Vinyl Alcohol Research Articles

Terahertz Detection of Acid Blue 113 Dye Using Hybrid Hydrogels

AbstractThe detection of pollutant dyes in the environment, particularly in waterways, can be extended and potentially simplified using terahertz spectroscopy. The use of hydrogels to absorb these contaminants from water and create solid samples with moderate transparency at terahertz frequencies evidently facilitates spectroscopic analysis. In this study, we demonstrate that chitosan and poly(vinyl alcohol) hydrogels, as well as their cross-linked and nanocomposite hybrid blends, efficiently capture the acid blue 113 azo dye (AB113). We show that terahertz transmittance and refractive index measurements conducted on these hydrogel materials offer an effective alternative method for detecting water contaminants, especially azo dyes. The terahertz transmittance spectra provide evidence of azo dye molecules within the hydrogel membranes. Additionally, considering the alterations in the hydrogels’ refractive index due to the sorption of AB113 dye molecules, we derived an analytical model to accurately estimate the amount of dye sorbed by the polymeric networks. The findings of this study establish a practical and promising approach for both qualitative and quantitative terahertz detection of AB113 dye using hybrid hydrogels. A detailed comparison with optical and infrared spectroscopy is also provided for reference.

Thermoelectric Hydrogel Electronic Skin for Passive Multimodal Physiological Perception.

Electronic skins (e-skins) are being extensively researched for their ability to recognize physiological data and deliver feedback via electrical signals. However, their wide range of applications is frequently restricted by the indispensableness of external power supplies and single sensory function. Here, we report a passive multimodal e-skin for real-time human health assessment based on a thermoelectric hydrogel. The hydrogel network consists of poly(vinyl alcohol)/low acyl gellan gum with [Fe(CN)6]4-/3- as the redox couple. The introduction of glycerol and Li+ furnishes the gel-based e-skin with antidrying and antifreezing properties, a thermopower of 2.04 mV K-1, fast self-healing in less than 10 min, and high conductivity of 2.56 S m-1. As a prospective application, the e-skin can actively perceive multimodal physiological signals without the need for decoupling, including body temperature, pulse rate, and sweat content, in real time by synergistically coupling sensing and transduction. This work offers a scientific basis and designs an approach to develop passive multimodal e-skins and promotes the application of wearable electronics in advanced intelligent medicine.

Self-Healing Composite Coating Fabricated with a Cystamine Cross-Linked Cellulose Nanocrystal-Stabilized Pickering Emulsion.

A gelled Pickering emulsion system was fabricated by first stabilizing linseed oil droplets in water with dialdehyde cellulose nanocrystals (DACNCs) and then cross-linking with cystamine. Cross-linking of the DACNCs was shown to occur by a reaction between the amine groups on cystamine and the aldehyde groups on the CNCs, causing gelation of the nanocellulose suspension. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the cystamine-cross-linked CNCs (cysCNCs), demonstrating their presence. Transmission electron microscopy images evidenced that cross-linking between cysCNCs took place. This cross-linking was utilized in a linseed oil-in-water Pickering emulsion system, creating a novel gelled Pickering emulsion system. The rheological properties of both DACNC suspensions and nanocellulose-stabilized Pickering emulsions were monitored during the cross-linking reaction. Dynamic light scattering and confocal laser scanning microscopy (CLSM) of the Pickering emulsion before gelling imaged CNC-stabilized oil droplets along with isolated CNC rods and CNC clusters, which had not been adsorbed to the oil droplet surfaces. Atomic force microscopy imaging of the air-dried gelled Pickering emulsion also demonstrated the presence of free CNCs alongside the oil droplets and the cross-linked CNC network directly at the oil-water interface on the oil droplet surfaces. Finally, these gelled Pickering emulsions were mixed with poly(vinyl alcohol) solutions and fabricated into self-healing composite coating systems. These self-healing composite coatings were then scratched and viewed under both an optical microscope and a scanning electron microscope before and after self-healing. The linseed oil was demonstrated to leak into the scratches, healing the gap automatically and giving a practical approach for a variety of potential applications.

Fabrication of pH-Responsive Amphiphilic Poly(Vinyl Alcohol–Methyl Methacrylate) Copolymer Nanoparticles for Application in Cancer Drug Delivery Systems

Fabrication of pH-Responsive Amphiphilic Poly(Vinyl Alcohol–Methyl Methacrylate) Copolymer Nanoparticles for Application in Cancer Drug Delivery Systems

Development of flexible poly vinyl alcohol composite for electromagnetic interference shielding using areca microfiber, cobalt Nps, and rice bran biochar

Development of flexible poly vinyl alcohol composite for electromagnetic interference shielding using areca microfiber, cobalt Nps, and rice bran biochar

A novel poly(vinyl alcohol)/silica composite film with “spherical crystal interlocking structure” and its barrier and enhancement mechanism

Using the semi-crystalline poly(vinyl alcohol) (PVA) as the polymer matrix and silica nanoparticles (SNPs) as the reinforcing filler, composite films with excellent water vapor barrier, high tensile strength, visible light transmission and ultraviolet (UV) shielding performances were constructed via a simple heat treatment process, during which the films underwent dehydration cross-linking and isothermal recrystallization to form a "spherical crystal interlocking structure". Both the dosage and average particle size of SNPs significantly affected the barrier property, and the optimal values were 7 wt% and 15 nm, respectively. The heat treatment further improved the water resistance, mechanical strength, and barrier property to a great extent. Moreover, different theoretical models including Guggenheim Anderson de Boer (GAB), Brunauer Emmett and Teller (BET), Hailwood-Horribon (H-H) model, crystallinity model and Fick's law model were successfully used to explain the water vapor barrier mechanism. The water vapor permeability (WVP) of the optimized composite film was reduced to 2.20 × 10−12 g·m/(m2·Pa·s) at 37°C and 65% RH, while the tensile strength was increased up to 116.8 MPa. In addition, the absorption rate of ultraviolet of the film after heat treatment increased from 13% to 92.0%, while the transmittance of visible light remained above 78%.

Hollow Cuboidal Metal Oxide-Based Asymmetric Electrode Configuration for High-Performance Anion Exchange through Quaternized Pyridine-Poly(vinyl alcohol) @ Metal Hydroxide Nanosheets for Water Dissociation

Hollow Cuboidal Metal Oxide-Based Asymmetric Electrode Configuration for High-Performance Anion Exchange through Quaternized Pyridine-Poly(vinyl alcohol) @ Metal Hydroxide Nanosheets for Water Dissociation

A Paper‐Like Hydrogel for Versatile Information Encryption and Decryption Via Chemical‐Induced Phase Separation

AbstractInformation coding, recording, encryption, and decryption are of great importance in the field of anti‐counterfeiting, especially in the current AI information era. Herein, a paper‐like hydrogel composed of solely H‐bonded poly(vinyl alcohol) (PVA) and poly(n‐vinylcaprolactam) (PNVCL), namely VAPN, is developed for multiple ways of encryption and decryption based on chemical‐induced phase separation. It not only exhibits excellent ability of ink absorption and retention by the noncovalent H‐bonds and n−π* interactions and good mechanical strength but also maintains a negligible volume change during the phase separation that is crucial for the information fidelity. Given that the noncovalent interactions are the driving force to trigger the phase separation in the hydrogel, available chemical inks are numerous ranging from small molecules to polymers. Furthermore, together with thermally induced phase separation, the different dynamic processes of the association and dissociation between ink molecules and the hydrogel endow the latter with reversible information recording and self‐erasing, temporary or permanent, and customized encryption and decryption.

Rapid ellipsometric imaging characterization of nanocomposite films with an artificial neural network.

Imaging ellipsometry is an optical characterization tool that is widely used to investigate the spatial variations of the opto-geometrical properties of thin films. As ellipsometry is an indirect method, an ellipsometric map analysis requires a modeling step. Classical methods such as the Levenberg-Marquardt algorithm (LM) are generally too time consuming to be applied on a large data set. In this way, an artificial neural network (ANN) approach was introduced for the analysis of an ellipsometric map. As a proof of concept this method was applied for the characterization of silver nanoparticles embedded in a poly-(vinyl alcohol) film. We demonstrate that the LM and ANN give similar results. However, the time required for the ellipsometric map analysis decreases from 15 days for the LM to 1 s for the ANN. This suggests that the ANN is a powerful tool for fast spectroscopic-ellipsometric-imaging analysis.

Nanocomposites comprising PVA/CMC matrix and CNTs/Fe2O3 nanohybrid: A comparative investigation of structural, optical, electrical, and dielectric properties as an application in advanced electrochemical and optoelectronic devices

This work addresses the fabrication of innovative flexible polymer nanocomposite films for electrochemical products made of poly (vinyl alcohol) (PVA), carboxymethyl cellulose (CMC), multi-walled carbon nanotubes (CNTs), and hematite (α-Fe2O3) nanoparticles (NPs) as nanohybrid. The PVA/CMC-CNTs/Fe2O3 nanocomposite films were characterized using various approaches. The PVA/CMC blend polymer matrix shows significant improvements in terms of amorphous nature with the CNTs/Fe2O3 nanofiller content, resulting in an exceedingly flexible polymer backbone and with higher ionic conductivity of the PVA/CMC-CNTs/Fe2O3 nanocomposites films, as reported by the XRD examination. The nanoparticle surfaces and the blend matrix exhibit a significant interaction, as seen by the FTIR spectra. To learn more about how CNTs/Fe2O3 NPs affect the optical characteristics of the PVA/CMC, its optical characteristics were examined. The absorption edge appeared to migrate towards lower photon energy sides upon the addition of CNTs/Fe2O3 NPs to the PVA/CMC matrix. The Eg (direct and indirect) of pure PVA/CMC was considerably decreased from 5.12 to 3.55 eV and 4.23 to 3.01 eV respectively by adding 3.5 wt% of CNTs/Fe2O3 NPs. The results proved the influence of the nanofiller on the host polymer's decreased band gap energy. The blend nanocomposite had a substantially higher AC conductivity compared with the blend, and the PVA/CMC-3.5%CNTs/Fe2O3 nanocomposite had the highest electrical conductivity. It was discovered that while the dielectric loss and dielectric constant increased with the high content of nanoparticles, they reduced with increasing frequency. These findings demonstrated that the produced films had undergone substantial changes, which allows for the use of flexible films made of PVA/CMC-CNTs/Fe2O3 in a variety of electrochemical and optoelectronic applications.

Poly (vinyl alcohol) based carbon nanofibers as freestanding anodes for lithium‐ion batteries

AbstractIn this study, we investigated the iodination process for the preparation of water‐soluble polyvinyl alcohol (PVA)‐based carbon nanofibers (CNFs) and their electrochemical properties. Iodinated nanofibers were carbonized at different temperatures (600°C, 800°C) under an argon (Ar) atmosphere. Morphology and physical properties of fiber mats were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and thermogravimetric analysis (TGA), while electrical conductivity measurements were done using four probes. As a freestanding anode in half‐cell lithium batteries, the CNFs were prepared by electrospinning of PVA and PVA–CNT blend, which was exposed to iodine vapor at various temperatures (60, 80, and 100°C). Iodine vapor treatment at 80°C and subsequent carbonization at 800°C provided a 29% carbon yield. The resulting CNT‐containing optimized CNFs exhibited superior flexibility, electrical conductivity (2.16 S/cm), and handleability, making them a promising, binder‐free environmentally friendly carbon source for lithium‐ion batteries with high capacity (672 mAh/g at 50 mA/g). The study clearly showed that PVA might be an alternative precursor for the production of carbon micro‐ and nanofibers.Highlights Anodic performance of PVA‐based carbon nanofibers was analyzed. PVA precursor offers economic and environmental option for binder‐free electrodes. PVA–CNT composite nanofibers with optimized iodination and carbonization time identified as a promising high carbon yield carbon source for lithium‐ion batteries. CNT‐containing optimized carbon nanofibers exhibited superior flexibility and electrical conductivity (2.16 S/cm). Freestanding fiber anodes exhibited a higher capacity of 672 mAh/g, at 50 mA/g compared to conventional graphite anode (372 mAh/g).

Ti3C2Tx MXene- and Sulfuric Acid-Treated Double-Network Hydrogel with Ultralow Conductive Filler Content for Stretchable Electromagnetic Interference Shielding.

Hydrogels are emerging as stretchable electromagnetic interference (EMI) shielding materials because of their tissue-like mechanical properties and water-rich porous cellular structures. However, achieving high-performance hydrogel shields remains a challenge because enhancing conductivity often results in a compromise in deformation adoptability. This work proposes a treatment strategy involving sulfuric acid/titanium carbide MXene, which can simultaneously enhance the conductivity and stretchability of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly(vinyl alcohol) (PVA) double-network hydrogels. Multiple spectroscopic characterizations reveal that sulfuric acid promotes the linear conformation transition of the PEDOT molecular chain, while MXene increases charge delocalization and hydrogen bond cross-linking sites. The hydrogels, synthesized with a combined content of 0.6 wt % of MXene and PEDOT:PSS, exhibit an average X-band EMI SE of 41 dB. This performance is sustained at 94.5%, even following stretching and release at a strain of 200%. Interestingly, the EMI SE is found to linearly increase, reaching a value of 99 dB as the frequency is increased to 26.5 GHz. This increase is attributed to the enhanced water molecular polarization process, as supported by theoretical calculations of the impedance and attenuation constant. This work introduces a post-treatment technique that optimizes double-network hydrogels, providing deep insights into their EMI shielding mechanism and enabling high-performance EMI shielding with an ultralow conductive filler content.

Electrostatic-Interaction-Aided Microneedle Patch for Enhanced Glucose-Responsive Insulin Delivery and Three-Meal-Per-Day Blood-Glucose Regulation.

The phenylborate-ester-cross-linked hydrogel microneedle patch (MNP) was promising in the diabetic field for the glucose-responsive insulin-delivering property and simple fabrication process. However, the unfit design of the charging microneedle network limited the improvement of blood-glucose regulating performances. In this work, insulin-loaded phenylborate-ester-cross-linked MNPs, with the polyzwitterion property, were constructed based on the modified ε-polylysine and poly(vinyl alcohol). The relationship between the charging nature of the MNP network and insulin release was verified by regulating the content of postprotonated positively charged amino groups. The elaborately designed MNP possessed improved glucose-responsive insulin-delivering performance. The in vivo study revealed the satisfactory results on blood-glucose regulation by the optimized MNP under the mimic three-meal-per-day mode. Moreover, the insulin bioactivity in the MNP could be maintained for 2 weeks under 25 °C. In summary, this work developed an effective strategy to improve the glucose-responsive phenylborate-ester-cross-linked MNP and enhance its potential for clinical transformation.

Estimation of Digital Porosity of Electrospun Veils by Image Analysis.

The present work reports on an empirical mathematical expression for predicting the digital porosity (DP) of electrospun nanofiber veils, employing emulsions of poly(vinyl alcohol) (PVOH) and olive and orange oils. The electrospun nanofibers were analyzed by scanning electron microscopy (SEM), observing orientation and digital porosity (DP) in the electrospun veils. To determine the DP of the veils, the SEM micrographs were transformed into a binary system, and then the threshold was established, and the nanofiber solid surfaces were emphasized. The relationship between the experimental results and those obtained with the empirical mathematical expression displayed a correlation coefficient (R2) of 0.97 by employing threshold II. The mathematical expression took into account experimental variables such as the nanofiber humidity and emulsion conductivity prior to electrospinning, in addition to the corresponding operation conditions. The results produced with the proposed expression showed that the prediction of the DP of the electrospun veils was feasible with the considered thresholds.

Fabrication of poly(vinyl alcohol) foam/gel composite used for cold storage by combing molding foaming and freeze-thawing technologies

Ice, the widely used low-temperature storage material, plays an important role in the short-time cold chain transportation. To avoid water leakage caused by ice melting, special encapsulation is needed, but inevitably leads to the single shape and the poor contact between ice and the cooled object. It is urgent to develop a new type of leakage-proof cold storage material. Accordingly, in this paper, by combing the technologies of molding foaming and freeze-thawing, a novel cold storage material containing poly(vinyl alcohol) (PVA) carrier foam and PVA gel was fabricated. PVA carrier foam mainly provided the strength foundation, while PVA gel locked the absorbed water. With the addition of 7.0 wt% PVA gel into PVA carrier foam, denser and uniform cells were formed, endowing the foam/gel composite with good shape retention. Even after 500 times’ cyclic compression, the compression curve of the composite still coincided with the original one. The further introduction of 2.0 wt% NaCl into PVA gel enhanced the cold storage effect of the composite, i.e., the temperature in an incubation box could reach −2.5 °C and be maintained for 16 h. This novel PVA foam/gel composite was expected to be used as cold storage material for cold chain transport, and thus broadening the practical application of PVA.

Injectable Conductive Hydrogel with Self-Healing, Motion Monitoring, and Bacteria Theranostics for Bioelectronic Wound Dressing.

Wounds at joints are difficult to treat and tend to recover more slowly due to the frequent motions. When using traditional hydrogel dressings, they are easy to crack and undergo bacterial infection, difficult to match and monitor the irregular wounds. Integrating multiple functions within a hydrogel dressing to achieve intelligent wound monitoring and healing remains a significant challenge. In this research, a multifunctional hydrogel is developed based on polysaccharide biopolymer, poly(vinyl alcohol), and hydroxylated graphene through dynamic borate ester bonding and supramolecular interaction. The prepared hydrogel not only exhibits rapid self-healing (within 60 s), injectable, conductive and motion monitoring properties, but also realizes in situ bacterial sensing and killing functions. It shows excellent bacterial sensitivity (within 15 min) and killing ability via the changes of electrical signals and photothermal therapy, avoiding the emergence of drug-resistant bacteria. In vivo experiments prove that the hydrogel can promote wound healing effectively. In addition, it displays great electromechanical performance to achieve real-time monitoring and prevent re-tearing of the wound at human joints. The injectable pH-responsive hydrogel with good biocompatibility demonstrates considerable potential as multifunctional bioelectronic dressing for the detection, treatment, management, and healing of infected joint wounds.

Nanoapatite-Loaded κ-Carrageenan/Poly(vinyl alcohol)-Based Injectable Cryogel for Hemostasis and Wound Healing.

Immediate control of excessive bleeding and prevention of infections are of utmost importance in the management of wounds. Cryogels have emerged as promising materials for the rapid release of medication and achieving hemostasis. However, their quick release properties pose the challenge of exposing patients to high concentrations of drugs. In this study, hybrid nanocomposites were developed to address this issue by combining poly(vinyl alcohol) and κ-carrageenan with whitlockite nanoapatite (WNA) particles and ciprofloxacin, aiming to achieve rapid hemostasis and sustained antibacterial effects. A physically cross-linked cryogel was obtained by subjecting a blend of poly(vinyl alcohol) and κ-carrageenan to successive freezing-thawing cycles, followed by the addition of WNA. Furthermore, ciprofloxacin was introduced into the cryogel matrix for subsequent evaluation of its wound healing properties. The resulting gel system exhibited a 3D microporous structure and demonstrated excellent swelling, low cytotoxicity, and outstanding mechanical properties. These characteristics were evaluated through analytical and rheological experiments. The nanocomposite cryogel with 4% whitlockite showed extended drug release of 71.21 ± 3.5% over 21 days and antibacterial activity with a considerable growth inhibition zone (4.19 ± 3.55 cm). Experiments on a rat model demonstrated a rapid hemostasis property of cryogels within an average of 83 ± 4 s and accelerated the process of wound healing with 96.34% contraction compared to the standard, which exhibited only ∼78% after 14 days. The histopathological analysis revealed that the process of epidermal re-epithelialization took around 14 days following the skin incision. The cryogel loaded with WNAs and ciprofloxacin holds great potential for strategic utilization in wound management applications as an effective material for hemostasis and anti-infection purposes.

Hydrogel-Functionalized Bandages with Janus Wettability for Efficient Unidirectional Drug Delivery and Wound Care.

Chronic wounds have imposed a severe physical and economic burden on the global healthcare system, which are usually treated by the delivery of drugs or bioactive molecules to the wound bed through wound dressings. In this work, we have demonstrated a hydrogel-functionalized bandage with Janus wettability in a bilayer structure to achieve unidirectional drug delivery and multifunctional wound care. The Janus patterned bandage with porous gradient wetting channels on the upper layer is responsible for the unidirectional transport of the drug from the outside to the wound bed (up to 90% drug transport efficiency) while preventing drug diffusion in unwanted directions (<8%). The hydrogel composed of chitosan quaternary ammonium salt (HACC), poly(vinyl alcohol) (PVA), and poly(acrylic acid) (PAA) at the bottom layer further functionalized such a bandage with biocompatibility, excellent antibacterial properties, and hemostatic ability to promote wound healing. Especially, the hydrogel-functionalized bandage with Janus wettability exhibits excellent mechanical flexibility (∼198% strain), which can comply well with skin deformation (stretching, bending, or twisting) and maintain unidirectional drug delivery behavior without any leakage. The in vivo full-thickness skin wound model confirms that the hydrogel-functionalized bandage can significantly facilitate epithelialization and collagen deposition and improve drug delivery efficiency, thus promoting wound closure and healing (the wound healing ratio was 98.10% at day 15). Such a synergistic strategy of unidirectional drug delivery and multifunctional wound care provides a more efficient, economical, and direct method to promote wound healing, which could be used as a potential high-performance wound dressing for clinical application.

An Intelligent and Soluble Microneedle Composed of Bi/BiVO4 Schottky Heterojunction for Tumor Ct Imaging and Starvation/Gas Therapy-Promoted Synergistic Cancer Treatment.

Phototherapy and sonodynamic therapy (SDT) are widely used for the synergistic treatment of tumors and have received considerable attention. However, an inappropriate tumor microenvironment, including pH, H2O2, oxygen, and glutathione levels, can reduce the therapeutic effects of synergistic phototherapy and SDT. Here, a novel Bi-based soluble microneedle (MN) is designed for the CT imaging of breast tumors and starvation therapy/gas therapy-enhanced phototherapy/SDT. The optimized Bi/BiVO4 Schottky heterojunction serves as the tip of the MN, which not only has excellent photothermal conversion ability and CT contrast properties, but its heterojunction can also avoid the rapid combination of electrons and hole pairs, thereby enhancing the photodynamic/sonodynamic effects. A degradable MN with excellent mechanical properties is fabricated by optimizing the ratios of poly(vinyl alcohol), poly(vinyl pyrrolidone), and sodium hyaluronate. Glucose oxidase (GOx) and diallyl trisulfide are loaded into the MN to achieve tumor starvation and gas therapy, respectively; And the controlled release of GOx and H2S can be achieved under ultrasound or near-infrared laser irradiation. The in vitro and in vivo results demonstrate that this multifunctional MN can achieve high therapeutic efficacy through starvation therapy/gas therapy-enhanced phototherapy/SDT. The designed multifunctional MN provides a prospective approach for synergistic phototherapy and SDT.

Optimization of microencapsulation of polyaspartic acid ester into UV curable epoxy‐acrylate resin using Taguchi method of experimental design

AbstractDue to fast reaction with isocyanates, polyaspartic acid esters (PAAE) can be used for the development of microcapsules for self‐healing coatings. Microcapsules with encapsulated PAAE into shell formed by UV‐cured commercial epoxy‐acrylate resin were produced through oil‐in‐water emulsion polymerization triggered by UV light. The obtained microcapsules were characterized by FTIR, TGA, optical microscopy, and SEM. Various encapsulation parameters, including core to shell ratio, agitation speed, emulsifier type and concentration, solvent type and its concentration in the oil phase, have been selected at four different levels. Microencapsulation was optimized using Taguchi L16 parameter design approach for determination of desired outcome as larger is better (maximal core content) and nominal is better (microcapsule diameter of 50 μm). It was determined that conditions to prepare microcapsules with the highest core content and the microcapsule size close to 50 μm are rather similar requiring core‐to‐shell ratio at about 4:1, low agitation speed of 500–1000 rpm, and the use of two polymeric emulsifiers poly(vinyl alcohol) and Gum Arabic at concentration of about 2%. Primary benefits of UV‐induced shell formation during microencapsulation of active compounds are remarkably shorter time of the process and possibilities to reach high core content and prepare microcapsules of desirable size.