified kraft lignin as a novel crosslinking agent. Additionally, to demonstrate the potential use of these hydrogels in wastewater treatment, metal ions adsorption experiments were conducted, showing adsorption percentages higher than 90% and 80% for Pb2+ and Cu2+, respectively.

Equilibrium and kinetics study of methyl violet adsorption by pineapple leaf fibers‐cl‐poly(acrylic acid‐co‐2‐dimethyl amino ethyl acrylate) hydrogel

AbstractThe pine apple leaf fiber‐cl‐poly(acrylic acid‐co‐2‐dimethyl amino ethyl acrylate) hydrogel is prepared by crosslinked graft copolymerization of acrylic acid and 2‐(dimethyl amino) ethyl acrylate onto the pine apple leaf fibers to be used as an adsorbent for the remove dye from aqueous solutions. Several characterization techniques like Fourier transform infrared spectroscopy field emission scanning electron microscopy‐Energy‐dispersive X‐ray spectroscopy and X‐ray diffraction analysis. The synthesized hydrogel shows strong water swelling characteristics (780.93%) and also exhibits faster deswelling property. The methyl violet (MV) adsorption data are fitted well with the Freundlich isotherm model with maximum monolayer adsorption capacities 625 mg/g for MV. The equilibrium kinetics follow pseudo second order model together with intra particle diffusion, one step process. Thermodynamic parameters show that the MV adsorption by the hydrogel is spontaneous and endothermic in nature. The overall removal efficiency is found to be 98.23% under optimum condition.

Alginate Bioconjugate and Graphene Oxide in Multifunctional Hydrogels for Versatile Biomedical Applications.

In this work, we combined electrically-conductive graphene oxide and a sodium alginate-caffeic acid conjugate, acting as a functional element, in an acrylate hydrogel network to obtain multifunctional materials designed to perform multiple tasks in biomedical research. The hybrid material was found to be well tolerated by human fibroblast lung cells (MRC-5) (viability higher than 94%) and able to modify its swelling properties upon application of an external electric field. Release experiments performed using lysozyme as the model drug, showed a pH and electro-responsive behavior, with higher release amounts and rated in physiological vs. acidic pH. Finally, the retainment of the antioxidant properties of caffeic acid upon conjugation and polymerization processes (Trolox equivalent antioxidant capacity values of 1.77 and 1.48, respectively) was used to quench the effect of hydrogen peroxide in a hydrogel-assisted lysozyme crystallization procedure.

Preparation of Agave tequilana Weber nanocrystalline cellulose and its use as reinforcement for acrylic hydrogels

Nanocrystalline cellulose (NCC) was prepared from Agave tequilana Weber blue variety via acid hydrolysis. The NCC was used in forming acrylic acid/acrylamide hydrogels (AA/AM), (80/20 w/w), crosslinked with N-N-methylene bisacrylamide (MBA) at addition levels of 1, 2, 4, and 8 wt% of the monomeric phase. The NCC was dosed at 0.1, 0.5, and 1.0 wt%. Two synthesis routes were used. In the first route, polymerization was performed immediately after mixing the components. In the second route, the mixture of the components was kept at 2 °C ± 1 °C for 24 h before the polymerization (thermal treatment). All the hydrogels were characterized by nuclear magnetic resonance (NMR), water absorption tests, scanning electron microscope (SEM) analysis, and rheology tests. The NCC particles had a diameter of approximately 75 nm. The hydrogels that were subjected to the thermal treatment reached the equilibrium after approximately 72 h. The un-treated hydrogels reached the equilibrium after approximately 58 h. The thermally treated samples had a lower swelling degree and the swelling degree decreased as the crosslinking degree and the NCC concentration increased. The swelling kinetics followed the Schott´s pseudo-second-order.

Hydrous manganese dioxide modified poly(sodium acrylate) hydrogel composite as a novel adsorbent for enhanced removal of tetracycline and lead from water

In this study, hydrous manganese dioxide (HMO) modified poly(sodium acrylate) (PSA) hydrogel was produced for the first time to remove tetracycline(TC) and lead(Pb(II)) from water. The as-prepared composite was characterized using various techniques, such as SEM-EDS, FTIR, XRD, BET, and XPS, to elucidate the successful loading of HMO and analyze subsequent sorption mechanisms. Different influencing parameters such as adsorbent dose, initial concentration of adsorbates, reaction time, solution pH, and temperature were also investigated. The adsorption kinetic studies of both TC and Pb(II) removal indicated that equilibrium was achieved within 12 h, with respective removal rates of 91.9 and 99.5%, and the corresponding adsorption data were fitted to the second-order kinetics model. According to the adsorption isotherm studies, the sorption data of TC best fitted to the Langmuir isotherm model while the adsorption data of Pb(II) were explained by the Freundlich isotherm model. The maximum adsorption capacities of both TC and Pb(II) were found to be 475.8 and 288.7 mg/g, respectively, demonstrating excellent performances of the adsorbent. The uptake capacity of PSA-HMO was significantly influenced by the level of solution pH, in which optimum adsorption amount was realized at pH 4.0 in the TC and Pb(II) systems, respectively. Thermodynamic studies showed the process of TC and Pb(II) adsorptions were endothermic and spontaneous. Overall this study elucidated that PSA-HMO composite can be a promising candidate for antibiotics and heavy metal removal in water treatment applications.

Ultrahigh Adsorption Capacity of Acrylic Acid-Grafted Xanthan Gum Hydrogels for Rhodamine B from Aqueous Solution

Rhodamine B (RhB) is considered as a potential source of water pollution because it is harmful to the environment and humans, and thus, it should be removed from the water system. Hydrogels derived...

Poly (hydroxyethyl methacrylate-co-hydroxyethyl acrylate) soft contact lenses for acetazolamide release

In this study, different ratios of poly (hydroxyethyl methacrylate-co-hydroxyethyl acrylate) hydrogels (HEMA-co-HEA), corresponding to (100/0, 70/30, 60/40, 50/50, 40/60, 30/70, and 0/100) were successfully prepared by free radical polymerization leading to tunable drug release materials for therapeutic soft contact lenses (SCLs) applications. The microstructures of the materials were investigated using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), and their thermal properties were examined with differential scanning calorimetry (DSC) and thermogravimetric (TGA) analyses. The results showed that the presence of HEA in the hydrogels matrix improved the materials’ microstructure and enhanced the swelling capacity in a 0.9% NaCl solution (pH = 5.5) at 37 °C. Furthermore, in vitro study of the loading and release of acetazolamide, as a model drug, showed a non-Fickian drug release behavior for all the studied hydrogels, whereas the highest drug release/loading capacity was observed for the hydrogel ratio HEMA/HEA of 40/60. Therefore, it can be concluded that the corresponding hydrogel is a promising curative SCLs material for a sustainable drug release application.

Multimaterial Printing for Cephalopod-Inspired Light-Responsive Artificial Chromatophores.

Cephalopods use chromatophores distributed on their soft skin to change skin color and its pattern. Each chromatophore consists of a central sac containing pigment granules and radial muscles surrounding the sac. The contraction of the radial muscle causes the central sac to expand in area, making the color of the pigment more visible. With the chromatophores actuating individually, cephalopods can create extremely complex skin color patterns, which they utilize for exquisite functions including camouflage and communication. Inspired by this mechanism, we present an artificial chromatophore that can modulate its color pattern in response to light. Multimaterial projection microstereolithography is used to integrate three functional components including a photoactive hydrogel composite with polydopamine nanoparticles (PDA-NPs), acrylic acid hydrogel, and poly(ethylene glycol) diacrylate. In order to generate light-driven actuation of the artificial chromatophore, the photothermal effect of the PDA-NPs, light-responsive deformation of the photoactive hydrogel composite, and the produced mechanical stresses are studied. Mechanical properties and interfacial bonding strengths between different materials are also investigated to ensure structural integrity during actuation. We demonstrate pattern modulation of the light-responsive artificial chromatophores (LACs) with the projection of different light patterns. The LAC may suggest a new concept for various engineering applications such as the camouflage interface, biophotonic device, and flexible display.

Removal of water and their soluble materials from fuels using Moringa oleifera loaded keratin-co-sodium acrylate hydrogel

Water is inevitable in production, purification, and transportation of liquid fuels. At the same time, water in fuels is a significant concern to the fuel engines as well as storage tanks. Removing water and their soluble materials from liquid fuels, like Lemon Essential Oil (LEO), Castor oil, Pungan oil, Palm oil, Engine oil (lubricating oil 20/40), and diesel is necessary to maintain the quality of fuels and to comply with legal and commercial supplies. In this present study, a defatted Moringa oleifera seed extract loaded keratin-co-sodium acrylate hydrogel was developed for the complete removal of suspended water/moisture and water-soluble materials present in the fuel samples. Thus, a hydrophilic and highly crosslinked hydrogel was grafted for the highest water absorbing/removal from liquid fuels. In our perspective view, the best combination of synthetic and natural polymeric materials grafting hydrogel was identified via optimization technique. The experimentally optimized keratin-co-sodium acrylate hydrogel has shown the most significant property of water-absorbing capacity. Further, the results have shown and demonstrated that defatted Moringa oleifera seed extract loaded keratin-co-sodium acrylate hydrogel absorbed/removed ~95% water, and keratin-co-sodium acrylate hydrogel was ~90% from fuel samples. Furthermore, the observed results indicated that defatted M. oleifera seed extract removed unwanted water-soluble materials present in the fuel samples as compared with keratin-co-sodium acrylate hydrogel.

Copper–Calcium Poly(Acrylic Acid) Composite Hydrogels as Studied by Electron Paramagnetic Resonance (EPR) Spectroscopy

Front Cover: In article number 2000262 by Haleh H. Haeri, Dariush Hinderberger, and co-workers, incorporating copper ions into synthetic poly acrylic acid polymer hydrogels results in toughening of these hydrogels. Continuous wave and pulsed electron paramagnetic resonance spectroscopic techniques reveal that the origin of the observed boost in mechanical properties stems from parts of the hydrogel network that interact with and through hydrated copper ions.

Catalytic Reduction of Toxic Dyes Using Highly Responsive and Stable Ag Nanocomposite

The objective of study is preparing multi-responsive, nontoxic, and highly stable nanocomposite hydrogels for effective reduction and decolonization of broad spectrum of toxic dyes. The nanocomposite hydrogels are composed of N-isopropy acrylamide, acrylic acid, and silver/chitosan nano-dispersion and prepared by the effect of Gamma radiation at a dose rate of 2.6 kGy/h. The physical and chemical properties of the various prepared nanocomposites hydrogels were studied by various techniques as SEM, TEM, XRD, and FTIR. The swelling properties of the nanocomposites hydrogels were studied under various conditions as pH and temperature. Given the physical properties of multifunctional thermo-responsive N-isopropy acrylamide, acrylic acid hydrogel, and its Ag nanocomposite, they hold the strong potential for toxic dyes degradation as Erioglaucine as a model dye. In this paper, we review various silver and thermo-responsive poly (N- isopropylacrylamide/Acrylicacid /silver), (PNIPAM/AA/Ag) nanocomposites and highlight their high activity as a catalyst for degradation of various types of dyes.

Biosafety of a 3D-printed intraocular lens made of a poly(acrylamide-co-sodium acrylate) hydrogel in vitro and in vivo.

To assess the biosafety of a poly(acrylamide-co-sodium acrylate) hydrogel (PAH) as a 3D-printed intraocular lens (IOL) material. The biosafety of PAH was first evaluated in vitro using human lens epithelial cells (LECs) and the ARPE19 cell line, and a cell counting kit-8 (CCK-8) assay was performed to investigate alterations in cell proliferation. A thin film of PAH and a conventional IOL were intraocularly implanted into the eyes of New Zealand white rabbits respectively, and a sham surgery served as control group. The anterior segment photographs, intraocular pressure (IOP), blood parameters and electroretinograms (ERG) were recorded. Inflammatory cytokines in the aqueous humor, such as TNFα and IL-8, were examined by ELISA. Cell apoptosis of the retina was investigated by TUNEL assay, and macroPAHge activation was detected by immunostaining. PAH did not slow cell proliferation when cocultured with human LECs or ARPE19 cells. The implantation of a thin film of a 3D-printed IOL composed of PAH did not affect the IOP, blood parameters, ERG or optical structure in any of the three experimental groups (n=3 for each). Both TNFα and IL-8 in the aqueous humor of PAH group were transiently elevated 1wk post-operation and recovered to normal levels at 1 and 3mo post-operation. Iba1+ macroPAHges in the anterior chamber angle in PAH group were increased markedly compared to those of the control group; however, there was no significant difference compared to those in the IOL group. PAH is a safe material for 3D printing of personal IOLs that hold great potential for future clinical applications.

Controlling radiation degradation of aCMCsolution to optimize the swelling of acrylic acid hydrogel as water and fertilizer carriers

A copolymer hydrogel consisting of Polyacrylic Acid (PAAc) combined with an irradiated solution of carboxymethyl cellulose (CMC, 1 wt%) was prepared. The focus was on controlling the radiation degradation of CMC by exposing it to different six doses of γ‐irradiation from 0 up to 3 kGy. After the irradiation process, the six CMC solution samples were mixed with 10 vol% of Acrylic Acid (AAc) monomer and re‐irradiated at a dose of 25 kGy to begin the polymerization process. A scanning electron microscope (SEM) was used to image the macroporous structure of the obtained (CMC/PAAc) hydrogel. Moreover, the SEM image confirmed the interpenetrating and semi‐interpenetrating polymer network structure based on the irradiation process. The controlled release of urea is achieved due to the binding between urea and the functional groups of the investigated hydrogel by hydrogen bonds. The growth of common bean plant (Phaseolus vulgarisL.) and chlorophyll contents were increased when soils were treated with (CMC/PAAc) compared with soils with free hydrogel in water‐stress conditions.

Hidrogel acrilato de potasio como sustrato en cultivo de pepino y jitomate

La agricultura es la base de la alimentación, se desarrolla en suelo e hidroponía. La hidroponía se explica cómo cultivos sin suelo, en soluciones nutritivas, para el caso del tomate y del pepino es en sustrato. Los sustratos han incrementado la productividad, con uso eficiente de agua y fertilizantes. Si la agricultura consume 70% de agua y en gasto 30% es fertilizantes, el objetivo de este trabajo fue utilizar hidrogel de acrilato de potasio por su capacidad de disminuir la pérdida de fertilizantes como ser reserva de agua, permitiendo mantener la producción de tomate y pepino. La investigación se realizó en Querétaro en 2017. Se evaluó diferentes capacidades de saturación del hidrogel para sus propiedades, la mezcla de sustrato y el rendimiento de tomate y pepino, encontrando diferencias significativas.

Reversible Functionalization of Clickable Polyacrylamide Gels with Protein and Graft Copolymers.

Modular strategies to fabricate gels with tailorable chemical functionalities are relevant to applications spanning from biomedicine to analytical chemistry. Here, the properties of clickable poly(acrylamide-co-propargyl acrylate) (pAPA) hydrogels are modified via sequential in-gel copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. Under optimized conditions, each in-gel CuAAC reaction proceeds with rate constants of ~0.003 s-1, ensuring uniform modifications for gels < 200 μm thick. Using the modular functionalization approach and a cleavable disulfide linker, pAPA gels were modified with benzophenone and acrylate groups. Benzophenone groups allow gel functionalization with unmodified proteins using photoactivation. Acrylate groups enabled copolymer grafting onto the gels. To release the functionalized unit, pAPA gels were treated with disulfide reducing agents, which triggered ~50 % release of immobilized protein and grafted copolymers. The molecular mass of grafted copolymers (~6.2 kDa) was estimated by monitoring the release process, expanding the tools available to characterize copolymers grafted onto hydrogels. Investigation of the efficiency of in-gel CuAAC reactions revealed limitations of the sequential modification approach, as well as guidelines to convert a pAPA gel with a single functional group into a gel with three distinct functionalities. Taken together, we see this modular framework to engineer multifunctional hydrogels as benefiting applications of hydrogels in drug delivery, tissue engineering, and separation science.

Desalination of Seawater Using Cationic Poly(acrylamide) Hydrogels and Mechanical Forces for Separation

AbstractIn this study, the ability of cationic poly(acrylamide‐co‐(3‐acrylamidopropyl)trimethylammonium chloride) hydrogels to desalinate seawater is explored, where the salt separation is based on the partial rejection of mobile salt ions by the fixed charges along the polymer backbone. Water absorbency measurements reveal that artificial seawater‐containing divalent ions (Mg2+, Ca2+, and SO42−) drastically decrease the swelling capacity of previously employed anionic poly(acrylic acid‐co‐sodium acrylate) hydrogels, whereas no influence on the swelling behavior of the synthesized cationic hydrogels is found. The swelling behavior and mechanical properties are studied by varying the degree of crosslinking and degree of ionization systematically in the range of 1–5 and 25–75 mol%, respectively. Finally, artificial seawater (csea = 0.171 mol L−1) is desalinated in a custom‐built press setup with an estimated efficiency of Em³ = 17.6 kWh m−³ by applying an external pressure on the swollen hydrogels.