Acrylic Acid Hydrogel Research Articles

A salt-free poly(acrylic acid) hydrogel electrolyte with self-released ions for quasi-solid-state electrochromic devices

The ionic conductivity of gel polymer electrolytes (GPEs) is usually provided by the added inorganic salt ions. Here, we report a salt-free poly(acrylic acid) (PAA) hydrogel electrolyte with an ionic conductivity of 3.7 × 10−3 S cm−1. The carboxylic groups of PAA can release free H+ ions to provide ionic conductivity, which not only simplifies the preparation of GPEs, but also benefits the fabrication of GPEs with high transparency (>95.6 % from 400 to 1000 nm). The as-prepared hydrogel electrolyte is assembled into an electrochromic (EC) device (ECD) by using Prussian blue/PAA GPE/hydrated tungsten trioxide. The fabricated ECD achieves a high optical modulation (72.7 %), fast responses (2.6 s for coloration and 2.2 s for bleaching), a high coloration efficiency (172.9 cm2 C−1) and good cycling stability (retaining 96.3 % of the original optical modulation after 1200 cycles). Moreover, the ECD has good energy storage properties, demonstrating a potential application for energy-storage smart windows.

Radiation cross-linking of pH-sensitive acrylic acid hydrogel based polyvinylpyrrolidone/ 2-dimethylamino ethyl methacrylate loaded with betamethasone dipropionate drug and in vitro anti-inflammatory assessment

Radiation cross-linking of pH-sensitive acrylic acid hydrogel based polyvinylpyrrolidone/ 2-dimethylamino ethyl methacrylate loaded with betamethasone dipropionate drug and in vitro anti-inflammatory assessment

Colorimetric Sensors Based on Poly(acrylic Acid)/TiO2 Nanocomposite Hydrogels for Monitoring UV Radiation Exposure.

In recent years, there has been an open debate on proper sun exposure to reduce the risk of developing skin cancer. The mainly encountered issue is that general guidelines for UV radiation exposure could not be effective for all skin types. The implementation of customized guidelines requires a method by which to measure the UV dose as a result of daily exposure to sunlight, ideally with an inexpensive, easy-to-read sensor. In this work, we present the characterization of nanocomposite hydrogel materials acting as colorimetric sensors upon exposure to UV light. The sensor was prepared using a poly(acrylic acid) (PAA) hydrogel matrix in which TiO2 nanoparticles and methylene blue (MB) were integrated. Raman mapping was used to determine the network structure of the hydrogel and its water distribution. The TiO2 nanoparticles dispersed in the PAA matrix maintain their photoactivity and catalyze a reaction by which methylene blue is converted into leuko-methylene. The conversion causes a discoloration effect that is visible to the naked eye and can therefore be used as an indicator of UV radiation exposure. Moreover, it was possible to tune the discoloration rate to the limit exposure of each skin type, simply by changing the ratio of titanium dioxide to dye. We obtained a response time ranging from 30 min to 1.5 h. Future work will be dedicated to the possibility of scaling up this range and to improve the sensor wearability; however, our study paves the way to the realisation of sensors suitable for public use, which could help us find a solution to the challenge of balancing sufficient UV exposure to prevent Vitamin D deficiency with excessive UV exposure that could ultimately cause skin cancer.

Improved capacitive performance of polypyrrole-based composite hydrogel for flexible self-powered sensing system

Developing all-gel supercapacitors with high capacitance and stretchability remains a challenge. Herein, high mass of electroactive anthraquinonemonosulfonate(AQS)-doped polypyrrole (PPy) nanoparticles templated by poly(vinyl alcohol) (PVA) have been loaded into poly(acrylic acid) (PAA) hydrogel. The extra energy storage of AQS significantly enhances the electrochemical performance of the obtained PPy-AQS-PVA/PAA hydrogel electrodes. As a result, the assembled symmetrical supercapacitor can deliver a large areal specific capacitance of 392.5 mF/cm2, a high energy density of 34.89 μWh/cm2 and an enhanced cycling performance with 118% capacitance retention after 5000 CV cycles. Besides, such a device can work normally under various deformations and at extreme temperatures. Notably, the PPy-AQS-PVA/PAA hydrogels exhibit sustainable sensing capability for strain. When integrated the flexible supercapacitor with the strain sensor, a promising self-powered sensing system can monitor both large and subtle human movements accurately. Therefore, the multifunctional conductive PPy-AQS-PVA/PAA hydrogels have great potential in flexible electronic devices.

Regulated the Swelling Properties of Poly(acrylamide‐co‐acrylic acid) Hydrogel by Changing the Charge Density

AbstractHydrogels can swell without dissolving in water and are widely used in water treatment and biomedicine. The swelling rate of hydrogels is closely related to the network structure and charge density of hydrogels, but there are few detailed studies in this area. In this work, poly(acrylamide‐co‐acrylic acid) anionic hydrogel with acrylic acid (AA) as anionic monomer is prepared. By changing the monomer ratio, or changing the pH value of hydrogels, the internal charge density can be adjusted, and then the swelling rate can be controlled. With the increase of AA monomer content, the content of carboxylate in hydrogel increases, resulting in higher charge density. A high charge density corresponds to a high swelling rate. On the other hand, the swelling rate is closely related to the pH value, which is because the concentration of proton affects the ionization of carboxylic acid, which leads to the change of charge density. It is worth noting when pH increases to 10, the charge shielding effect of the counter‐ion (Na+) gradually increases, thus limiting the swelling of the hydrogel and reducing the swelling rate. This work has reference value for the practical application of hydrogels.

Self-healing poly(acrylic acid) hydrogels fabricated by hydrogen bonding and Fe3+ ion cross-linking for cartilage tissue engineering

Self-healing poly(acrylic acid) hydrogels fabricated by hydrogen bonding and Fe3+ ion cross-linking for cartilage tissue engineering

Ion-based double network hydrogel with compressive, conductive, and sensing properties for sports monitoring

Conductive hydrogel, as a promising candidate material, is ideal for multifunctional strain sensors due to its similarity to biological tissues. It offers good wearability and high-precision information acquisition. However, fabricating conductive hydrogel-based strain sensors with both superior mechanical and conductive properties remains challenging. In this study, a compressive and conductive strain sensor based on multi-dynamic interactions is fabricated through a simple strategy. The strategy exploits hydrogen bonding and ionic ligand bonding by using nanocellulose reinforced poly(acrylic acid) hydrogels impregnated with the Fe3+ solution to prepare a double-network hydrogel. The prepared PAA/CNF–Fe3+ double-network hydrogel exhibited excellent properties, including extraordinary performance compressive stress (2.96 MPa) and remarkable electrical conductivity (6.34 S/m). With these advantages, the PAA/CNF–Fe3+ double network hydrogel was developed to be an attractive strain flexible sensor with cyclic stability (150 cycles) and good strain sensitivity (GF = 2.87). In addition, the PAA/CNF–Fe3+ hydrogel flexible sensor can be used as an electronic skin to accurately discriminate subtle and large body movements. Given the simple strategy, double network structure, and satisfactory functionality, the PAA/CNF–Fe3+ hydrogel provides a new sustainable and multifunctional development strategy that can be applied in the field of strain sensors and medical detection.

Fabrication and In vitro Evaluation of Carbopol/Polyvinyl Alcohol-based pH-sensitive Hydrogels for Controlled Drug Delivery.

Diclofenac sodium has a short half-life (about 1.5 hours), requiring repeated administration, and as a result, serious complications, such as GI bleeding, peptic ulcer, and kidney and liver dysfunction, are generated. Hence, a sustained/controlled drug delivery system is needed to overcome the complications caused by the administration of diclofenac sodium. This study aimed to fabricate and evaluate carbopol/polyvinyl alcohol-based pH-sensitive hydrogels for controlled drug delivery. pH-sensitive carbopol/polyvinyl alcohol graft-poly(acrylic acid) hydrogels (Cp/PVA-g-PAa hydrogels) were developed for the controlled delivery of diclofenac sodium. The combination of carbopol/polyvinyl alcohol, acrylic acid, and ethylene glycol dimethacrylate was used as polymer, monomer, and cross-linker, respectively. The effects of the formulation's composition on porosity, swelling index, and release pattern of diclofenac sodium from the developed hydrogels were investigated. An increase in porosity and swelling was observed with the increasing amounts of carbopol and acrylic acid, whereas polyvinyl alcohol showed the opposite effect. Due to the formation of a highly viscous system, the drug release decreased with the increasing concentrations of carbopol and polyvinyl alcohol while increased with increasing acrylic acid concentration. The pH-responsive properties of the fabricated hydrogels were demonstrated by dynamic swelling and drug release studies at three different pH values. Higher dynamic swelling and diclofenac sodium (model drug) release were found at high pH values compared to low pH values, i.e., pH 7.4 > 4.6 > 1.2, respectively. Cytotoxicity studies reported no toxic effect of the prepared hydrogels, thus indicating that the prepared hydrogels are safe to be used on clinical basis. The prepared carbopol/polyvinyl alcohol crosslinked hydrogel can be used as a promising carrier for the controlled release of drugs.

Hybrid Hydrogel‐Magnet Actuators with pH‐Responsive Hydrogels for Gastrointestinal Microrobots

Limited space on millimeter‐scale devices for biomedical applications makes it challenging to incorporate bulky actuators and power for onboard mechanical actuation. Stimuli‐responsive hydrogels, such as pH‐responsive hydrogels, provide a solution to automatically sense and actuate in the gastrointestinal tract. However, hydrogels are often nonload bearing and slow in actuation. To overcome these challenges, a new type of hybrid actuator is developed which utilizes a pH‐responsive hydrogel with magnets to trigger magnetic springs (i.e., permanent magnets with repulsive, spring‐like forces) to quickly initiate rotational and translational movements at pH > 6. The agar‐poly(acrylic acid) hydrogel undergoes a large volume transition at pH > 6 and exhibits large nominal blocking stress of 610–819 kPa for a 3–4 mm diameter cylinder hydrogel. Moreover, the scaling of hydrogel force and response times are experimentally confirmed. Based on the hydrogel properties, an analytical hydrogel model is developed to predict hydrogel force and displacement under varying magnetic loads and wall constraints in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 6.8), and the experimental data validate the model. Finally, an innovative hybrid hydrogel‐magnet actuator that triggers rotational and translational motion without external activation is demonstrated.

Phytic acid assist for self-healing nanocomposite hydrogels and their application in flexible strain sensors

Nanocomposite hydrogels have been applied in the field of flexible sensors to monitor human body signals. In this manuscript, phytic acid (PA) was successfully adsorbed on the surface of graphene oxide@polydopamine (GO@PDA). The obtained graphene oxide@polydopamine-phytic acid (GO@PDA-PA) was further implanted to the poly acrylic acid (PAA) hydrogels as flexible strain sensors. Dopamine (DA) was self-polymerized on both two sides of GO by mussel-inspired chemistry to synthetize GO@PDA. PA was decorated on the surface of GO@PDA to obtain GO@PDA-PA nanocomposites with Pickering emulsion in oil-in-water (O/W) emulsion. The GO@PDA-PA hydrogels’ self-healing efficiency (98.6%) and mechanical strength (1.77 MPa) were both improved due to the presence of reversible interaction such as hydrogen bond and metal-ligand coordination. The wearable flexible sensors based on the prepared GO@PDA-PA hydrogels have high sensitivity (gauge factor (GF) = 3.3), stability, durability and high response ability. It can detect the sharp movement signals of human body and tiny movement signals such as breathing. The excellent performance of nanocomposite hydrogels is expected to promote the evolution of flexible sensors.

Network formation and differentiation of chitosan–acrylic acid hydrogels using X-ray absorption spectroscopy and multivariate analysis of Fourier transform infrared spectra

Chitosan–acrylic acid (Cs–AA) hydrogels were prepared by blending different Cs concentrations and AA:Cs ratios. The Cs–AA hydrogel samples were analyzed using synchrotron radiation-induced near edge X-ray absorption fine structure (NEXAFS) and Fourier transform infrared (FTIR) spectroscopies. The characteristics of Cs were observed through the C, O, and N K edges in NEXAFS. Significant shifts in the Cs characteristic features were induced by the addition of AA. The NEXAFS findings confirmed the new covalent and ionic bridges to form the network of the Cs–AA hydrogel. Raw FTIR spectra were used to investigate the different functional groups of each of the macromolecules. The study attempted to discriminate the Cs–AA hydrogels prepared with different Cs wt% concentration and AA:Cs ratio using multivariate approaches. The preprocessed dataset was evaluated using principal component analysis (PCA) and hierarchical cluster analysis (HCA). The PCA and HCA methods showed the possibility of discriminating the Cs–AA hydrogel samples from the control samples and with each other. The approaches further confirmed that the CO groups found in the range of 1700–1800 cm−1 can be used as an identifier for Cs–AA hydrogel samples prepared using different solution parameters. The use of FTIR coupled with multivariate approaches provided a simple and reliable way to inspect the possible discrimination of Cs–AA hydrogels.

Simple and Rapid Way to a Multifunctionally Conductive Hydrogel for Wearable Strain Sensors.

Conductive hydrogels have gained increasing attention in the field of wearable smart devices. However, it remains a big challenge to develop a multifunctionally conductive hydrogel in a rapid and facile way. Herein, a conductive tannic acid-iron/poly (acrylic acid) hydrogel was synthesized within 30 s at ambient temperature by the tannic acid-iron (TA@Fe3+)-mediated dynamic catalytic system. The TA@Fe3+ dynamic redox autocatalytic pair could efficiently activate the ammonium persulfate to initiate the free-radical polymerization, allowing the gelation to occur easily and rapidly. The resulting hydrogel exhibited enhanced stretchability (3560%), conductivity (33.58 S/m), and strain sensitivity (gauge factor = 2.11). When damaged, it could be self-healed through the dynamic and reversible coordination bonds between the Fe3+ and COO- groups in the hydrogel network. Interestingly, the resulting hydrogel could act as a strain sensor to monitor various human motions including the huge movement of deformations (knuckle, wrist) and subtle motions (smiling, breathing) in real time due to its enhanced self-adhesion, good conductivity, and improved strain sensitivity. Also, the obtained hydrogel exhibited efficient electromagnetic interference (EMI) shielding performance with an EMI shielding effectiveness value of 24.5 dB in the X-band (8.2-12.4 GHz). Additionally, it displayed antibacterial properties, with the help of the activity of TA.

Removal of (Crystal Violet, Janus Green) dyes by poly acrylic acid hydrogel beads

Removal of Crystal Violet (C.V) and Janus Green (J.G) dyes was involved when using poly acrylic beads as a surface. The Isotherm of the process were studied and factor that influence it such as (Temperature, ionic strength , Shaking effect , effect of dry beads ) in addition to mixing dyes . According to the results it has been found that the adsorption of the two dyes is matched of the friendlish equation more than the Temkin and Langmuir equation. there is an a positive relationship between the adsorption and increasing of temperature found that the adsorption increasing when the temperature increase . the adsorption increased when the salt added at temperature (20C0). Also, There is a small change when used a wet beads of poly acrylic. adsorption is increasing at shaking when we compare with no shaking of water bath. thermodynamic function were studied (ΔH,ΔG,ΔS) to explain that the process are emitter or absorbent also spontaneous and the random of the process . a kinetic parameter has been studied Lagergren equation ( first order) and by (second order) equations, depending to the results of the experimental, data shown us that the adsorption obeys the pseudo-second order furthermore the first-order equation .

Synthesis and Investigation of the Properties of Biphasic Hybrid Composites Based on Bentonite, Copper Hexacyanoferrate, Acrylamide and Acrylic Acid Hydrogel.

This article presents a study of the synthesis and characterization of new biphasic hybrid composite materials consisting of intercalated complexes (ICC) of natural mineral bentonite with copper hexaferrocyanide (phase I), which are incorporated into the bulk of the polymer matrix (phase II). It has been established that the sequential modification of bentonite with copper hexaferrocyanide and introduction of acrylamide and acrylic acid cross-linked copolymers into its volume by means of in situ polymerization promote the formation of a heterogeneous porous structure in the resulting hybrid material. The sorption abilities of prepared hybrid composite toward radionuclides of liquid radioactive waste (LRW) have been studied, and the mechanism for binding radionuclide metal ions with the components of the hybrid composition have been described.

Copolymer-grafted cellulose nanocrystal induced nanocomposite hydrogels with enhanced strength, high elasticity and adhesiveness for flexible strain and pressure sensors

Recently, the application of cellulose nanocrystals (CNCs) in the field of hydrogel sensors has attracted much attention. However, it remains challenging to construct CNC-reinforced conductive hydrogels with a combination of enhanced strength, low hysteresis, high elasticity and remarkable adhesiveness. Herein, we present a facile method to prepare conductive nanocomposite hydrogels with the above-mentioned properties by reinforcing chemically crosslinked poly(acrylic acid) (PAA) hydrogel with rational-designed copolymer-grafted CNCs. The copolymer-grafted CNCs interact with PAA matrix to form carboxyl-amide conventional hydrogen bonds and carboxyl-amino ionic hydrogen bonds, among which the ionic hydrogen bonds with rapid recovery capability are critical to the low hysteresis and high elasticity of hydrogel. The introduction of copolymer-grafted CNCs endowed the hydrogels with enhanced tensile/compressive strength, high resilience (>95 %) during tensile cyclic loading, rapid self-recovery during compressive cyclic loading and improved adhesiveness. Thanks to the high elasticity and durability of hydrogel, the assembled hydrogel sensors exhibited good cycling repeatability and durability in detecting various strains, pressures and human motions. The hydrogel sensors also showed satisfying sensitivity. Hence, the proposed preparation method and the obtained CNC-reinforced conductive hydrogels would open new avenues in flexible strain and pressure sensors for human motion detection and beyond.

3D printing of mechanically tough and self-healing hydrogels with carbon nanotube fillers.

Hydrogels have the potential to play a crucial role in bioelectronics, as they share many properties with human tissues. However, to effectively bridge the gap between electronics and biological systems, hydrogels must possess multiple functionalities, including toughness, stretchability, self-healing ability, three-dimensional (3D) printability, and electrical conductivity. Fabricating such tough and self-healing materials has been reported, but it still remains a challenge to fulfill all of those features, and in particular, 3D printing of hydrogel is in the early stage of the research. In this paper, we present a 3D printable, tough, and self-healing multi-functional hydrogel in one platform made from a blend of poly(vinyl alcohol) (PVA), tannic acid (TA), and poly(acrylic acid) (PAA) hydrogel ink (PVA/TA/PAA hydrogel ink). Based on a reversible hydrogen-bond (H-bond)-based double network, the developed 3D printable hydrogel ink showed excellent printability via shear-thinning behavior, allowing high printing resolution (~100 μm) and successful fabrication of 3D-printed structure by layer-by-layer printing. Moreover, the PVA/TA/PAA hydrogel ink exhibited high toughness (tensile loading of up to ~45.6 kPa), stretchability (elongation of approximately 650%), tissue-like Young's modulus (~15 kPa), and self-healing ability within 5 min. Furthermore, carbon nanotube (CNT) fillers were successfully added to enhance the electrical conductivity of the hydrogel. We confirmed the practicality of the hydrogel inks for bioelectronics by demonstrating biocompatibility, tissue adhesiveness, and strain sensing ability through PVA/TA/PAA/CNT hydrogel ink.

Synthesis of Cellulose-Poly(Acrylic Acid) Using Sugarcane Bagasse Extracted Cellulose Fibres for the Removal of Heavy Metal Ions.

In this study, sugarcane bagasse (SCB) was treated with sodium hydroxide and bleached to separate the non-cellulose components to obtain cellulose (CE) fibres. Cross-linked cellulose-poly(sodium acrylic acid) hydrogel (CE-PAANa) was successfully synthesised via simple free-radical graft-polymerisation to remove heavy metal ions. The structure and morphology of the hydrogel display an open interconnected porous structure on the surface of the hydrogel. Various factors influencing batch adsorption capacity, including pH, contact time, and solution concentration, were investigated. The results showed that the adsorption kinetics were in good agreement with the pseudo-second-order kinetic model and that the adsorption isotherms followed the Langmuir model. The maximum adsorption capacities calculated by the Langmuir model are 106.3, 333.3, and 163.9 mg/g for Cu(II), Pb(II), and Cd(II), respectively. Furthermore, X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometry (EDS) results demonstrated that cationic exchange and electrostatic interaction were the main heavy metal ions adsorption mechanisms. These results demonstrate that CE-PAANa graft copolymer sorbents from cellulose-rich SCB can potentially be used for the removal of heavy metal ions.

Synthesis and characterization of poly(acrylic acid) hydrogel for doxycycline drug release study

Synthesis and characterization of poly(acrylic acid) hydrogel for doxycycline drug release study

An Anisotropic Hydrogel by Programmable Ionic Crosslinking for Sequential Two-Stage Actuation under Single Stimulus

As one of the most important anisotropic intelligent materials, bi-layer stimuli-responsive actuating hydrogels have proven their wide potential in soft robots, artificial muscles, biosensors, and drug delivery. However, they can commonly provide a simple one-actuating process under one external stimulus, which severely limits their further application. Herein, we have developed a new anisotropic hydrogel actuator by local ionic crosslinking on the poly(acrylic acid) (PAA) hydrogel layer of the bi-layer hydrogel for sequential two-stage bending under a single stimulus. Under pH = 13, ionic-crosslinked PAA networks undergo shrinking (-COO-/Fe3+ complexation) and swelling (water absorption) processes. As a combination of Fe3+ crosslinked PAA hydrogel (PAA@Fe3+) with non-swelling poly(3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl)propane-1-sulfonate) (PZ) hydrogel, the as-prepared PZ-PAA@Fe3+ bi-layer hydrogel exhibits distinct fast and large-amplitude bidirectional bending behavior. Such sequential two-stage actuation, including bending orientation, angle, and velocity, can be controlled by pH, temperature, hydrogel thickness, and Fe3+ concentration. Furthermore, hand-patterning Fe3+ to crosslink with PAA enables us to achieve various complex 2D and 3D shape transformations. Our work provides a new bi-layer hydrogel system that performs sequential two-stage bending without switching external stimuli, which will inspire the design of programmable and versatile hydrogel-based actuators.

The Use of Collagen Methacrylate in Actuating Polyethylene Glycol Diacrylate-Acrylic Acid Scaffolds for Muscle Regeneration.

After muscle loss or injury, skeletal muscle tissue has the ability to regenerate and return its function. However, large volume defects in skeletal muscle tissue pose a challenge to regenerate due to the absence of regenerative elements such as biophysical and biochemical cues, making the development of new treatments necessary. One potential solution is to utilize electroactive polymers that can change size or shape in response to an external electric field. Poly(ethylene glycol) diacrylate (PEGDA) is one such polymer, which holds great potential as a scaffold for muscle tissue regeneration due to its mechanical properties. In addition, the versatile chemistry of this polymer allows for the conjugation of new functional groups to enhance its electroactive properties and biocompatibility. Herein, we have developed an electroactive copolymer of PEGDA and acrylic acid (AA) in combination with collagen methacrylate (CMA) to promote cell adhesion and proliferation. The electroactive properties of the CMA + PEGDA:AA constructs were investigated through actuation studies. Furthermore, the biological properties of the hydrogel were investigated in a 14-day in vitro study to evaluate myosin light chain (MLC) expression and metabolic activity of C2C12 mouse myoblast cells. The addition of CMA improved some aspects of material bioactivity, such as MLC expression in C2C12 mouse myoblast cells. However, the incorporation of CMA in the PEGDA:AA hydrogels reduced the sample movement when placed under an electric field, possibly due to steric hindrance from the CMA. Further research is needed to optimize the use of CMA in combination with PEGDA:AA as a potential scaffold for skeletal muscle tissue engineering.