Water In Hydrogels Research Articles

CHARACTERISTICS OF MUTUAL ACTIVATION OF AN INTERGEL SYSTEM BASED ON HYDROGEL POLYMETHACRYL ACID AND POLY-4-VINYL PYRIDINE

The electrochemical properties of mutual activation of polymer networks as a result of remote interaction in an intergel system have been studied. An intergel system consisting of hydrogels of rare crosslinked polymethacrylic acid (hPMAA) and poly-4-vinylpyridine (hP4VP) was chosen as the object of study [1,2]. The purpose of the work is to study the mutual activation features of the intergel system of rare crosslinked hPMAA: hP4VP. The obtained results as the contact time of hydrogels with water increased, zones of maximum and minimum conductivity were observed at the highest points of initial conductivity for different ratios of hPMAA:hP4VP hydrogel systems. In the 6:0 ratio of hPMAA hydrogel, the specific conductivity of the aqueous medium reached its maximum value after one day, and the pH value of the medium decreased relatively to about 4.95. The swelling degree of hPMAA hydrogel was constant at 6:0 different time intervals. In this system, only one polymer, namely hPMAA showed that the hydrogel's water absorption capacity was limited. In the 5:1 ratio of the intergel system, the specific conductivity of the medium reached a high value, and the pH value decreased in the 5:1 ratio. After 2.5 hours of study, a decrease in the conductivity of the aqueous medium was observed at 4:2 hydrogel ratio. After 6 hours, the highest degree of swelling was maintained at 1:5 ratio. In the presence of hP4VP hydrogel at a ratio of 0:6, the pH of the medium increased from 5 to a maximum value of 6.6 within 24 hours. Conclusion. The electrochemical properties of hPMAA:hP4VP hydrogel system were studied by remote interaction. Based on the systematic work, we synthesized the required acidic hydrogel hPMAA:hP4VP and carried out various studies on their properties. To create an intergel system, the obtained hydrogels in seven different proportions were made into an intergel system and their interactions were studied using various physicochemical methods. As a result of the study, the remote interaction of hydrogels in the intergel system leads to conformational changes in their intercellular bonds which undergo additional swelling. As a result of mutual activation, the hydrogels move to a highly ionized state.

A Fluorescent Hydrogel with AIE Emission for Dehydration-Visualizable Wearable Sensors.

Hydrogel-based wearable sensors eventually experience dehydration, which negatively impacts their function, leading to decreased sensitivity. Monitoring the real-time water retention rate and sensing performance of wearable flexible sensors without dismantling them remains a significant difficulty. In this study, a molecule having aggregation-induced emission (AIE) properties in an aqueous environment has been developed and produced, which can combine with anionic guar gum and acrylic acid to create an AIE hydrogel. Wearable sensing electronic devices have the capability to track motion signals at various joints of the human body. Additionally, they can effectively and visually monitor dehydration status during extended periods of operation. The fluorescence intensity of the hydrogel is primarily influenced by the level of aggregation of luminous monomers inside the network. This level of aggregation is predominantly governed by the hydrogel's water retention rate. Hence, the extended duration of hydrogel dehydration can be manifested through alterations in their fluorescence characteristics, which are employed for strain sensing. This approach enables users to assess the water retention of hydrogels with greater efficiency, eliminating the requirement for disassembling them from the completed electrical gadget. In summary, the use of AIE-based fluorescent hydrogels will advance the progress of intelligent wearable electronics.

Synthesis of Polyvinyl Alcohol (PVA)-Gelatin Hydrogel from White Snapper (Lates calcarifer, Bloch) with Gamma Irradiation and Its Characterizations

The application of nuclear technology in the health sector is increasing. One example is the use of irradiation in production of wound dressings. Research activities have been conducted to study whether polyvinyl alcohol (PVA)-gelatin-based hydrogel from white snapper scales can be processed using gamma irradiation into wound dressings. A series of PVA (10 %) solutions containing gelatin in various concentrations (0-4 %) were treated with three freeze-thaw cycles and then irradiated at doses of 10 and 20 kGy. They were subsequently characterized using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM). Gel fraction, water absorption, and percentage of hydrogel water evaporation rate were tested gravimetrically, while the elongation at break and the tensile strength of the hydrogels were tested with a universal testing meter. The evaluation showed that the hydrogel gel fraction decreased with increasing gelatin concentration from 0 % to 4 % for both irradiation doses (10 and 20 kGy). The rising gelatin concentration demonstrated that increasing gamma radiation dose improved the hydrogel's water absorption, evaporation rate, tensile strength, and elongation at break. PVA-gelatin hydrogel with irregular pore structure was observed from SEM test results. The FTIR measurement results confirmed the formation of crosslinks in the hydrogel matrix. The PVA-gelatin hydrogel produced through gamma irradiation could be used for wound dressings.

Fabrication and characterization of biopolymers with antibacterial nanoparticles and Calendula officinalis flower extract as an active ingredient for modern hydrogel wound dressings

Hydrogels are three-dimensional networks that can absorb moisture up to several times their weight and have many medical and biological applications. In this paper, the fabrication and characterization of a three-component chitosan (CS) / sodium alginate (SA) / polyvinyl alcohol (PVA) hydrogel with various weight percentages (0, 5, 10, 15, and 20) wt% of Ag2O/SiO2 with Calendula officinalis flower extract as an active ingredient are fabricated as a novel and green wound dressing. After forming bio-nano composites utilizing the cross-linking technique, Fourier transform infrared (FT-IR) spectroscopy is applied to determine and prove the functional groups added to the CS/PVA/SA at the whole step. X-ray diffraction (XRD) analysis is performed to prove the crystalline and amorphous structure of Ag2O/SiO2 NPs. The field emission scanning electron microscope (FE-SEM) analyses and Energy-dispersive X-ray spectroscopy (EDS) are performed to confirm the morphology of the composition and check the elements to increase wound healing. Atomic force microscope (AFM) examination is done to prove and determine surface roughness and pores. The tensile test is performed to determine the tensile strength and mechanical properties of nanocomposites. Also, by immersing nanocomposites in the simulated body fluid (SBF) and phosphate buffer salt (PBS), the swelling ratio is determined, and the release of Calendula officinalis flower extract is measured in PBS. Finally, the synthesized hydrogel's water vapor transmission rate (WVRT) and then antibacterial tests are determined. This research proves that with the increase of Ag2O/SiO2 NPs to 20% wt., the biofilm's tensile strength and mechanical properties and all healing properties have improved significantly. Producing these films is very effective in improving skin infections. Finally, the thermogravimetric analysis (TGA) is applied to estimate the thermal stability of the biopolymer films with various percentages of mesoporous Ag2O/SiO2 nanoparticles.

A scaling law of particle transport in inkjet-printed particle-laden polymeric drops

Hydrogels with embedded functional particulates are widely used to create soft materials with innovative functionalities. In order to advance these soft materials to functional devices and machines, critical technical challenges are the precise positioning of particulates within the hydrogels and the construction of the hydrogels into a complex geometry. Inkjet printing is a promising method for addressing these challenges and ultimately achieving hydrogels with voxelized functionalities, so-called digital hydrogels. However, the development of the inkjet printing process primarily relies on empirical optimization of its printing and curing protocol. In this study, a general scaling law is proposed to predict the transport of particulates within the hydrogel during inkjet printing. This scaling law is based on a hypothesis that water-matrix interaction during the curing of inkjet-printed particle-laden polymeric drops determines the intra-drop particle distribution. Based on the hypothesis, a dimensionless similarity parameter of the water-matrix interaction is proposed, determined by the hydrogel's water evaporation coefficient, particle size, and mechanical properties. The hypothesis was tested by correlating the intra-drop particle distribution to the similarity parameter. The results confirmed the scaling law capable of guiding ink formulation and printing and curing protocol.

Effect of water content on microstructures and oxygen permeation in PSiMA–IPN–PMPC hydrogel: a molecular simulation study

Grand canonical Monte Carlo combined with molecular dynamics simulation methods are used to investigate the microstructure and oxygen permeability in hydrogels containing interpenetrating poly(bis(trimethylsilyloxy)methylsilylpropyl glycerol methacrylate) (PSiMA) and poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) networks at varying water contents. Water molecules are classified into hydrophilic-hydration water, hydrophobic-hydration water and intermediate water according to their distribution in the hydrogel. As the hydrogel becomes increasingly swollen, three kinds of water molecules concurrently move faster. This leads to the increased water self-diffusion coefficient as the hydrogel's water content is increased. On the contrary, increasing water content in the hydrogel is associated with the decrease of oxygen permeability. This decrease is mainly attributed to the unique transport path of oxygen molecules in the specific hydrogel. Oxygen molecules mainly transport through the PSiMA networks. While the increasing amount of hydrophobic-hydration water molecules occupy oxygen's sorption sites within PSiMA. In addition, higher amount of hydrophobic-hydration water lessens the continuity of free volume in the silicone phase. As a consequence, both oxygen's solubility and diffusivity in the hydrogel are reduced. This contribution anticipates providing some guidance and inspiration for developments of next-generation hydrogel contact lenses.