Swelling Behavior Of Hydrogels Research Articles

Swelling Behaviors of Super-Absorbent Hydrogel based Waste: Bacteria Bran

Firstly, a newly developed bacteria brans (BB) /poly (acrylic/acrylamide/2-acrlylamido-2-methyl-1-propanesulfonic acid) (AA/AM/AMPS) hydrogel was reported, which cross-linked by N, N’-methyl-enebisacrylamide in the presence of potassium persulfate as a free radical initiator. The BB, a waste after the cultivation of the edible fungus, is composite of lignin, cellulose and other carbohydrates, which are beneficial to enhance the water absorbency properties of the super-absorbent hydrogel. Secondly, the chemical structure and morphologies of the hydrogel were characterized by ourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and the thermogravimetric analysis (TGA). The results confirmed that superabsorbent comprised a coarse surface and the porous network structure with carboxylate, carboxamide and sulfate. Finally, the swelling behaviors of the BB/P (AA/AM/AMPS) hydrogel have been studied, achieving favourable water absorbency properties (589 g/g). The effect of swelling behaviors of the hydrogel on the pH value and the concentration of the salt solution were also studied. This work improves the swelling behaviors of the hydrogel. Importantly, it provides the way to devise the hydrogel with environmental compatibility and low-cost, which is useful in many potential applications, such as agriculture.

Swelling Behaviors of Hydrogels with Alternating Neutral/Highly Charged Sequences

Polyelectrolyte gels comprising fixed ions exhibit swelling behaviors because of external solution conditions. Such behaviors are usually explained by using the Flory–Rehner model that considers th...

Swelling behavior of acrylamide and sodium acrylate copolymer hydrogel in aqueous solutions of copper (II) chloride with amino acids additives

Swelling of acrylamide and sodium acrylate copolymer polyelectrolyte hydrogel in aqueous Cu(II) chloride solutions with additives of proteinogenic amino acids glycine and L-histidine has been studied. Research relevance is due to the application of such systems in agrochemical products that are supposed to have high water absorption capacity in the presence of microelements ions and amino acids, which are used to prevent nutritional deficiency and make plants resistant to adverse weather conditions and diseases. Gravimetry, atomic absorption spectrometry, FTIR ATR spectroscopy and molecular absorption spectrophotometry were used. The impact of acidity (pH 3, 5 and 7) of aqueous Cu(II) chloride solutions with amino acids additives on the hydrogel swelling degree and Cu(II) ions absorption has been determined. The reasons for changes in the hydrogel swelling degree in aqueous Cu(II) chloride solutions in presence of glycine and L-histidine have been found. The main product of the crosslinked copolymer interaction with the components of 0.01 M aqueous Cu(II) chloride solution with the addition of 0.04 M glycine or L-histidine at pH 3 has been assumed to be a mixed Cu(II) ions complex with functional groups of both copolymer and amino acids.

Thermosensitive N‐isopropylacrylamide ‐CO‐2‐hydroxyethyl acrylate hydrogels interactions with poly(acrylic acid) and surfactants

Thermosensitive hydrogels based on N‐isopropylacrylamide (NIPAAm) and 2‐hydroxyl ethyl acrylate (2‐HEA) were synthesized with different composition ratios at 50:50 and 70:30 mol% using ammonium persulfate as free radical initiation system. The hydrogel was characterized by Fourier transform infrared spectroscopy (FTIR). The interpolymer complex between hydrogels and linear with poly(acrylic acid) (PAA) with different molecular weight was studied. The effect of pH, molecular weights, inorganic salt (NaCl) as well as surfactants concentrations on the complexation was investigated. The swelling behavior of the thermosensitive hydrogels in PAA solutions went up with increasing pH and molecular weight of PAA. However, the decreasing the concentration of surfactants sodium dodecyl sulfate (SDS) and cetylpyridinium bromide (CPB) increased the swelling behavior of hydrogels.

Coupled thermo-mechanical swelling of a thermo-responsive hydrogel hollow cylinder under extension-torsion: Analytical Solution and FEM

In this article, the mechanical swelling behavior of poly-(N-isopropylacrylamide) hydrogel is scrutinized considering a hollow circular cylinder subjected to temperature variation-extension-torsion. Accordingly, an analytical solution is presented to consider the general combined loading on temperature-sensitive hydrogel cylinder for two approaches, considering same temperature for whole structure and solving heat equation to compute internal temperature of structure. Additionally, to evaluate the proposed solution, finite element analysis has been conducted for same problem which revealed excellent conformity for various case studies. Therefore, a user-material subroutine, UHYPER, is implemented to be employed in finite element analysis in order to define swelling of PNIPAM hydrogels. This subroutine was validated using free swelling and constraint swelling with previous and their analytical solutions. Regarding the complexity of material and loading namely, nonlinear finite behavior of hydrogel as well as combined cooling-extension-torsional loading, various factors, cross-linked density, axial stretch, torsional twist and temperature variation, were investigated to clarify the swelling behavior of hydrogel. Solving heat equation, in the second approach, enables us to apply various thermal conditions on this structure, while in previous studies, the temperature of whole structure is considered to vary simultaneously with the same function. This approach can help researchers to examine diverse thermo-mechanicals problem for temperature-sensitive hydrogels.

Performance of polyvinyl alcohol hydrogel reinforced with lignin-containing cellulose nanocrystals

Lignin-containing cellulose nanocrystals (LCNCs) were produced from old newspapers using the sulfuric acid hydrolysis process, and the product was used in reinforcing polyvinyl alcohol (PVA) based hydrogel. The lignin content of LCNCs was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS), and LCNCs had 8–19 wt% lignin located on their surfaces. The transmission electron microscopy (TEM) confirmed the presence of lignin on LCNCs as small globular-like particles/patches. The increase in the lignin content of LCNCs increased the thermal stability and hydrophobicity while decreasing the crystallinity of LCNCs. Moreover, the effect of LCNC loading (0.1–1 wt%) on the mechanical strength, rheological properties, swelling behavior, morphology, and thermal stability of PVA-based hydrogel was further elucidated. The incorporation of LCNCs in hydrogel at a low dosage improved the swelling behavior of hydrogel. The lignin present on the surface of LCNCs led to enhanced viscoelasticity, increased compressive strength, and improved thermal stability of hydrogel. In addition, the pore size of the hydrogel dropped more significantly (4.26–1.52 μm) with the use of LCNCs containing more lignin. At a low dosage of 0.1 wt%, all studied properties of hydrogels were improved using the LCNC with high lignin content. This study provides a new prospect for the use of lignin-containing CNCs for the production of a high-performance hydrogel.

A smart drug delivery system based on Artemisia vulgaris hydrogel: Design, on-off switching, and real-time swelling, transit detection, and mechanistic studies

Herein, we evaluate the swelling behavior and drug release attributes of Artemisia vulgaris hydrogel (AVH) after pressing into tablet form. The swelling response of AVH tablet and AVH based different tablet formulations of caffeine (CF) and levosulpiride (LS) depicted excellent swelling indices at physiological pH of the gastrointestinal tract (GIT), i.e., 6.8 and 7.4. Inverse swelling response of tablets to different molar concentrations of electrolytes, i.e., NaCl and KCl were observed. All tablets showed reproducible on-off swelling/switching behavior in water and ethanol, water and normal saline, and buffer of pH 7.4 and 1.2. The surface morphology of tablets was observed through a SEM and found porous which facilitates the absorption and retention of aqueous media. Real-time swelling behavior of tablet was observed through MRI. A minute amount of drug was released at pH 1.2, whereas, sustained-release at pH 6.8, 7.4 and in deionized water for 12 h was observed proving AVH as a promising biomaterial for developing pH-responsive sustained drug material. CF and LS release followed zero-order release kinetics and super case II transport mechanism. In vivo X-ray study showed the transit of tablet in GIT. Haemocompatibility studies of AVH confirmed its non-thrombogenic and non-hemolytic nature which broaden its application.

Visco-hyperelastic swelling and mechanical behavior of tough pH-sensitive hydrogels: Theory development and numerical implementation

Tough pH-sensitive hydrogels with noncovalent bonds have been developed in recent years as a promising structural material. They are involved in many engineering devices and natural phenomena due to their attractive properties. In this paper, we develop an electro-chemo-mechanical theory for swelling and mechanical behavior of tough pH-sensitive hydrogels. Due to its large deformation and time-dependent properties, we treat the hydrogel as a single-phase incompressible visco-hyperelastic material. We employ the Nernst-Planck equation to capture the flux of the ionic species through hydrogel boundaries. In this work, we are focused on the macro-size pH-sensitive hydrogels. Due to the Debye length, we assume the electro-neutrality condition both inside and outside of the hydrogel. Therefore, to find the concentration of co-ions and counter-ions inside the hydrogel, we use the Donnan equilibrium. We utilize the Generalized Maxwell model along with the Yeoh strain energy function to characterize the visco-hyperelastic behavior of the hydrogel. Hydrogel swells mainly due to the osmotic pressure. In this theory, we relate the osmotic pressure to the swelling ratio and apply the swelling ratio as a constraint in the strain energy function. After presenting the theory, we implement the theory in a nonlinear finite element framework for simulation. Our proposed theory can capture the transient dual swelling response of the hydrogel in various pH values as well as the time-dependent and self-healing behavior of the hydrogel.

Nanocomposite hydrogel of chitosan-g-poly acrylamide/ nanoclay: effect of degree of cross-linking on their swelling

In this study a chitosan-g-Polyacrylamide hydrogel was prepared through graft copolymerization in the presence of an appropriate amount of potassium persulfate as the initiator and different ratio of methylene bis acrylamide as the crosslinker agent. After dewatering the gels in acetone and being dried in oven, the swelling behaviors of hydrogels in different media such as distilled water, NaCl 0.15M, basic buffer with pH=10 and acidic buffer with pH=3 were evaluated. The gel with the highest swelling degree (i.e. 1/60 crosslinker) was selected to be used in the synthesis of nanocomposite hydrogel. Nanocomposite hydrogels with 1, 3, 5 percent of nanoclay were synthesized respectively. Swelling behaviors of nanocomposite hydrogels were examined. The results of swelling test showed a decrease in the swelling extent as the crosslinker ratio is increased. The result showed that different swelling behaviors as the media of experiment is changed. They showed a lower swelling extent in saline media than in distilled water. The results of swelling test in buffer media show lower swelling extent than in distilled water and swelling extent in acidic buffer with pH=3 is greater than swelling extent in basic buffer with pH=10. The swelling extent of nanocomposite increases slightly with the increase of nanoclay content up to 1%. More increase in the nanoclay content caused a drastic decrease in the swelling extent as well.

Transient swelling behaviour of dual stimuli sensitive nanocomposite hydrogels

Smart nanocomposite hydrogels can undergo large deformation under external stimuli. Several coupled physical processes simultaneously affect the transient swelling behaviour of pH and temperature-sensitive hydrogels. Besides, the hydrogel properties change in response to the external stimuli in the presence of nanoparticles, which affect its transient deformation and swelling behaviour. This work focused on transient swelling modeling of pH and temperature-sensitive polymer/clay nanocomposite hydrogels. The time-dependent processes were considered simultaneously with material properties updating in each time-step during the finite element procedure. A set of experiments was designed to evaluate the numerical solving results in the free and constrained swelling conditions. The results illustrate that the proposed developed model successfully predicts the transient swelling behaviour of pH and temperature-sensitive either for hydrogels or nanocomposite hydrogel counterparts, which can offer a guideline to the abundant usage of these soft materials.

Hydrolysis-induced large swelling of polyacrylamide hydrogels.

Polyacrylamide (PAAm) hydrogels are widely used and studied. Their feature of hydrolysis is often ignored. When PAAm hydrogels are stored under alkaline conditions, they can undergo a hydrolysis reaction, which changes them from neutral hydrogels to polyelectrolyte hydrogels, resulting in significant volumetric increases. In this paper, we establish a non-equilibrium thermodynamic theory to describe hydrolysis-induced large swelling of PAAm hydrogels. In particular, a thermodynamically consistent reaction kinetics is proposed by accounting for auto-retardation of the hydrolysis reaction. As an example, hydrolysis-induced homogeneous swelling under free and constrained boundary conditions is modeled, and we show that mechanical constraints can significantly influence the swelling and reaction of the hydrogels. Our theoretical model is validated by comparing with experiments. This work provides guidelines for understanding and predicting the hydrolysis-induced swelling behavior of PAAm hydrogels under alkaline conditions, and is important for their utilization.

Effects of cellulose nanocrystal polymorphs and initial state of hydrogels on swelling and drug release behavior of alginate-based hydrogels

In this work, composite hydrogels composed of sodium alginate (SA) and two crystal structures of cellulose nanocrystals (CNCs) I and II were prepared, respectively. Impacts of CNC polymorphs and initial state of the hydrogels on the swelling kinetics were analyzed on the basis of power law and Schott’s second-order kinetic equation. It was found that the swelling ratio of SA/1 CNC II was the largest, and it showed the non-Fickian diffusion behavior, while SA and SA/1 CNC I exhibited the Fickian diffusion behavior. And the swelling ratio of soaked hydrogels was great larger than that of the rinsed ones, but the swelling mechanism of the two situations was almost the same, that is, the Fickian diffusion behavior. In addition, drug release tests were performed in deionized water using chloramphenicol as a model drug. The results indicated that for the soaked hydrogels, the drug loading was high, while the release rate was slow. The reason for the higher loading but slower release rate was also discussed based on the morphology of hydrogels. On the other hand, the addition of CNC II into SA brought the high drug loading and slow release rate. It resulted from the strong hydrophilicity of CNC II and the strong interaction between drug and SA/CNC II hydrogels. This work could give a new promise for tuning the swelling and drug release behavior of hydrogels by varying the initial state of hydrogels or the crystal form of CNCs.

Development of a Long-Term Drug Delivery System with Levonorgestrel-Loaded Chitosan Microspheres Embedded in Poly(vinyl alcohol) Hydrogel.

This study reports on the fabrication of a controlled release system for the delivery of levonorgestrel (LNG) for long-term contraception. LNG was encapsulated in chemically cross-linked chitosan (CS) microspheres, and microspheres presented a spherical geometry with a good particle size distribution (polydispersity index (PDI) < 0.1). The LNG-CS microspheres were classified based on their particle size range, <63, 63-125, and 125-300 μm, where the 125-300 μm particles were selected to be incorporated into a physically cross-linked and annealed PVA hydrogel matrix to prolong the drug release. PVA concentrations and the annealing treatment influenced the swelling behavior of PVA hydrogels. Fourier transform infrared (FTIR) spectroscopy indicated that CS was successfully cross-linked through the formation of a Schiff base; the PVA hydrogel was formed through hydrogen bonding without reacting with LNG, which was only physically entrapped, thus maintaining its stability. Differential scanning calorimetry (DSC) showed that freeze-thaw and annealing processes increased the degree of crystallinity in the PVA hydrogel. In vitro drug release assessments for all formulations showed zero order without any burst release. Over a period of 100 days, 34, 27, and 21% of LNG was released from the CS-LNG microspheres in the size ranges < 63, 63-125, and 125-300 μm, respectively, while only 14, 11, and 9% of LNG was released when the CS-LNG microspheres were incorporated into 10, 15, and 20% PVA hydrogels, respectively. The drug release kinetics exhibited both diffusion- and swelling-controlled mechanisms following the Korsmeyer-Peppas model. This work presents a promising delivery system for long-term contraception with controlled zero-order release behaviors.

Magnetic nano carboxymethyl cellulose-alginate/chitosan hydrogel beads as biodegradable devices for controlled drug delivery

For the first time, nano carboxymethyl cellulose (NCMC) was synthesized via cellulose nanocrystal carboxymethylation. This nanomaterial was magnetized and used in bilayer alginate-chitosan hydrogel beads formulation to develop eco-friendly, smart, and magnetic sensitive hydrogel beads for the controlled pH-sensitive release of dexamethasone as a model drug. Water-soluble nanocrystalline cellulose (NCMC) and bilayer hydrogel beads were characterized in terms of size, surface morphology, surface modification, crystallinity, drug loading content, and in vitro drug release profile using various technics. Furthermore, the swelling behavior of hydrogels was examined and reported in three buffer media. The NCMCs improved drug loading capacity and swelling properties and also regulated drug release behavior of hydrogels. The hydrogel beads swelling specification exhibited a higher index in phosphate buffer at pH 5.8 than at pH 1.2 and 7.4. Besides, in vitro release of beads revealed excellent pH-sensitive drug release profiles and prevented release in the gastrointestinal tract. The beads showed high pH sensitivity for dexamethasone drug in pH 5.8 in compared to other pH media. The obtained results could introduce hydrogel beads as a high potential drug delivery system.

Swelling behaviors of novel magnetic semi-IPN hydrogels and their application for Janus Green B removal

Novel magnetic hydrogels based on acrylamide/2-acrylamido-2-methyl-1-propanesulfonic acid/poly(ethylene glycol) were prepared by free radical solution polymerization using ammonium persulfate/N,N,N′,N′-tetramethylethylenediamine as redox initiating pair in the presence of poly(ethylene glycol) dimethacrylate as a cross-linker. In this study, the water uptake and dye sorption performances of a series of novel magnetic hydrogel sorbents were investigated. For the preparation of magnetic polymeric hydrogels and semi-IPNs, they were loaded with iron (Fe2+, Fe3+) ions. Dynamic swelling tests were applied at 25 °C gravimetrically. According to obtained data, swelling kinetics parameters and diffusion mechanisms were calculated. The magnetic hydrogels synthesized in this study showed high water absorbency. Some water uptake and diffusion parameters were calculated, and they were discussed for the hydrogels prepared under various formulations. Structural characterization of polymers was completed with Fourier transform infrared spectroscopy analysis. Scanning electron microscopy images were taken for the determination of surface porosity of hydrogels and semi-IPNs. For adsorption studies, Janus Green B was chosen as model molecule. It was determined that semi-IPNs and hydrogels adsorbed Janus Green B from aqueous solutions at high levels. Consequently, the hydrogels developed in this study could serve for potential applications in wastewater treatment for water and dye uptake.

Swelling behavior of hydrophobic association hydrogels prepared from octylphenol polyoxyethylene (7) acrylate and sodium dodecylsulfate

Hydrophobic association hydrogels (HA-gels) were successfully synthesized from octylphenol polyoxyethylene (7) acrylate (OP-7-AC) and sodium dodecylsulfate (SDS) and their swelling behaviors were studied. Swelling test indicates that the swelling ratio and swelling rate of hydrogel go down first then go up with increased content of SDS. HA-gels exhibited a special “swelling overshoot” phenomenon because of the dissolution of non-gel compositions and surplus SDS. Diffusion of water molecules or the extension of network chains played a major role in the beginning of swelling process of xerogel. With OP-7-AC content increased, swelling ratio of hydrogel and xerogel increased and the “swelling overshoot” became more obvious. At the beginning of swelling, the gel loss increased sharply and then tended to be constant. The gel loss increased with the increase in SDS and OP-7-AC content. The results indicate that SDS and OP-7-AC contents have great effects on the swelling ratio and stability of HA-gels.

Effects of enriching with gellan gum on the structural, functional, and degradation properties of egg white heat-induced hydrogels.

Gellan gum was employed to modulate the technological functionality and in vitro degradation properties of egg white heat-induced hydrogels at different pH values (4.0 and 7.0). The results showed that the enrichment with gellan gum at pH value of 7.0 did not drastically modify the firmness of egg white gel, but at pH 4.0 the addition of gellan significantly improved the hardness and the compressive stress required for the rupturing of the egg white hydrogels. The enrichment with gellan also modulated the swelling behavior of egg white hydrogels as well as significantly improved their water holding capacity. The scanning electron microscopy (SEM) indicated that the composite gellan/egg white hydrogels formed at pH 4.0 and 7.0 had denser microstructures than the corresponding single-component egg white protein hydrogels. The Fourier transform infra-red (FT-IR) spectroscopy also was used to characterize the interactions between egg white proteins and gellan gum. Furthermore, the results revealed that the enrichment of egg white gels with gellan gum drastically increased their stability against in vitro gastrointestinal degradation which can enhance their applications in the site-specific bioactive delivery.

3D Printing of Flexible Liquid Sensor Based on Swelling Behavior of Hydrogel with Carbon Nanotubes

AbstractFlexible sensors with accurate detection of environmental stimuli (e.g., humidity and chemical substances) have drawn increasing research interests in biomedical engineering and environmental science. However, most work is focused on isotropic sensing of liquid occurrence due to the limitation of material development, sensor design, and fabrication capability. 3D printing is used to build multifunctional flexible liquid sensors with multimaterials enabling anisotropic detection of microliquid droplets, and described herein. Electrical conductive composite hydrogels capable of detecting chemical liquid are developed with poly (ethylene diacrylate) (PEGDA) and multiwalled carbon nanotube (MWCNT). Due to the absorption of the liquid droplet and related swelling behavior, the resistance of PEGDA/MWCNT composite hydrogel increases dramatically, while the resistance of pure PEGDA hydrogel decreases significantly. Based on the two composite hydrogels and the related 3D printing method, a mesh‐shaped liquid sensor that can effectively identify the position and volume of liquid leakage in a short time is developed. Furthermore, a three‐layered liquid sensor to enable bidirectional monitor and detection of the liquid leakage in two different sides is demonstrated. The 3D‐printed liquid sensor offers a distinctive perspective on the potential applications in various fields for detection of liquid leakage in accurate position and direction.

Swelling and auramine-O adsorption of carboxymethyl cellulose grafted poly(methyl methacrylate)/Cloisite 30B nanocomposite hydrogels

Carboxymethyl cellulose (CMC) grafted poly(methyl methacrylate)/Cloisite 30B nanocomposite hydrogels were prepared for adsorptive removal of auramine-O (as a cationic dye model) from wastewater. For the synthesis of nanocomposite hydrogel by free radical polymerization method, potassium persulfate (KPS), methyl methacrylate (MMA), N,N′-methylene bisacrylamide (MBA) and Cloisite 30B were used as initiator, monomer, cross-linker and nano-filler, respectively. The nanocomposite hydrogels were characterized by FTIR, TGA, SEM and XRD techniques. The FTIR results showed that the monomer was grafted onto carboxymethyl cellulose chains successfully. Swelling behavior of nanocomposite hydrogel as a function of KPS, MBA, MMA concentration and CMC/Cloisite 30B weight ratio was studied by Taguchi method using Minitab 16 software. According to ANOVA results, the most effective factor of equilibrium swelling of nanocomposite hydrogel was CMC/Cloisite 30B weight ratio. Addition of Cloisite 30B to hydrogel up to a certain amount improved swelling, though its high amount decreased swelling. The effects of pH and ionic strength on swelling of optimum hydrogels were investigated. Maximum swelling of nanocomposite hydrogel occurred at pH 7.0. The kinetic data of adsorption fitted well to pseudo-second-order model. The best isotherm for investigation of adsorption mechanism was Langmuir model suggesting the formation of a monolayer on the adsorbent surface. FTIR results, before and after auramine-O adsorption, showed that complexation is the main mechanism of adsorption. High adsorption capacity of nanocomposite hydrogels made them more efficient in wastewater treatment application.

Ionic-Strength Responsive Zwitterionic Copolymer Hydrogels with Tunable Swelling and Adsorption Behaviors.

In this work, we studied the swelling behavior and adsorption behavior of zwitterionic copolymer hydrogels, which were prepared via the free radical copolymerization of sulfobetaine methacrylate (SBMA) and other monomers including sodium p-styrenesulfonate (NaSS), acrylic acid, N-isopropylacrylamide, and 2-(dimethylamino) ethyl methacrylate. The PSBMA hydrogel showed increased swelling ratio with the increase of ionic strength at the same temperature, and the swelling process reflected endothermicity. Interestingly, the PSBMA-NaSS hydrogels collapsed when the ionic strength increased because the ions can weaken the repulsive interaction of the anionic groups of PNaSS. In addition, the PSBMA-NaSS showed high adsorption of methylene blue (760 mg/g). The zwitterionic hydrogels have potential to be used as an adsorbent in the field of wastewater treatment.