Search

Both exogenous and endogenous reactive oxygen species (ROS) in vulvovaginal candidiasis (VVC) play pivotal roles in promoting the hyphal formation of Candida albicans (CA), which suggests that clearing ROS could inhibit CA hyphae formation. A ROS-sensitive hydrogel (CAS@4Arm-PB/CS) was formulated by using a novel four-arm polyethylene glycol (4Arm-PEG) derivative (4Arm-PB) as a crosslinking agent, chitosan (CS) as the hydrogel matrix, and caspofungin (CAS) as the antifungal drug against CA. The ROS-sensitivity, disintegration mechanism, crosslinking action, swelling degree, microstructure, modulus, and rheological properties of 4Arm-PB were characterized. According to the results, 5.0 % 4Arm-PB could quickly and efficiently cross-link 0.5 mg/mL of CS. The ROS-sensitivity of 4Arm-PB was 10-50 μM, indicating a strong ROS sensitivity. The in vitro and in vivo anti-CA results indicated that CAS@4Arm-PB/CS not only cleared endogenous and exogenous ROS and inhibited the formation of CA hyphae and biofilm but also contributed beneficially to the treatment of VVC mice caused by CA infection, implying a certain safety aspect and an in vivo applicability. This research introduces a novel functional crosslinking agent for CS hydrogel formulation, presenting a new avenue for hydrogel-based drug delivery systems and therapeutic strategies for VVC treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Introduction: Hyaluronan (HA)-based soft-tissue fillers are injectable crosslinked hydrogels aimed to counteract facial skin aging signs via minimally invasive procedures. The crosslinking step is required to drastically improve HA residence time in vivo and provide the gel with specific viscoelastic properties matching the clinical indications. While HA as a raw material and HA fillers are widely studied, little is reported about crosslinkers themselves used in commercial fillers., Areas Covered: This article introduces the specifications of the ideal crosslinker in HA fillers. The properties of commercially used crosslinkers are reviewed. An up-to-date review of innovative hydrogel fabrication alternatives is conducted, and advantages and drawbacks are discussed., Expert Opinion: HA fillers are predominantly manufactured using 1,4-butanediol diglycidyl ether (BDDE) which is considered as the gold standard crosslinker worldwide due to its proven and unrivaled clinical track record of more than 20 years. Extensive studies have been published covering BDDE-crosslinked HA fillers' chemistry, gel properties, and clinical effectiveness and safety. However, new hydrogel fabrication strategies have emerged, paving the way for innovative alternatives potentially bringing novel features to HA fillers. Nevertheless, major efforts must still be implemented to assess their safety, efficacy, stability and suitability for industrialization.

Photocrosslinkable gelatin hydrogels are excellent bioinks or biomaterial ink components to serve biofabrication applications. Especially the widely investigated gelatin-methacroyl (gel-MA) hydrogels hold an impressive track record. However, over the past decade, increasing attention is being paid to thiol-ene photo-click chemistry to obtain hydrogel networks benefitting from a faster reactivity (i.e. seconds vs minutes) along with superior biocompatibility and processability. In order to exploit this photo-click chemistry, often an ene-functionality (e.g. norbornene) is introduced onto gelatin followed by crosslinking in the presence of a multifunctional thiol (e.g. dithiothreitol). To date, very limited research has been performed on the influence of the applied thiolated crosslinker on the final hydrogel properties. Therefore, the present work assesses the influence of different thiolated crosslinkers on the crosslinking kinetics, mechanical properties and biological performance of the hydrogels upon encapsulation of primary adipose tissue-derived stem cells which indicated a cell viability exceeding 70%. Furthermore, the different formulations were processed using two-photon polymerization which indicated, in addition to differences in processing window and swelling ratio, a previously unreported phenomenon. At high intensities (i.e. ⩾150 mW), the laser results in cleavage of the gelatin backbone even in the absence of distinct photo-cleavable functionalities. This can have potential to introduce channels or softer regions in gels to result in zones characterized by different degradation speeds or the formation of blood vessels. Consequently, the present study can be used to provide guidance towards tailoring the thiol-ene system towards the desired applications., (Creative Commons Attribution license.)

Hydrogels, whose degradability can be controlled while also preserving cell viability or biomolecule stability, are in demand. Degradable polyethylene glycol crosslinkers are hydrolytically designed for use in hydrogels. Degradation is controlled by crosslinker chemical structure, such as introducing local hydrophobicity, steric hindrance, or electron-withdrawing moieties near a degradable ester moiety. Hydrogels made using these crosslinkers have gelation times from 1 to 22 min, storage moduli from 3 to 10 kPa, mesh sizes from 10 to 13 nm, and degradation times from 18 h to 16 d. However, when reaction conditions are modified to achieve similar gelation time, hydrogels have similar initial properties but preserve the wide range of degradation times. All crosslinkers support high cell viability upon hydrogel encapsulation or exposure to leachables and degradation products. This innovation in controlling degradation can help realize the hydrogels' potential for drug delivery or as matrices for cell encapsulation and transplantation., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Three dimensional (3D) bioplotting requires appropriate crosslinkers to crosslink the hydrogel precursor while simultaneously maintaining the viability of embedded cells. However, the evaluation and comparison of various types of crosslinkers in bioplotting remains underexplored to date. This paper presents our study of the influence of three ionic crosslinkers-calcium chloride (CaCl 2 ), barium chloride (BaCl 2 ), and zinc chloride (ZnCl 2 )-on the mechanical and biological properties of 3D bioplotted alginate scaffolds. The scaffold mechanical properties characterized included the elastic modulus, swelling, and degradation while the biological properties considered included Schwann cell viability and surface morphology. The mechanical and biological properties of the bioplotted scaffolds were both dependent on the crosslinkers used for fabrication; specifically, crosslinking ions resulted in the elastic modulus of the hydrogels decreasing in the order BaCl 2 >CaCl 2 >ZnCl 2 over 42 days while Schwann cell viability decreased in the order CaCl 2 >BaCl 2 >ZnCl 2 over 7 days. Taken together, these results offer insights that are effective in terms of manipulating the 3D bioplotting process so as to tune and optimize the mechanical and biological performance of the plotted scaffolds for tissue engineering applications.

Photo-crosslinking and self-healing have received considerable attention for the design of intelligent materials. A novel photostimulated, self-healing, and cytocompatible hydrogel system is reported. A coumarin methacrylate crosslinker is synthesized to modify the polyacrylamide-based hydrogels. With the [2+2] cyclo-addition of coumarin moieties, the hydrogels exhibit excellent self-healing capacity when they are exposed to light with wavelengths at 280 and 365 nm, respectively. To enhance cell compatibility, a poly (amidoamine) crosslinker is also synthesized. Variations in light exposure times and irradiation wavelengths are found to alter the self-healing property of the hydrogels. The hydrogels are shown to induce a regular cellular pattern. The hydrogels are used to regulate bone marrow stromal cells differentiation. The relative mRNA expressions are recorded to monitor the osteogenic differentiation of the cells., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This paper reports a simple technique to synthesize elasticity tunable hybrid hydrogels using photocleavable (N-hydroxysuccinimide terminated photocleavable tetra-arm poly(ethylene glycol); NHS-PC-4armPEG) and non-photocleavable (N-hydroxysuccinimide terminated tetra-arm poly(ethylene glycol); NHS-4armPEG) activated-ester type crosslinkers. Partially photodegradable hybrid hydrogels were synthesized by reacting the crosslinker mixture with amino-terminated tetra-arm poly(ethylene glycol) (amino-4armPEG). The photocleavable crosslinks are cleaved by irradiating light while the non-photocleavable crosslinks remain intact, resulting in decreased elasticity. We demonstrate that hydrogel elasticity can be controlled by adjusting the ratio of photocleavable NHS-PC-4armPEG and non-photocleavable NHS-4armPEG, and by varying the light exposure energy. We also show how micropatterned elasticity can be obtained in the hydrogels by irradiating with micropatterned light. These techniques could provide a novel platform to tailor the elasticity of hydrogels with microscale precision for biological studies in the near future., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Purpose: The goal of this study was to make pH-sensitive HPMC/Neocel C19-based interpenetrating polymeric networks (IPNs) that could be used to treat different diseases. An assembled novel carrier system was demonstrated in this study to achieve multiple functions such as drug protection and self-regulated release. Methods: Misoprostol (MPT) was incorporated as a model drug in hydroxyl-propyl-methylcellulose (HPMC)- and Neocel C19-based IPNs for controlled release. HPMC- and Neocel C19-based IPNs were fabricated through an aqueous polymerization method by utilizing the polymers HPMC and Neocel C19, the initiator ammonium peroxodisulfate (APS), the crosslinker methylenebisacrylamide (MBA), and the monomer methacrylic acid (MAA). An IPN based on these materials was created using an aqueous polymerization technique. Samples of IPN were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermal analysis (TGA), and powder X-ray diffraction (PXRD). The effects of the pH levels 1.2 and 7.4 on these polymeric networks were also studied in vitro and through swelling experiments. We also performed in vivo studies on rabbits using commercial tablets and hydrogels. Results: The thermal stability measured using TGA and DSC for the revised formulation was higher than that of the individual components. Crystallinity was low and amorphousness was high in the polymeric networks, as revealed using powder X-ray diffraction (PXRD). The results from the SEM analysis demonstrated that the surface of the polymeric networks is uneven and porous. Better swelling and in vitro results were achieved at a high pH (7.4), which endorses the pH-responsive characteristics of IPN. Drug release was also increased in 7.4 pH (80% in hours). The pharmacokinetic properties of the drugs showed improvement in our work with hydrogel. The tablet MRT was 13.17 h, which was decreased in the hydrogels, and its AUC was increased from 314.41 ng h/mL to 400.50 ng h/mL in hydrogels. The blood compatibility of the IPN hydrogel was measured using different weights (100 mg, 200 mg, 400 mg, and 600 mg; 5.34%, 12.51%, 20.23%, and 29.37%, respectively). Conclusions: As a result, IPN composed of HPMC and Neocel C19 was successfully synthesized, and it is now possible to use it for the controlled release of MPT. [ABSTRACT FROM AUTHOR]

It has become crucial to develop new adsorbents to remove toxic dye wastes from wastewater to protect our existing aquatic ecosystem. Here, to remove methyl orange azo dye from aqueous solutions, a new p(HEMA-co-AETAC)/VMt nanocomposite hydrogel was prepared by using 2-hydroxyethyl methacrylate and [2-(acryloyloxy)ethyl]trimethylammonium chloride monomers using vinyl-based montmorillonite crosslinker. Obtained new types of crosslinker and nanocomposite hydrogels have been characterized by various analysis methods. In addition, the effects of crosslinker amount, monomer amount and pH on the swelling behavior of nanocomposite hydrogel were investigated. The effects of essential parameters such as contact time, initial dye concentration, pH effect of the solution, adsorbent amount, and temperature on adsorption were evaluated. It was determined that there was no significant change in the adsorption ability of the nanocomposite hydrogel in the pH range of 3–10. Experimental results showed that the Langmuir isotherm model fit better, and the calculated maximum adsorption capacity was 961.54 mg/g. In addition, it was determined that vinyl-based montmorillonite used as a crosslinker supported MO adsorption. p(HEMA-co-AETAC)/VMt nanocomposite hydrogel may be a new type of adsorbent to remove toxic synthetic dye residues from aqueous media. A new adsorbent for the removal of toxic synthetic dye residues from aqueous media in a wide range of pH. Hydrogels containing AETAC and HEMA are easily obtained with modified montmorillonite. The adsorption properties of the nanocomposite hydrogel were evaluated with methyl orange dye molecules. According to Langmuir isotherm, the maximum adsorption capacity was determined to be 961.54 mg/g. [ABSTRACT FROM AUTHOR]

Poly(N-isopropylacrylamide) (P(NIPAAm)) hydrogels were prepared by free-radical polymerization with biodegradable poly (β-amino ester) (PBAE) crosslinkers at 1 wt% and 3 wt% ratio, and compared with conventional N,N′-methylene bisacrylamide (MBA)-crosslinked hydrogel. The influence of the type, molecular weight, and diacrylate/amine ratio of the crosslinker on the crosslink density, compressive strength, and swelling and biodegradation behavior of the hydrogels was investigated. The hydrogels synthesized with lower molecular weight PBAE crosslinkers showed higher crosslinking degrees and compressive strength and lower swelling ratios. To reveal the controlled release behavior of the fertilizer, KNO3 was used as the model, and its loading and release behavior from these hydrogels was also examined. The N/T5/1 sample with 1.5/1.0 diacrylate/amine molar ratio and 1 wt% PBAE ratio demonstrated the most controlled release of KNO3 with 66.9% after 18 days in soil. In addition, the hydrogel with the porosity of 71.65% and crosslinking degree of 2.85 × 10−5 mol cm−3 showed a swelling ratio of 69.44 g/g, biodegradation rate of 23.9%, and compressive strength of 1.074 MPa. Thus, it can be concluded that the new designed biodegradable P(NIPAAm) hydrogels can be promising materials as nitrate fertilizer reservoirs and also for controlled fertilizer release in soil media for agricultural applications. [ABSTRACT FROM AUTHOR]

Purpose: The goal of this study was to make pH-sensitive HPMC/Neocel C19-based interpenetrating polymeric networks (IPNs) that could be used to treat different diseases. An assembled novel carrier system was demonstrated in this study to achieve multiple functions such as drug protection and self-regulated release. Methods: Misoprostol (MPT) was incorporated as a model drug in hydroxyl-propyl-methylcellulose (HPMC)- and Neocel C19-based IPNs for controlled release. HPMC- and Neocel C19-based IPNs were fabricated through an aqueous polymerization method by utilizing the polymers HPMC and Neocel C19, the initiator ammonium peroxodisulfate (APS), the crosslinker methylenebisacrylamide (MBA), and the monomer methacrylic acid (MAA). An IPN based on these materials was created using an aqueous polymerization technique. Samples of IPN were analyzed using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry (DSC), thermal analysis (TGA), and powder X-ray diffraction (PXRD). The effects of the pH levels 1.2 and 7.4 on these polymeric networks were also studied in vitro and through swelling experiments. We also performed in vivo studies on rabbits using commercial tablets and hydrogels. Results: The thermal stability measured using TGA and DSC for the revised formulation was higher than that of the individual components. Crystallinity was low and amorphousness was high in the polymeric networks, as revealed using powder X-ray diffraction (PXRD). The results from the SEM analysis demonstrated that the surface of the polymeric networks is uneven and porous. Better swelling and in vitro results were achieved at a high pH (7.4), which endorses the pH-responsive characteristics of IPN. Drug release was also increased in 7.4 pH (80% in hours). The pharmacokinetic properties of the drugs showed improvement in our work with hydrogel. The tablet MRT was 13.17 h, which was decreased in the hydrogels, and its AUC was increased from 314.41 ng h/mL to 400.50 ng h/mL in hydrogels. The blood compatibility of the IPN hydrogel was measured using different weights (100 mg, 200 mg, 400 mg, and 600 mg; 5.34%, 12.51%, 20.23%, and 29.37%, respectively). Conclusions: As a result, IPN composed of HPMC and Neocel C19 was successfully synthesized, and it is now possible to use it for the controlled release of MPT.

The aim of this study was to evaluate the persistence of alkaline hydrogels based on a common (N,N′-methylenebisacrylamide, BIS) and three recently published tetraallyl crosslinkers. Such hydrogels have been shown to be suitable materials for the rehabilitation of cementitious materials. Of the four crosslinkers under investigation, N,N,N′,N′-tetraallylpiperazinium dibromide decomposed quickly in 1 m KOH solution and was not considered further. BIS showed the first signs of a decomposition after several days, while tetraallylammonium bromide and N,N,N′,N′-tetraallyltrimethylene dipiperidine dibromide remained unaffected. In contrast to BIS, which suffers from low solubility in water, the two tetraallyl crosslinkers show unlimited miscibility with diallyldimethylammonium hydroxide solutions. For the study, gels with up to 50 wt % crosslinker were prepared. Of these, gels containing tetraallylammonium bromide always show the highest degrees of swelling, with a peak value of 397 g/g at a content of 2 wt %. Under accelerated ageing at 60 °C for 28 d, gels crosslinked with BIS ultimately turned liquid, while the storage modulus and the degree of swelling of the two tetraallyl-crosslinked gels remained unchanged. This indicates that alkaline gels can be suitable for long application periods, which are common for rehabilitation measures in the construction industry. [ABSTRACT FROM AUTHOR]

Polymer-dispersed liquid crystal (PDLC) is a striking material that has a great role in optoelectronic display devices. In this paper, PDLC films were prepared by the polymerisation-induced phase separation (PIPS) process under the same curing temperature, UV intensity, and photo-initiator dosage. The morphology and electro-optical properties of PDLC with crosslinker content, the liquid crystal content, and magnetic nanomaterial doping were comprehensively investigated. Different crosslinker and liquid crystal contents changed the crosslinker degree and free radical content in the blends, which changed the polymer network size while changing the electro-optical properties of PDLC. The magnetic nanomaterials dispersed in PDLC established the intrinsic potential and reduced the threshold voltage (24.1 V) and saturation voltage (54.5 V) were obtained at a Fe3O4 NPs doping concentration of 1.0 wt%, which led to a CR of 89.9 and a toff of 14.1 ms. This work provides a feasible method to optimise the electro-optical properties of PDLC and provides the possibility for the wide application of PDLC. [ABSTRACT FROM AUTHOR]

There is a myriad of ways to crosslink hydrogel wound dressings; however, they require additional steps to remove the residue of the crosslinking agents, or their byproducts in biological environments are toxic. In this study, we studied and characterized the crosslinking of the chitosan hydrogels by various dicarboxylic acids, including oxalic acid, adipic acid, and sebacic acid under vacuum at 90 °C. The concentrations of the crosslinkers in the crosslinked hydrogels are tolerable for the cells, and the membranes can be used after crosslinking without complicated additional steps to remove the unreacted residues. The molar ratio of the crosslinkers was calculated based on the stoichiometry of the chitosan amine groups. Attenuated total reflectance Fourier transform infrared spectroscopy revealed amide linkage formation between amine groups of the chitosan and carboxyl groups of the dicarboxylic acids at 90 °C. The results showed that the chitosan membranes crosslinked with oxalic acid had higher Young's modulus (~ 1042 N/mm2) and ultimate tensile strength (~ 75 N/mm2) in comparison with the other dicarboxylic acids. Moreover, the membranes crosslinked with oxalic acid showed a weight loss of ~ 5.4% after 24 h at double-distilled water, which was drastically lower than that of the others. Thus, oxalic acid was selected as the most effective crosslinker. Cell viability assay, using mouse fibroblast (L929) cells, was conducted on the mechanically optimized membranes. The fibroblast cells successfully attached and spread well on the surface of the membranes. In conclusion, the obtained results suggested oxalic acid as an effective and non-toxic crosslinker for chitosan-based membranes for wound dressing applications. [ABSTRACT FROM AUTHOR]

In this work, the synthesis of crosslinked chitosan hydrogels was performed by ionic and covalent interactions using tripolyphosphate (TPP) and formaldehyde (CH 2 O), respectively. The hydrogels synthesis was performed using a D-Optimal combined experiment design with two mixing variables, A and B representing the TPP weight fraction (slack variable) and CH 2 O weight fraction, respectively, and three (3) process variables C-chitosan concentration, D-cross-linker concentration, and E-Contact time. The response variables studied were the point of zero charge (pH PZC), the swelling ratio (SW), and the equilibrium water content (EWC), which are relevant physicochemical properties in applications such as the pollutant removal from water. According to the ANOVA results, the model obtained was significant; this means it can be adequately used to predicting pH PZC , SW, and EWC from the mixing and process variables, obtaining coefficients of determination R2 of 0.9572, 0.8900, and 0.8447, respectively. The pH PZC is affected by chitosan concentration, while the crosslinker concentration influences the SW, and the contact time most significantly affected the EWC. Morphology and hardness tests, thermal stability, infrared spectroscopy, and scanning electron microscopy, allowed verifying the types of crosslinking of chitosan with TPP and CH 2 O. [ABSTRACT FROM AUTHOR]

The toxicity level of conventional hydrogels is considerably high for most applications. To date, very few studies on hydrogels synthesized using only safe materials and simple, reproducible processes are available in the literature. Moreover, critical information on hydrogels hydrolytic behavior and stability—important parameters to determine microstructure—is missing. Herein, new composite hydrogel matrices are developed using green, sustainable materials through a simple, reproducible low-temperature chemical method. Natural polymers (carboxymethyl cellulose and chitosan), crosslinkers (fumaric acid, citric acid, tartaric acid and zinc ion), and solvent (water) are used. The hydrogels are characterized for degree of crosslinking and microstructure parameters calculated using Flory Rehner equation. Bonding strength and stability of the microstructure are further assessed. With respect to the hydrolytic properties, it was found that CMC~FU~CSN exhibits well-defined microstructure (155% swelling, 79% water absorbency and 82% gel fraction) superior to the other crosslinked hydrogels and the non-crosslinked composite, CMC~CSN. However, its gel fraction was within the same range as CMC~CSN (332% swelling, 91% water absorbency and 79% gel fraction). Other characterization results confirm that CMC~FU~CSN has the optimum microstructure (3 nm mesh size, 261 g/mol molecular weight between crosslinks and 0.01 μmol/cm3 effective crosslinking density), thermal stability (2% mass loss at 50 °C, 3% at 100 °C against 6% at 50 °C, 8% at 100 °C for CMC~CSN), semi-crystalline structure and chemical properties making it preferred over CMC~CSN as a promising green and sustainable hydrogel matrix. [ABSTRACT FROM AUTHOR]

Hydrogels are hydrophilic macromolecular systems that swell in water without dissolving. The nature of the solvent has a significant effect on the amount of water absorbed. Poly(acrylamide) hydrogel and its copolymer with diprotic maleic acid are prepared in this work by copolymerization and chemical crosslinking with methylene bisacrylamide; at different mass percentages of acrylamide (AAm, %) and maleic acid (MA, %), respectively: (100, 0%) and (80, 20%). The obtained results show the formation of copolymers with intermolecular hydrogen bonding between carboxylic groups and amide groups. The content of maleic acid within the crosslinked polymer (acid value) is determined. Two acid values are obtained; 14 and 57.2 mg g–1. Thermal stability of hydrogels is examined through TGA analysis. The thermal degradation of poly(acrylamide) occurs via two stage process; (204–330°C) and at temperature higher than 330°C. The thermal stability of the copolymer increases with incorporates of MA. The copolymer degrades in a multistage process; less than 230°C, (230–350°C) and above 350°C. Different percentages of crosslinker between 1–5 wt % and copolymer with maleic acid are used to study their swelling behavior in different aqueous solutions (NaCl, pH 9.18 and pH 2.2). The swelling is reduced with increasing degree of the cross-linking agent. The obtained hydrogels have shown substantial percent swelling in water and basic buffer and shrinking in saline solution and acidic buffer. The results show that MA20 hydrogel has pH and ionic sensitive characters. These sensitivities exhibit hydrogels an important utility in water treatments, especially as adsorbent of heavy metal ions. The study of oscillatory swelling of hydrogels at pH 4.01 and 9.18 as function of time are demonstrated in this work. The result shows that the synthesized hydrogels exhibit excellent reversible pH-sensibility character. [ABSTRACT FROM AUTHOR]

Crosslinked chitosan (CS) is one of the most useable hydrogels in biomedicine and tissue engineering. Unlike most chitosan crosslinkers that are toxic, such as glutaraldehyde, vanillin is a natural, biocompatible, and antimicrobial alternative. The crosslinking of chitosan and vanillin consists of Schiff base bonds between the amines of chitosan and the aldehydes of vanillin, in addition to hydrogen bonds formed across the network. In most studies, the combination of chitosan and vanillin has been investigated in small sizes (micro/nanoscale and biofilms). In this study, a chitosan-vanillin (CV) hydrogel was studied on a macroscale with a three-dimensional porous structure, and it was compared with chitosan crosslinked with glutaraldehyde (CG) on the same scale. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (FE-SEM) used to identify the bonds formed and examine the morphology of the hydrogels. The gel content, swelling, porosity, mechanical properties, cell viability (on L929 and mesenchymal cells), and antibacterial activity (against Escherichia coli and Staphylococcus aureus) of the samples were investigated. The results showed that the CV had both gel content and high porosity (>90%), with an interconnected porous network of uniform pore size. The CV hydrogel exhibited good antibacterial activity and cell viability. In terms of mechanical properties, CV has weaker mechanical properties compared to CG in the dry state, while the mechanical properties of CV have more improved in the swollen state compared to CG. [ABSTRACT FROM AUTHOR]

Hydrogel treatment is one of the most important chemical methods to reduce excessive water in mature reservoirs. In this study, four hydrogel systems were studied for applying in water shutoff treatments. The hydrogel systems consisted of sulfonated polyacrylamide and chromium triacetate, aluminum nitrate nonahydrate (both as inorganic crosslinkers), polyethyleneimine, and hexamethylenetetramine (both as organic crosslinkers). The effects of polymer and crosslinker concentrations and their interactions on gelation and syneresis times were determined using the central composite design method. Based on the results values, four investigated samples of the hydrogel systems were selected for further rheological and thermal stability investigations. Among the four selected hydrogels, the polyethyleneimine one retained its structure under strains below 2050%. Thus, this system was recommended to use under different reservoir conditions (up to 110 °C). Moreover, it was found that gelation time and gel strength could be controlled by both adjusting polymer and crosslinker concentrations and choosing the right crosslinker type. The results of the study might be used in selecting the proper type of crosslinker in hydrogels based on their gelation time, syneresis time, deformation strength, and thermal stability for specific operating conditions. [ABSTRACT FROM AUTHOR]

Inhomogeneities are responsible for the poor mechanical properties of hydrogels. To achieve good performances, this study reports here the design and synthesis of hydrogels with negligible defects named as initiator-crosslinker (IC) hydrogel where hybranched polyether amine (hPEA) performs as both coinitiator and crosslinker. The initiation mechanism used in this system is classical but the crosslinking mechanism is different from the conventional hydrogels. A series of hydrogels with various mechanical properties are synthesized by varying the content ratio of coinitiator hPEA and initiator ammonium persulfate. Tensile tests demonstrated that IC hydrogels had excellent mechanical properties elongation at break up to 3000%. The toughness calculated from stress-strain curve highly depended on the content of hPEA and the largest one is about 4.02 MJ m−3 which is much higher than the conventional hydrogels (0.03 MJ m−3). Rheological and swelling results also indicated the obtained hydrogels are indeed crosslinked by both chemical bond and physical interaction. [ABSTRACT FROM AUTHOR]

Multifunctional and multiresponsive hydrogels demonstrate excellent promise for multifarious applications but often suffer from high synthesis complexity and poor resource availability. Herein, based on the boronate-catechol interactions between a disulfide-containing, boronic acid-based crosslinker, and a catechol-functionalized poly( N-isopropyl acrylamide), a multitasking hydrogel with double dynamic network is developed. By integrating the inherent heat-responsive property of poly( N-isopropyl acrylamide) and bioadhesion of catechol moieties with the reversibility and dynamic features of boronate ester and disulfide bonds, the final hydrogel is endowed with not only temperature, pH, glucose, and redox quadruple-stimuli sensitiveness, but also autonomic self-healing property and biomimetic adhesion ability. Moreover, the rheological and adhesive properties can be readily tuned by adjusting the amount of crosslinker or the catechol in polymer precursor. Considering the readily prepared starting materials, easy preparation, high flexibility in tuning hydrogel properties, the procedure provided here opens up a promising avenue to develop multifunctional hydrogels for multifarious applications. [ABSTRACT FROM AUTHOR]

The polymerization was carried out under the different concentrations of acrylamide and crosslinker in an aqueous solution of NO2 gas as initiator at 50°C. The resulting polyacrylamide was saponified with NaOH solution. The hydrolysed polymers show high degree of water swelling (>500) than that of unhydrolysed polymers (<100). Swellability of the gel decreases with the increasing concentration of N, N'- methylene bisacrylamide − a crosslinker which enhances the degree of crosslinking in the polymer chains. The increased crosslinking restricts the expansion of polymer network which causes the lowering of the water absorbency. It was observed that polymer hydration increased with the molar mass of polyacrylamide. The swellability of polyacrylamide hydrogels is greatly lowered by the addition of ionic salts in the swelling medium. Both ionic strength and valency of the salts are responsible to decrease the water uptaking capacity of the gels which remain unaffected by nondessociating nature of urea. The hydrogels, so prepared, are stable and quite able to undergo swelling − deswelling cycles suggesting their reversible characters. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanical and adhesive properties of P (THAM/AM) hydrogel are tailored by CNF. • Compared with MBA, using CNF leads to high mechanical strength of hydrogels. • Compared with MBA, using CNF results in reduced adhesion loss of hydrogels. • P (THAM/AM)-CNF-Fe3+ strain sensor shows high sensitivity and long-term stability. • P (THAM/AM)-CNF-Fe3+ sensor shows superior sensing ability for motion detection. Conductive hydrogels are regarded as one of the promising synthetic materials for emerging applications such as soft robotics, bioelectronics, and wearable devices. Herein, poly (N- [tris (hydroxymethyl) methyl] acrylamide- co -acrylamide) (P (THAM/AM)) adhesive hydrogels were tailored by physically cross-linking with cellulose nanofiber (CNF). Compared with chemical crosslinker (N,N'-methylene bisacrylamide), CNF complexing with multiple hydroxyl groups on P (THAM/AM) chains led to the formation of numerous hydrogen bonds, endowing the hydrogel with additional energy dissipation and resulting in a better strength reinforcement for adhesive hydrogels. Furthermore, we introduced ferric ions (Fe3+) into the hydrogel to make the hydrogel conductive for producing a strain sensor with desired adhesion, high sensitivity, fast response time, and superior durability. The fabricated hydrogel strain sensor attached well to human skin and was able to translate both large and subtle human motions into relative resistance changes, showing its promising applications in wearable electronics for human motion detection. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new method to process high viscous, viscoelastic and crosslinked biopolymers. • A new method to remove crosslinking agent and byproduct from high viscous biopolymers. • Dynamic crossflow filtration (DCF), a fast, effective and economical method. • DCF has no negative impact on rheological characteristics of the vicoelastic fluid. • Removal of 99% of residual chemical agents by applying 7 diafiltration volumes. The current study shows a new possibility to purify crosslinked hydrogels based on hyaluronic acid (HA) to remove the residual crosslinking agent 1,4 - butanediol diglycidyl ether (BDDE) and its byproduct 1,4-butanediol di-(propan-2,3-diolyl) ether (EPD) using a crossflow filtration (CFF) device. Therefore, a dynamic crossflow-filtration (DCF) device with rotating and semipermeable ceramic filter discs (5 nm, 60 nm, 2000 nm) was used. No negative impacts on the thermal stability and rheological characteristics of the biopolymer could be shown. Furthermore, it was discovered, that 7 diafiltration volumes (DV) are sufficient to reduce the residual contaminants to < 0.1 % from the initial concentration and that the hyaluronic acid (HA) rejection coefficient (R) is 0.99 regardless of the chosen membrane pore size, while the permeability of BDDE and EPD remains at almost 100 %. No correlation between the membrane pore size and the flux could be found. For all membranes, the flux is surprisingly dropping after 0.5 DV was processed, which could be linked to the HA swelling and membrane pore blocking effects. The highest flux was determined for the 60 nm membrane with 32 Lm-2h−1 at steady state. The stability of the biopolymer is neither negatively influenced by the applied shear forces due to the rotational membrane velocity, nor by the applied thermal stress conditions for 6 months at 25 °C, 60 % relative humidity (r.h.) and 40 °C, 75 % r.h. The presented results show that a dynamic diafiltration can be regarded as a promising alternative to conventional purification methods. [ABSTRACT FROM AUTHOR]

In the present study, superabsorbents (SAPs) of cationic monomer [2-(methacryloyloxy) ethyl] trimethylammonium chloride have been prepared by free radical solution polymerization with different crosslinkers. They were subjected to repeated cycles of swelling and de-swelling in deionized water and NaCl solution. The conductivity of the swelling medium was measured and related to the swelling/de-swelling characteristics of the SAPs. The swelling capacity was also determined in saline solution. The swelling and de-swelling processes were described by first-order kinetics. The SAPs exhibited varied swelling capacity for crosslinkers of the same functionality as well as different functionality. The SAPs were used to adsorb the dye Orange G at different initial concentrations of the dye. The equilibrium adsorption data followed the Langmuir adsorption isotherms. The SAPs were also used to adsorb three other dyes, namely, Congo red, Amido black and Alizarin cyanine green. They exhibited different adsorption capacities for different dyes. The adsorption phenomenon was found to follow first-order kinetics. [ABSTRACT FROM AUTHOR]

A novel approach is presented for the synthesis of thermoresponsive and pH-sensitive magnetic nanohydrogels by using the biodegradable starch-maleate as a crosslinker and magnetic nanoparticles stabilizer. Chemically modified starch-maleate produces highly stable Fe3O4magnetic nanopaticles (MNPs) aqueous dispersion. Then,N-isopropylacrylamide (NIPAAm) and itaconic acid (IA) are successfully polymerized from the vinyl double bonds of the starch-maleate-MNPs to prepare the thermo- and pH-responsive magnetic nanohydrogels. The obtained PNIPAAm-g-(starch-MNPs) and (PNIPAAm-co-IA)-g-(starch-MNPs) nanohydrogels are characterized by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectrometer, X-ray diffraction, differential scanning calorimetry, thermal gravimetric analysis, and vibrating sample magnetometer. Also, pH- and temperature-responsive behaviors of the synthesized magnetic nanohydrogels are investigated and, finally, the cytotoxicity and drug loading are examined with mitoxantrone (MTX) as an anticancer drug model. The results confirm the low toxicity and enhanced anticancer effect of MTX-loaded magnetic nanohydrogels. [ABSTRACT FROM AUTHOR]

A series of multicomponent hydrogels were prepared by the copolymerization of hydrophobic silicon-containing monomer 3-bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate (SiMA) with the solvent-responsive monomers 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (NVP) and thermosensitive monomer N, N-dimethyl acrylamide (DMA). 2-Hydroxy-2-methyl phenyl acetone (D-1173) was chosen as UV initiator and five different dienes/triene monomers were selected as crosslinking agent in order to select the best crosslinker. The ethanol extraction experiments as well as the FTIR, DSC and TG results showed that the copolymerization was effective. The optical, permeability, and mechanical analysis results demonstrated that the obtained hydrogels were highly transparent with good oxygen permeability and mechanical properties. And the impact of crosslinker on the mechanical properties of the hydrogels was also discussed in detail. The basic results demonstrated that the obtained hydrogels had good stimuli-responsive effects to both pH value and solvent. [ABSTRACT FROM AUTHOR]

We have developed a novel hydrogel that is formed from a crosslinkable trilayered polymeric micelle and a polyamine for the sustained release of hydrophilic compounds. This hydrogel is quite unique because the vesicle-like structure of the trilayered polymeric micelle acts as not only a crosslinker of the hydrogel but also a container of hydrophilic compounds. The hydrogel is rapidly formed by mixing both the trilayered polymeric micelle solution and the polyamine solution. The gelation property of the hydrogel, such as the storage modulus, can be changed by tuning the molecular weights, concentrations, and pH of the dissolving solvent of the hydrogel's constituent components. Furthermore, it is clarified that the structural difference among the micelles acting as crosslinkers affects the gelation property of the hydrogel. Amazingly, the hydrogel that is formed from the trilayered polymeric micelles possessing a vesicle-like flexible structure exhibits a higher storage modulus than the hydrogel that is formed from the bilayered polymeric micelles possessing a highly packed, hard structure. Our results demonstrates that a microscopic structural difference of crosslinkers can induce a macroscopic (and, in some cases, an interesting and unexpected) change in the properties of the resulting hydrogels. For medical applications, the hydrogel proposed in the present article can encapsulate the hydrophilic compounds so that the hydrogel can be available as the material for their sustained release. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 [ABSTRACT FROM AUTHOR]

The use of polymers in human healthcard has revolutionized the development of smart material with beneficial features for biomedical applications. A large number of natural and synthetic polymers are available for this purpose. In this respect chitosan (CS) has gained much research interest. The present study reports the physiochemical properties of crosslinked CS and polyethylene glycol (PEG) blend system. Sodium trimetaphosphate, glyoxal and boric acid were used as crosslinkers. The crosslinked CS-PEG blended films were characterized by X-ray diffraction,rigidity measurement and swelling studies. Swelling studies was observed to be influenced by the proportion of crosslinkers, crosslinking time, temperature and the pH of the solution. This study furnishes that STMP is a non toxic and efficient crosslinker for CS-PEG blend system. It may be expected to be potential candidate for biomedical applications and human healthcare systems [ABSTRACT FROM AUTHOR]

In this work, hydrogels were prepared from carboxymethyl cellulose (CMC) and 1-vinyl-2-pyrrolidone (VP) by Electron Beam irradiation in the presence of N,N'-methylenebisacrylamide (BIS) as a crosslinking agent. The parameters studied include stirring time and percentage ofcrosslinking agent. Hydrogels were characterized using Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). VP and BIS were found be effective as reinforcement materials to improve the properties of CMC. Meanwhile, the optimum conditions were 5% BIS and 3 hours of stirring time. The gel fraction increased when irradiation dose was increased. FTIR confirmed the crosslinking reaction between CMC and VP after the irradiation process by using BIS as the crosslinking agent. TGA thermograms showed changes in the thermal properties of CMC-VP hydrogels in the presence of different amounts of BIS. [ABSTRACT FROM AUTHOR]

Recent advances in drug delivery have been directed towards the design of a number of intelligent systems for the treatment of various diseases. In this regard, we developed novel surfactant-modified hydrogels which are synthesized from acrylamide (AM) and acrylamido propane sulphonic acid (AMPS), in the presence of a surfactant (Latemul PD-104) using ammonium persulfate/N,N,N',N'-tetramethylethylene diamine (APS)/(TMEDA) as an initiating system and N,N'-methylenebisacrlyamide (MBA) as a crosslinker. The hydrogel formation was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The variation in the hydrogel networks formation employing different levels of synthetic parameters was verified by swelling studies. Influences of salt, biological fluids, and buffer solutions on the developed systems were also investigated. It was found that, compared to PAM hydrogel, all the surfactant-modified hydrogels were responsive towards salt concentration and pH. A robust drug release behavior was observed from surfactant-modified hydrogel systems. [ABSTRACT FROM AUTHOR]

Abstract: Drying experiments of polyacrylamide (PAAm) gels were performed using steady-state fluorescence (SSF) spectrometer. Pyranine (P) was introduced as a fluorescence probe and intensity of P from various cross-linker content gel samples was monitored. It was observed that the intensity of P increased during the in situ drying processes. Gravimetrical and volumetric experiments were also performed. An empirical model was derived and introduced to determine the desorption coefficient, D of water molecules from the drying PAAm gels. It is observed that D increased as the cross-linker content was increased. [Copyright &y& Elsevier]

[Display omitted] • Laminar GO membranes were fabricated using triethanolamine (TEOA) as crosslinker. • TEOA crosslinker effectively suppressed swelling of the GO laminar structure. • Affinity between TEOA and solvents was estimated using Hansen solubility parameters. • Affinity was important factor in controlling interlayer spacing and solvent permeation. Two-dimensional (2D) laminar membranes are attracting much attention in organic solvent nanofiltration owing to the promising permeation and selective performance derived from their 2D ultrathin separation layer. However, owing to easy swelling (enlargement of interlayer spacing), controlling the interlayer spacing in organic solvents and stable solvent permeation are major issues for their application to organic solvent systems. In this study, laminar GO membranes were fabricated on a porous polyketone (PK) support membrane using triethanolamine (TEOA) as crosslinker (GO-TEOA/PK). The interlayer spacing (d) between GO sheets was characterized by X-ray diffraction. The TEOA crosslinker effectively suppressed swelling of the GO laminar structure. For GO-TEOA/PK, the variation in d corresponded well with the affinity between TEOA and each solvent, R a (TEOA–solvent), as estimated using the Hansen solubility parameters. Furthermore, common linear correlation between the permeance of alcohols and the parameter combining affinity, viscosity, and equivalent molar diameter was clearly observed. Therefore, the affinity between crosslinker and solvent was an important factor in controlling interlayer spacing and solvent permeation in the laminar GO membranes containing crosslinker. [ABSTRACT FROM AUTHOR]

Polymeric hydrogels based on biocompatible materials, methacrylic acid (MAA), were designed and synthesized. Synthesis was carried out by free-radical copolymerization using potassium persulfate as initiator and N,N′-methylenebisacrylamide as crosslinker. Hydrogels were also characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR) and differential scanning calorimetry (DSC). DSC was used for the quantitive determination of the amounts of freezing and non-freezing water of the hydrogels with 0.5% of N,N′-methylenebisacrylamide. Equilibrium swelling of hydrogels was studied in phosphate buffer of physiological pH (1.0, 4.0, 7.4 and 8.5) at 37 °C. The swelling kinetic of the hydrogels were studied and the kinetic characteristic constant of copolymeric systems, k, and the exponent which characterizes the mechanism of water transport at short times, n, were obtained. Metoclopramide hydrochloride was entrapped into the hydrogels by sorption and the “in vitro” release profile of this drug was established in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). It was observed that the drug release mechanism was non-Fickian. [Copyright &y& Elsevier]

Fast-swelling highly porous superabsorbent hydrogels were synthesized through a rapid solution polymerization of concentrated partially neutralized acrylic acid under normal atmospheric conditions. Acetone and sodium bicarbonate were used as porosity generators (porogens) during polymerization process for porosity generation. N,N′-methylenebisacrylamide (MBA) and 1,4-butanedioldiacrylate were used as the water- and the oil-soluble crosslinkers, respectively. The temperature changing of the reaction mixture during polymerization and foam formation process was monitored and investigated in details. Time and sequence of addition of the porogens and gelation time were recognized to be important to increase efficiency of the porogens. The concentration of the crosslinkers on gelation time was optimized to achieve highly porous products. It was found that higher crosslinker concentration, especially in the case of MBA, causes decreased gelation times. Shorter gelation time resulted in more porogen bubbles trapped in the viscose reaction mixture led to products with higher porosity. The effect of type and concentration of the crosslinking agents on the process and swelling behavior of the hydrogels (in water and saline solutions) were investigated. Power law relationships were found for the variation of swelling in terms of either crosslinker or saline concentration. Less sensitivity to the change of salinity was achieved by employing higher amount of crosslinker. [Copyright &y& Elsevier]

[Display omitted] • Bisphosphonate-functionalized poly(amido amine) macromer (PAA-BP) was synthesized. • Crosslinking with PAA-BP adds excellent mineralization ability to 2-hydroxyethyl methacrylate (HEMA) hydrogel. • This hydrogel is biocompatible and facilitates cell adhesion after mineralization. • PAA-BP improves swelling and degradation properties of the hydrogel. • This hydrogel can be used for tissue engineering scaffolds. The first water soluble, bisphosphonate (BP, not bisphosphonic acid)-functionalized poly(amido amine) macromer (PAA-BP) is synthesized and used as a crosslinker for synthesis of a biodegradable and biocompatible hydrogel for tissue engineering scaffolds. The synthesis of PAA-BP is performed in three steps, the first two giving the control macromers (PAA-NHBoc and PAA-NH 2): i) Michael addition reaction of N,N' -methylene bisacrylamide and N -Boc-1,6-hexanediamine (acrylamide/amine ratios of 1.2), ii) deprotection of Boc-protected amine groups, iii) Michael addition reaction of the amine groups with tetraethyl vinylidene bisphosphonate. The degree of BP substitution is 50% and molecular weight of the PAA-BP macromer is found to be 4800 g/mol. These macromers are incorporated into hydrogels by copolymerization with 2-hydroxyethyl methacrylate and the influence of bisphosphonate functionality on hydrogel properties; degradation, swelling, mechanical and mineralization, is investigated. The mineralization abilities, hence the mechanical properties of the hydrogels are strongly influenced by the BP functionality; PAA-BP forming strong (E = 83 ± 1 kPa) hydrogel-apatite composites, PAA-NH 2 also working to a lesser degree (E = 54 ± 3 kPa). Cytocompatibility of the hydrogels is observed on Saos-2 human osteosarcoma, U-2 OS human bone osteosarcoma epithelial, C2C12 mouse myoblast muscle and NIH mouse embryonic fibroblast 3T3 cells. PAA-BP crosslinked hydrogels facilitate adhesion of C2C12 cells after mineralization. In summary, BP-functionalized hydrogel may have a potential impact on bone tissue engineering. [ABSTRACT FROM AUTHOR]

In this work, a hydrogel system was produced via radical polymerization of N,N-dimethylacrylamide and 2-acrylamido-2-methylpropanesulfonic acid in the presence of N,N-methylene-bis-acrylamide as a crosslinker and ammonium persulfate as an initiator. Parameters that impact the conversion of copolymerization (such as initial concentration of monomers, temperature, initiator dose, and time) were studied. The swelling degree of the hydrogel was investigated with the addition of a crosslinker and initiator at different pH levels. A hydrogel with high conversion and high swelling degree was selected to investigate their ability for adsorption of Pb(II) ions from solutions. Adsorption behavior of Pb(II) ions in a hydrogel was examined as a function of reaction time and concentration of lead ions from a solution of Pb(II) ions. [ABSTRACT FROM AUTHOR]

This study is a new sight to the application of Preyssler heteropolyacid with the formula of [NaP 5 W 30 O 110 14− as a green and nontoxic inorganic crosslinker to prepare a supramolecular hydrogel using chitosan and polyvinyl alcohol. This novel Preyssler/chitosan/polyvinyl alcohol hydrogel was designed using a multicomponent synthesis method and characterized by multiple techniques including infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), force atomic microscopy (AFM), contact angle measurement, mechanical tests and thermogravimetric analysis (TGA). TGA was conducted to measure the weight loss of the synthesized hydrogel at a heating rate of 10 °C min−1 in the nitrogen atmosphere. It is evident that Preyssler is acting as a crosslinker which has high thermal degradation or high thermal stability. The FTIR of the synthesized hydrogel reveals no chemical changes during crosslinking. The resultant surface showed excellent hydrophilic ability and had a water contact angle (CA) of 19.8 ± 4. Results of the SEM revealed that the surface of the hydrogel film is homogeneous and continuous. The sample had a low elongation at break (1.84 ± 2.38%), due to strong hydrogen bonding interactions between the Preyssler, chitosan, and PVA. The performance of the synthesized hydrogel using Preyssler's anion was compared with chitosan/polyvinyl alcohol. In all cases, the maximum improvement was observed by using the Preyssler heteropolyacid. To expand the potential application of the synthesized hydrogel in water treatment, the removal of methyl orange and red pigment as common azo dye pollutants in the environment was selected as a test reaction to estimate the potential application of the synthesized hydrogel and found to be excellent. • This study is a new sight to the application of Preyssler heteropolyacid as crosslinker. • Preyssler/chitosan/polyvinyl alcohol hydrogel was synthesized and fully characterized. • A green and nontoxic inorganic crosslinker used to prepare supramolecular hydrogel. • The process as a green technology does not require harmful and corrosive crosslinkers. • The synthesized hydrogel is a good candidate to remove azo dyes from color wastewaters. [ABSTRACT FROM AUTHOR]

Alginate and polyacrylamide hydrogels were produced by a facile one‐pot method with varied ionic crosslinkers in this article. These hydrogels display outstanding mechanical properties compared to the pristine polyacrylamide (PAAm) hydrogels. The alginate network is ionically crosslinked by multivalent cation, whereas N,N′‐methylenebis (acrylamide) (MBAA) is used as covalent crosslinker for the PAAm network. Particularly, the obtained hydrogels by using trivalent cations (Fe3+ and Al3+) as crosslinkers are much stronger than that of using divalent cations (Ca2+ and Ba2+) as crosslinkers. In addition, with increasing concentration of cations, the compressive properties of gels are improved, whereas when the concentration is higher than 0.3 M, the compressive properties of gels are damaged due to mono‐bindings. Interestingly, the hydrogels with higher chemical crosslinker concentration depicts better mechanical properties than those hydrogels with lower chemical crosslinker, which is different from that of common double network hydrogels. These hydrogels with excellent mechanical properties are promising candidates for biomedical application like load‐bearing tissues. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48182. [ABSTRACT FROM AUTHOR]

Highlights from the article: Summary: Superabsorbent hydrogels constitute a group of polymeric materials with three- Hydrogels based on acrylic acid-co-acrylamide copolymers were synthesized under variation of Keywords: Superabsorbent; Hydrogels; Hydrophilic polymer; Crosslinker; Monomer concentration. Hydrogels, Superabsorbent, Crosslinker, Hydrophilic polymer, Monomer concentration.

In this work, we report a facile strategy to synthesize ferrohydrogel containing magnetic nanoparticle as crosslinker and successfully using as draw agent in forward osmosis processes. Herein, a core-shell magnetic nanoparticle was synthesized to use as a crosslinker in hydrogel matrix by coating 3-(trimethoxysilyl) propyl methacrylate (MPS) shell onto Fe3O4@SiO2 nanoparticles. Ferrohydrogel is synthesized by free radical polymerization of acrylic acid (AA) and acrylamide (AAm) as monomers and Fe3O4@SiO2@MPS as crosslinker (MNP-FHg). Conventional crosslinked pure polymer hydrogel (MBA-PHg) and ferrohydrogel (MBA-FHg), using methylene bisacrylamide (MBA) crosslinker, are compared to those obtained by Fe3O4@SiO2@MPS multifunctional crosslinker. The water flux and swelling ratio yielded by MNP-FHg was investigated and compared with MBA-PHg and MBA-FHg under the same operating condition. The results show the high swelling ratio and water flux for MNP-FHg in comparison to other hydrogel samples and confirmed the significant effect of crosslinker on the performance of polymer hydrogel. Furthermore, thanks to the existence of MNPs, this ferrohydrogel can be easily recovered from the diluted draw solution under an external magnetic field.ᅟ [ABSTRACT FROM AUTHOR]