Search Results (150)

Most existing polymer plastics are nonreusable and also exhibit poor biocompatibility and a poor mechanical strength–tensile strain balance. Herein, using deep eutectic polymers, we prepare reusable hydrophilic supramolecular dry gel plastics with balanced stress–strain characteristics through the hydrogen bonding of poly(vinyl alcohol) (PVA) with betaine (Bta). As PVA exhibits crystalline stiffness and abundant hydrogen-bonding sites, it is employed as a network backbone in the proposed deep eutectic supramolecular polymers. In the prepared PVA/Bta dry gel plastics, PVA and Bta are dynamically and physically crosslinked through high-density hydrogen bonding, resulting in a yield strength of ~109 MPa and toughness of up to ~210.92 MJ m⁻³. In addition, these plastics can be recycled at least five times in an aqueous environment while maintaining a mechanical strength of 100 MPa. Furthermore, the proposed polymers exhibit high transparency (92%) in the visible spectrum. We expect these polymers to be used in synthesizing biodegradable dry gel plastics, as well as to lead to the development of recyclable deep eutectic PVA/Bta polymers with remarkable strength. Full article

This paper reports several preliminary investigations concerning the relative humidity (RH) detection response of a chemiresistive sensor that uses a novel sensing layer based on pristine carbon nano-onions (CNOs) and polyvinyl alcohol (PVA) at a 1/1 and 2/1 w/w ratio. The sensing device, including a Si/SiO₂ substrate and gold electrodes, is obtained by depositing the CNOs–PVA aqueous suspension on the sensing structure by drop casting. The composition and morphology of the sensing film are explored by means of scanning electron microscopy, Raman spectroscopy, atomic force microscopy, and X-ray diffraction. The manufactured sensor’s room temperature RH detection performance is examined by applying a continuous flow of the electric current between the interdigitated electrodes and measuring the voltage as the RH varies from 5% to 95%. For RH below 82% (sensing layer based on CNOs–PVA at 1/1 w/w ratio) or below 50.5% (sensing layer based on CNOs–PVA at 2/1 w/w ratio), the resistance varies linearly with RH, with a moderate slope. The newly developed sensor, using CNOs–PVA at a 1:1 ratio (w/w), responded as well as or better than the reference sensor. At the same time, the recorded recovery time was about 30 s, which is half the recovery time of the reference sensor. Additionally, the changes in resistance (ΔR/ΔRH) for different humidity levels showed that the CNOs–PVA layer at 1:1 was more sensitive at humidity levels above 80%. The main RH sensing mechanisms considered and discussed are the decrease in the hole concentration in the CNOs during the interaction with an electron donor molecule, such as water, and the swelling of the hydrophilic PVA. The experimental RH detection data are analyzed and compared with the RH sensing results reported in previously published work on RH detectors employing sensing layers based on oxidized carbon nanohorns–polyvinylpirrolidone (PVP), oxidized carbon nanohorns–PVA and CNOs–polyvinylpyrrolidone. Full article

This study aimed to analyze the effects of PVA aqueous solution as a new foaming agent, and the production and characteristics of ultralight foam concrete using a mixed lightweight aggregate of perlite (PL) and cenosphere (CP). In addition, the application of a new high-temperature curing process was proposed to improve the foaming effect of PVA and reduce the weight of concrete. The mixing ratios (s/c) of the PVA solution and OPC were 1.0, 1.5, and 2.0, and the ratio of the PVA solution–OPC–lightweight aggregate (perlite and cenosphere) (s/(c + CP + PL)) was 0.43–1.0. As a result, an ultralight foam concrete with a dry density of less than 1.0 g/cm³, an average pore diameter of 0.1–2.3 mm, and a compressive strength of 1.5–10.5 MPa could be manufactured. From the experimental results, PVA showed sufficient usability as a foaming agent. And the new high-temperature curing process proposed in this study could be suggested as a method applicable to the expansion of pores and lightweight reduction in the manufacture of foamed concrete. The diameter of the foamed pores changed depending on the mixing ratio of CP and PL, and the diameter of the foamed pores increased as the ratio of PL increased. However, an increase in the ratio of CP improved the insulation properties. The increase in the OPC ratio increased the mechanical strength, but increased the dry density and decreased the insulation properties. Therefore, the mixing ratio of CP and PL was an important factor affecting the properties of ultralight foam concrete. From the experimental results, PVA was suggested to have sufficient potential as a new foaming agent, and the new high-temperature curing process proposed in this study is expected to be applicable to the production of foam concrete using PVA. Full article

In this study, we designed the preparation method and application study of chitosan–polyvinyl alcohol–chrysanthemum extract–nanosilver composite gel (CTS/PVA/Ag/CHR), constructed a composite gel system with chitosan/polyvinyl alcohol as the carrier, and utilized chrysanthemum extract within the gel to convert silver nitrate into nanosilver via green reduction. In the bacterial inhibition experiments, the CTS/PVA/Ag/CHR gel showed excellent antibacterial properties, and the diameter of the inhibition circle for Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa by the agar diffusion method was 32.5 mm, 30.5 mm, and 34.0 mm, respectively. In the aqueous bacterial inhibition experiments, the gel’s inhibition rate against the three kinds of bacteria was 100% after 5 h. The abundant hydroxyl groups contained in the polyvinyl alcohol (PVA) formed hydrogen bonds with the amino groups present in chitosan (CTS), which maintained the stability of the gel structure and enhanced the moisturizing and water storage properties of the gel. The adsorption curves of the CTS/PVA/Ag/CHR gel were fitted using a proposed pseudo-second-order kinetic model. Methylene blue, methyl orange, Congo red, and malachite green were discovered to have strong adsorption capacities, with the most significant adsorption effect for methyl orange at 205.65 mg/g. Moreover, the CTS/PVA/Ag/CHR gel showed good freshness preservation in milk simulation experiments. Due to its superior adsorption capability and antibacterial qualities, the CTS/PVA/Ag/CHR gels have great potential for applications in wastewater purification and food preservation. Full article

Objectives: Anthropomorphic phantoms offer a promising solution to minimize animal testing, enable medical training, and support the efficient development of medical devices. The adjustable mechanical, biochemical, and imaging properties of the polyvinyl alcohol cryogel (PVA-C) make it an appropriate phantom material for mimicking soft tissues. Conventional manufacturing (CM) of aqueous solutions requires constant stirring, using a heated water bath, and monitoring. Methods: To explore potential improvements in the dissolution of PVA crystals in water, a microwave-based manufacturing method (MWM) was employed. Samples created using CM and MWM (n = 14 each) were compared. Because PVA-C is a multifunctional phantom material (e.g., in magnetic resonance imaging (MRI)), its MRI properties (T1/T2 relaxation times) and elasticity were determined. Results: T1 relaxation times did not significantly differ between the two methods (p = 0.3577), whereas T2 and elasticity for the MWM were significantly higher than those for the CM (p < 0.001). The MWM reduced the production time by 11% and decreased active user involvement by 93%. Conclusions: The MWM offers a promising, easily implementable, and time-efficient method for manufacturing PVA-C-based phantoms. Nevertheless, manufacturing-related microstructural properties and sample molding require further study. Full article

There is currently a demand for anti-adhesive materials that are capable of preventing the formation of intra-abdominal adhesions. In this study, electrospun poly(lactide-co-glycolide) scaffolds were dip-coated in aqueous solutions of polyvinyl alcohol with concentrations of 3 wt.%, 6 wt.% and 9 wt.% to obtain a nontoxic and anti-adhesive biomedical material. The viscosities of the applied 3 wt.%, 6 wt.% and 9 wt.% polyvinyl alcohol solutions were 7.7 mPa∙s, 38.2 mPa∙s and 180.8 mPa∙s, respectively, and increased exponentially. It is shown that increasing the viscosity of the polyvinyl alcohol solution from 6 wt.% to 9 wt.% increases the thickness of the polyvinyl alcohol layer from (3.32 ± 0.97) µm to (8.09 ± 1.43) µm. No pronounced polyvinyl alcohol layer can be observed on samples dip-coated in 3 wt.% PVA solution. Increasing the viscosity of the polyvinyl alcohol solution from 3 wt.% to 9 wt.% increases the mechanical properties of the poly(lactide-co-glycolide) samples by a factor of 1.16–1.45. Cytotoxicity analysis of all samples reveals that none is toxic to 3T3-L1 fibroblast cells. A cell adhesion assay indicates that the anti-adhesion properties increase with increasing viscosity of the polyvinyl alcohol solution and the thickness of the polyvinyl alcohol layer on the poly(lactide-co-glycolide) scaffolds. Fluorescence images of the cells show that as the thickness of the polyvinyl alcohol coating increases, the number of cells decreases, and they do not cover the surface of the samples and form spherical three-dimensional agglomerates. The highest mechanical and anti-adhesion properties are obtained with the poly(lactide-co-glycolide) scaffold sample dip-coated in the 9 wt.% polyvinyl alcohol solution. This is because this sample has the thickest polyvinyl alcohol coating. Full article

Sustainability requirements must be met by the appropriate selection of efficient and environmentally friendly materials and processes. We present materials obtained via all-in-water methods: first, few-layer graphene (FLG)–polyvinyl alcohol (PVA) colloids and then electrospun PVA-FLG fibers. The effects of the FLG concentration, and indirectly of ultrasound, are reflected via the modification of the structural and physical properties, including the microstructure, viscosity, thermal degradation and mechanical properties, of colloids and fiber mats. The primary results are highly encouraging for further optimization and the development of conductive, and mechanically resistant, materials. Full article

The development of nanofibers with incorporated biologically active molecules with a targeted mode of action is a current research trend. Potential materials for the development of such systems include poly(vinyl alcohol) (PVA) and chitosan (CS) nanofibers, which are traditionally fabricated by the electrospinning of aqueous solutions of these polymers with acetic acid. To improve drug integration, ethanol was added to the binary-solvent system. This results in several important data: noticeable shifts in the solvent system’s solubility parameter, the interaction of the various component forces, and optical and rheological properties of the PVA-CS solution. The use of ethanol in the electrospun solution also contributes to adjusting the solubility parameters of the solution in the Teas graph, maintaining the “f_h − f_d” in the optimal region for the fabrication of PVA-CS nanofibers. Increasing the efficiency of PVA-CS nanofiber fabrication by electrospinning is quite difficult due to the requirements of solution parameters, technological parameters, and environmental parameters; however, this efficiency was increased in this work by 2 to 3 times with a more optimal PVA-CS nanofiber morphology. These results demonstrate that aqueous solution containing 4% PVA, 3% CS, 15% ethanol, and 45% acetic acid is optimal for increasing the nanofiber fabrication productivity, improving the morphology and diameter of PVA-CS nanofibers without changing in chemical bonds. The XRD spectrum revealed that the alterations in the crystal lattice and diameter of the PVA-CS nanofibers led to the variation in their thermal and tensile properties. Full article

Polyvinyl alcohol (PVA), possessing a strong ability to form hydrogels, has been widely used for various pharmaceutical and biomedical applications. In particular, the use of PVA-PEG in the form of theta gels for altered cartilage treatment has attracted an enormous amount of attention in the last 20 years. In this paper, we prepared 42 PVA-PEG in the form of theta gels at room temperature in an aqueous environment, testing the crystallization occurrence at basic pH (10 or 12). Using a statistical approach, the effect of PEG molecular weight, PVA molecular weight and alkaline pH values on water content and mechanical performance was evaluated. The used procedure permitted the theta gels to maintain swelling properties comparable to those of human cartilage, from 60% to 85%, with both polymers having the same influence. PEG MW mainly affected the hydrophilic properties, whereas the thermal properties were mostly influenced by the PVA. The shear and compression mechanical behavior of the produced materials were affected by both the polymers’ MWs. The sample obtained using PVA 125 kDa with PEG 20 kDa as a porogen appeared to be the most suitable one for cartilage disease treatment, as it had an equilibrium shear modulus in the range of 50–250 kPa, close to that of native articular cartilage, as well as optimal mechanical response under compression along the entire analyzed frequency range with a mean value of 0.12 MPa and a coefficient of friction (COF) which remained under 0.10 for all the tested sliding speeds (mm/s). Full article

Photochromic inks have shown disadvantages, such as poor durability and high cost. Self-healable hydrogels have shown photostability and durability. Herein, a viologen-based covalent polymer was printed onto a paper surface toward the development of a multi-stimuli responsive chromogenic sheet with thermochromic, photochromic, and vapochromic properties. Viologen polymer was created by polymerizing a dialdehyde-based viologen with a hydroxyl-bearing dihydrazide in an acidic aqueous medium. The viologen polymer was well immobilized as a colorimetric agent into a polyvinyl alcohol (PVA)/tricarboxy cellulose (TCC)-based self-healable hydrogel. The viologen/hydrogel nanocomposite films were applied onto a paper surface. The coloration measurements showed that when exposed to ultraviolet light, the orange layer printed on the paper surface switched to green. The photochromic film was used to develop anti-counterfeiting prints using the organic hydrogel composed of a PVA/TCC composite and a viologen polymer. Reversible photochromism with strong photostability was observed when the printed papers were exposed to UV irradiation. A detection limit was monitored in the range of 0.5–300 ppm for NH_3(aq). The exposure to heat (70 °C) was found to reversibly initiate a colorimetric change. Full article

In this research, silver-loaded biochar (C-Ag) was acquired from a waste fish scale, and nanocellulose (CNF) was prepared from the waste wheat stalk. Then C-Ag was loaded into chitosan-polyvinyl alcohol hydrogel (CTS-PVA) with CNC as a reinforcement agent, and a novel nanocomposite material was acquired, which could be efficiently applied for antibacterial and dye removal. By plate diffusion analysis, the inhibition areas of C-Ag-CTS-PVA-CNF (C/CTS/PVA/CNF) hydrogel against E. coli ATCC25922, S. aureus ATCC6538, and P. aeruginosa ATCC9027 could reach 22.5 mm, 22.0 mm, and 24.0 mm, respectively. It was found that the antibacterial rate was 100% in the water antibacterial experiment for 2 h, and the antibacterial activity was more than 90% within 35 days after preparation, and the antibacterial rate was more than 90% after repeated antibacterial tests for five times. Through swelling, water adsorption, water loss rate, and water content tests, the hydrogel manifested good moisturizing properties and could effectually block the loss of water and improve the stability of the C/CTS/PVA/CNF hydrogel. The pseudo-first-order and pseudo-second-order models were built, and the adsorption capacity of hydrogel to dye was analyzed, and the dye removal was more consistent with the pseudo-first-order kinetic model. The best removal effect for Congo red was 96.3 mg/g. The C/CTS/PVA/CNF hydrogel had a remarkable removal efficacy on Malachite green, Methyl orange, Congo red, and Methylene blue. As a result, the C/CTS/PVA/CNF hydrogels had robust antibacterial properties and reusability. In addition, the present research developed a facile strategy for effectual dyes removal from the aqueous medium. Full article

Composite polymer membranes were obtained using the so-called dry phase inversion and were used for desalination of diluted saline water solutions by pervaporation (PV) method. The tests used a two-layer backing, porous, ultrafiltration commercial membrane (PS20), which consisted of a supporting polyester layer and an active polysulfone layer. The active layer of PV membranes was obtained in an aqueous environment, in the presence of a surfactant, by cross-linking a 5 wt.% aqueous solution of polyvinyl alcohol (PVA)—using various amounts of cross-linking substances: 50 wt.% aqueous solutions of glutaraldehyde (GA) or citric acid (CA) or a 40 wt.% aqueous solution of glyoxal. An ethylene glycol oligomer (PEG 200) was also used to prepare active layers on PV membranes. Witch its help a chemically cross-linked hydrogel with PVA and cross-linking reagents (CA or GA) was formed and used as an active layer. The manufactured PV membranes (PVA/PSf/PES) were used in the desalination of water with a salinity of 35‰, which corresponds to the average salinity of oceans. The pervaporation method was used to examine the efficiency (productivity and selectivity) of the desalination process. The PV was carried at a temperature of 60 °C and a feed flow rate of 60 dm³/h while the membrane area was 0.005 m². The following characteristic parameters of the membranes were determined: thickness, hydrophilicity (based on contact angle measurements), density, degree of swelling and cross-linking density and compared with the analogous properties of the initial PS20 backing membrane. The physical microstructure of the cross-section of the membranes was analyzed using scanning electron microscopy (SEM) method. Full article

Zn–air batteries (ZABs) are a promising technology; however, their commercialization is limited by challenges, including those occurring in the electrolyte, and thus, gel polymer electrolytes (GPEs) and hydrogels have emerged as substitutes for traditional aqueous electrolytes. In this work, PVA/PAA membranes were synthesized by the solvent casting method and soaked in 6 M KOH to act as GPEs. The thickness of the membrane was modified (50, 100, and 150 μm), and after determining the best thickness, the membrane was modified with synthesized SiO₂ nanospheres and multi-walled carbon nanotubes (CNTs). SEM micrographs revealed that the CNTs displayed lengths of tens of micrometers, having a narrow diameter (95 ± 7 nm). In addition, SEM revealed that the SiO₂ nanospheres had homogeneous shapes with sizes of 110 ± 10 nm. Physicochemical experiments revealed that SiO₂ incorporation at 5 wt.% increased the water uptake of the PVA/PAA membrane from 465% to 525% and the ionic conductivity to 170 mS cm⁻¹. The further addition of 0.5 wt.% CNTs did not impact the water uptake but it promoted a porous structure, increasing the power density and the stability, showing three-times-higher rechargeability than the ZAB operated with the PVA/PAA GPE. Full article

The current work presents a new structure based on Au/PVA/SiO₂/p-Si/Al that has not been studied before. An aqueous solution of polyvinyl alcohol (PVA) polymer gel was deposited on the surface of SiO₂/Si using the spin-coating technique. The silicon wafer was left to be oxidized in a furnace at 1170 k for thirty minutes, creating an interdiffusion layer of SiO₂. The variations in the dielectric constant (Є′), dielectric loss (Є″), and dielectric tangent (tanδ) with the change in the frequency, voltage, and temperature were analyzed. The results showed an increase in the dielectric constant (Є′) and a decrease in the dielectric loss (Є″) and tangent (tanδ); thus, the Au/PVA/SiO₂/p-Si/Al heterostructure has opened up new frontiers for the semiconductor industry, especially for capacitor manufacturing. The Cole–Cole diagrams of the Є″ and Є′ have been investigated at different temperatures and voltages. The ideality factor (n), barrier height (Φ_b), series resistance (R_s), shunt resistance (R_sh), and rectification ratio (RR) were also measured at different temperatures. Full article

Implementing efficient and cost-effective wastewater treatment methods in wastewater treatment plants (WWTPs) is crucial for ensuring sustainable development in contemporary societies. This study explores the feasibility of a continuous UV/${\mathrm{H}}_2{\mathrm{O}}_2$ tubular photoreactor as a pre-treatment to enhance the biodegradability of aqueous polyvinyl alcohol (PVA) solutions, known as a nonbiodegradable wastewater. Using a combination of a Box–Behnken design (BBD) and the response surface methodology (RSM), three main process variables, including the PVA feed concentration, the inlet ${\mathrm{H}}_2{\mathrm{O}}_2$ concentration, and the PVA feed flow rate, are studied within ranges of 500–1500 mg/L, 390–780 mg/L, and 50–150 mL/min, respectively. The results show significant interaction effects between the PVA feed and inlet ${\mathrm{H}}_2{\mathrm{O}}_2$ concentrations on the effluent ${\mathrm{B}\mathrm{O}\mathrm{D}}_5$/COD ratio. The optimal operating conditions are determined using the RSM, with a PVA feed concentration of 665 mg/L, an inlet ${\mathrm{H}}_2{\mathrm{O}}_2$ concentration of 390 mg/L, and a PVA feed flow rate of 59 mL/min. Operating at this point leads to an increase in the effluent ${\mathrm{B}\mathrm{O}\mathrm{D}}_5$/COD ratio from 0.15 to 0.53, which is validated experimentally with a ±5% error. Under these conditions, the effluent demonstrates an enhanced biodegradability, allowing for redirection to a subsequent biological post-treatment phase. This study demonstrates that using the UV/${\mathrm{H}}_2{\mathrm{O}}_2$ process to enhance the biodegradability of an aqueous PVA solution is more economical than focusing on the complete removal of total organic carbon (TOC). Also, a comparison of these results with those of our previous study indicates that wastewater becomes more biodegradable by progressing the UV/${\mathrm{H}}_2{\mathrm{O}}_2$ process due to the breakdown of polymer molecules, which reduces their molecular weight and makes them more consumable for biomass. Full article