Vinyl Alcohol Research Articles

Preparation of poly(vinyl alcohol) with enhanced stereoselectivity via hydrolysis of poly(vinyl acetate) produced by radical polymerization using 7-membered ring controlling agents

Controlling tacticity is crucial in polymer chemistry since it impacts the characteristics of synthetic polymers. Poly(vinyl alcohol) (PVA), generally obtained by hydrolysis of poly(vinyl acetate) (PVAc), is a prevalent polymer whose properties are susceptible to even a small change in the main chain stereostructure. Thus, new polymerization methods that improve the tacticity of PVA or its precursor polymer are highly desirable. Herein, 7-membered ring compounds (tropolone (Tro-H), 2-tosyloxytropone (Tro-OTs), potassium tropolonate (Tro-K), methanesulfonic acid, 1,1,1-trifluoro-,7-oxo-1,3,5-cycloheptatrien-1-yl ester (Tro-OTf), potassium 4-((7-oxocyclohepta-1,3,5-trien-1-yl)oxy)butane-1-sulfonate (Tro-SO3K) are explored for the first time as controlling agents for the radical polymerization of VAc with azobisisobutyronitrile (AIBN) as initiator. The obtained PVAc was hydrolyzed to obtain PVA. Process parameters such as monomer concentration, amount of controlling agent and initiators were optimized. The results revealed that the hydrolysis of PVAc produced in the presence of controlling agents gave PVA with improved stereoselectivity. Higher stereoselectivity, that is, isotactic triad (mm) = 24.24% of PVA, was obtained by the hydrolysis of PVAc produced with Tro-SO3K compared to VAc polymerization with other controlling agents. Moreover, hydrolysis of PVAc produced with Tro-SO3K under a wavelength radiation source (λmax, 365 nm) gave PVA with increased mm to 24.59% under similar conditions. In addition, flow chemistry, an emerging technology, was also used for VAc polymerization under optimized reaction conditions to obtain PVA with a mm of 24.62%. This work therefore provides an effective strategy to produce PVA with improved stereoselectivity via both batch and continuous flow techniques, enabling technical advantages for potential large-scale uses.

Lab-made disposable screen-printed electrochemical sensors and immunosensors modified with Pd nanoparticles for Parkinson's disease diagnostics.

Anew conductive ink based on the addition of carbon black to a poly(vinyl alcohol) matrix is developed and investigated for electrochemical sensing and biosensing applications. The produced devices were characterized using morphological and electrochemical techniques and modified with Pd nanoparticles to enhance electrical conductivity and reaction kinetics. With the aid of chemometrics, the parameters for metal deposition were investigated and the sensor was applied tothe determination of Parkinson's disease biomarkers, specifically epinephrine and α-synuclein. A linear behavior was obtained in the range 0.75 to 100μmol L-1 of the neurotransmitter, and the device displayed a limit of detection (LOD) of 0.051μmol L-1. The three-electrode system was then tested using samples of synthetic cerebrospinal fluid. Afterward, the device was modified with specific antibodies to quantify α-synuclein using electrochemical impedance spectroscopy. In phosphate buffer, a linear range was obtained for α-synuclein concentrations from 1.5 to 15μgmL-1, with a calculated LOD of 0.13μgmL-1. The proposed immunosensor was also applied to blood serum samples, and, in this case, the linear range was observed from 6.0 to 100.5μgmL-1 of α-synuclein, with a LOD = 1.3µgmL-1. Both linear curves attend the range for the real diagnosis, demonstrating its potential application to complex matrices.

PVA-based bulk microneedles capable of high insulin loading and pH-triggered degradation for multi-responsive and sustained hypoglycemic therapy.

"Closed-loop" insulin-loaded microneedle patche shows great promise for improving therapeutic outcomes and life quality for diabetes patients. However, it is typically hampered by limited insulin loading capacity, random degradation, and intricate preparation procedures for the independence of the "closed-loop" bulk microneedles. In this study, we combined the solubility of microneedles and "closed-loop" systems and designed poly(vinyl alcohol)-based bulk microneedles (MNs@GI) through in situ photopolymerization for multi-responsive and sustained hypoglycemic therapy, which significantly simplified the preparation process and improved insulin loading. GOx/insulin co-encapsulated MNs@GI with a phenylboronic ester structure improved glycemic responsiveness to control the insulin release under high glucose conditions and reduced inflammation risk in the normal skin. MNs@GI could further degrade to increase insulin release due to the crosslinked acetal-linkage hydrolysis in the presence of gluconic acid, which was caused by GOx-mediated glucose-oxidation in a hyperglycemic environment. The in vivo results showed that MNs@GI effectively regulated glycemic levels within the normal range for approximately 10 h compared to that of only insulin-loaded microneedles (MNs@INS). Consequently, the highly insulin-loaded, multi-responsive, and pH-triggered MN system has tremendous potential for diabetes treatment.

Chitosan/PVA Nanocomposite Films with Improved Structural, Vibrational and Optical Properties

Herein, the solvent costing method was used to prepare the chitosan/poly vinyl alcohol (CS/PVA) nanocomposite films and the properties of structural, vibrational, optical, thermal and electrochemical of these films have been reported. XRD and SEM were confirmed the presence of CS in PVA matrix. The vibrational properties and functional group assignment were studied. The thermal stability and electrochemical properties of chitosan/poly vinyl alcohol nanocomposite films were reported.

Development of a tannic acid- and silicate ion-functionalized PVA-starch composite hydrogel for in situ skeletal muscle repairing.

The repair capacity of skeletal muscle is severely diminished in massive skeletal muscle injuries accompanied by inflammation, resulting in muscle function loss and scar tissue formation. In the current work, we developed a tannic acid (TA)- and silicate ion-functionalized tissue adhesive poly(vinyl alcohol) (PVA)-starch composite hydrogel, referred to as PSTS (PVA-starch-TA-SiO32-). It was formed based on the hydrogen bonding of TA to organic polymers, as well as silicate-TA ligand interaction. PSTS could be gelatinized in minutes at room temperature with crosslinked network formation, making it applicable for injection. Further investigations revealed that PSTS had skeletal muscle-comparable conductivity and modulus to act as a temporary platform for muscle repairing. Moreover, PSTS could release TA and silicate ions in situ to inhibit bacterial growth, induce vascularization, and reduce oxidation, paving the way to the possibility of creating a favorable microenvironment for skeletal muscle regeneration and tissue fibrosis control. The in vivo model confirmed that PSTS could enhance muscle fiber regeneration and myotube formation, as well as reduce infection and inflammation risk. These findings thereby implied the great potential of PSTS in the treatment of formidable skeletal muscle injuries.

Influence of PVA resin and cross-linking agent on the structure and properties of semi-refined carrageenan-based packaging films

For the high content of carrageenan in some seaweed and the low cost and easy availability of semi refined carrageenan (SRC), SRC resin powder was selected as our research object. Due to its water solubility, a solution casting method was adopted to form film, hoping to prepare food packaging materials that partially replace petroleum based resin. The pure SRC resin casting film is very brittle and cannot be formed. Therefore, 40wt% glycerol was added to the formula to plasticize and improve the flexibility and demoulding ability of SRC. The plasticized SRC film still has limitations. Soluble petroleum based polymer poly(vinyl alcohol) (PVA) resin was used as a blending modifier, cinnamaldehyde (CIN) as a crosslinking agent for acetal reaction with hydroxyl groups, boric acid (BA) as a provider of acidic environment and an auxiliary agent for generating partial hydrogen bonds with hydroxyl groups. Eight experimental research formulas were designed and FTIR, XRD, thermodynamic properties and mechanical properties of the modified films were analyzed. Both microscopic and macroscopic analyses have shown that under the acidic conditions of BA, CIN undergoes an acetal reaction with SRC and PVA, therefore mass ratio of the formula that SRC/glycerol/PVA/CIN/BA is 100/40/33.3/10/10, the film has the best tensile strength of 34.85Mpa, higher than that of other films. It has been proven that CIN does indeed act as a crosslinking agent in the formula, forming a network structure that enhances it.

Selective ion migration in a polyelectrolyte driving a high-performance flexible moisture-electric generator.

We propose a novel moisture-electric generator that utilizes the unique properties of a blended poly(4-styrene sulfonic acid) and poly(vinyl alcohol) with phytic acid by screen printing and scrape coating, achieving an impressive open-circuit voltage of 0.88 V from ambient humidity. This innovative design significantly enhances ion transport, moisture adsorption, and flexibility, making a marked improvement in converting environmental humidity to electrical energy.

Boric acid-crosslinked poly(vinyl alcohol): biodegradable, biocompatible, robust, and high-barrier paper coating

The boric acid-crosslinked polyvinyl alcohol coating on paper remarkably improves barrier properties and mechanical robustness without compromising biodegradability and biocompatibility, a green advance in sustainable packaging.

Graphitic C3N4 incorporated chitosan-poly(vinyl alcohol) blend nanocomposites for the removal of Cu(II) and Cr(VI) ions from aqueous solutions

Graphitic C3N4 incorporated chitosan-poly(vinyl alcohol) blend nanocomposites for the removal of Cu(II) and Cr(VI) ions from aqueous solutions

Influence of Chemical Nature of Citric and Tartaric Acids on Reaction Time of the Crosslinking of Polyvinyl Alcohol Hydrogels.

Poly(vinyl alcohol) (PVOH) is a water-soluble polymer having a hydroxyl group as a functional group contributing to excellent membrane-forming and mechanical performance. PVOH is obtained by the hydrolysis of polyvinyl acetate, and its physical properties are affected by its degree of hydrolysis, whether, partial or complete. In this study, PVOH hydrogels were synthesized by a solution under stirring and heating techniques with citric (AC) and tartaric acids (AT) crosslinker agents, with different time reactions of 20 min.; 1; 2, and 3 h were investigated. These samples were characterized by the kinetics of water uptake, gel fraction, thermal analysis, and physical-chemical analysis, and their structure was elucidated. The results obtained have shown chemical modification by organic acids and improved the properties to good thermal stability and swelling to AT hydrogels up to 900% water uptake. In the gel fraction, the samples' esterification was shown and verified by FTIR spectra. To AC hydrogels the chemical modification was low due to the steric hindrance, which caused disintegration of the hydrogel in swelling and gel fraction test, but with absorption in the moisture test performed. The incorporation and effects of citric and tartaric acids enable the development of new hydrogel systems, with specific properties.

SERS detection of dopamine using metal-chelated Ag nanoshell.

As the concentrations of different neurotransmitters can indicate the presence of certain disorders affecting brain functions, quantitative analyses of neurotransmitters have attracted increasing attention in various fields. Surface-enhanced Raman scattering (SERS) spectroscopy is an outstanding spectroscopic analytical tool that enables detection at the single molecule level with high specificity. As local field enhancement of surface plasmon is effective within nanometers, active interaction between SERS-active noble metals (gold and silver) and analyte molecules enhances the molecular detection capacity of SERS. However, neurotransmitters and noble metal nanoparticles are often not affinitive, because neurotransmitters generally have a hydroxyl group rather than a thiol group. As a result, the interaction between the two typically remains inactive, which makes detection more difficult. To overcome this limitation, in the present work we utilized metal-chelation to attract dopamine, a neurotransmitter molecule, close to the surface of silver nanoparticles. AgNS was capped with poly(vinyl alcohol) (PVA) and sequentially integrated with copper ion to bind dopamine in the form of chelate bonding between dopamine and copper. The PVA linked AgNS and metal ions through a coordinate bond between hydroxyl groups and metal ions. This metal-chelation-functionalized nanoprobe allowed us to stably detect dopamine in aqueous solution at a concentration of less than 10-6 M. Therefore, this method provides a convenient and easy-to-prepare option for the effective detection of dopamine, thus meaning it has the potential to be applied to other neurotransmitters.

Multi-colour room-temperature phosphorescence from fused-ring compounds for dynamic anti-counterfeiting applications.

We present a facile strategy to achieve purely organic multi-colour room-temperature phosphorescence (RTP) films by doping typical fused-ring compounds into a poly(vinyl alcohol) matrix. Such RTP films demonstrate inherent RTP emission ranging from green to red with a long lifetime and high quantum yield (QY) (lifetime: ∼0.56 ms, QY: ∼35.4%). We further exploit such high-performance RTP films for dynamic information encryption.

Microwave-assisted synthesis and characterizations of nanosized copper ferrite and barium titanate for antimicrobial applications

Science and technology of nanosized bimetallic oxide nanomaterials records the various properties and applications. Especially biomedical applications are viewed in particular due to its nanosized particle size. The present experimentation is reporting the microwave-assisted synthesis of nanosized bimetallic oxides like copper ferrite (CuFe2O4) and barium titanate (BaTiO3) by solid state combustion route using poly (vinyl alcohol) (PVA) as a fuel. The structural and morphological characterizations of the bimetallic oxide nanomaterials are performed out by X-ray diffraction (XRD) and scanning electron micrograph (SEM) tools respectively. These analyses report the crystalline nature of both samples. EDX spectral study is also undertaken to know the existence of different metals in the above-mentioned samples. Bonding nature of the bimetallic oxide samples were readied by Fourier transfer infrared (FT-IR) instrumentation. The study reviewed the varied vibrational modes confirms the phase formation of the samples. UV-Vis and thermal study of these bimetallic oxide samples are also studied extensively to know the thermal and absorption behavior respectively. TGA of both the samples are traced and are showing decomposition at rapid rate. In addition, the maximum absorption peaks due to π - π* transition confirms the sample formation. Antimicrobial activity of the prepared oxide samples was studied for antibacterial and antifungal behavior. Both samples showing considerable activity against various bacteria and fungi.

Comparison between Onyx and coil embolization for persistent type 2 endoleaks after endovascular aneurysm repair.

Type 2 endoleaks (T2EL) are the most common form of endoleaks after endovascular aneurysm repair (EVAR). Several studies on the feasibility of embolization using ethylene vinyl alcohol copolymer (Onyx, Medtronic) for T2EL have been reported. The purpose of this study was to compare coil and Onyx embolization for T2EL treatment after EVAR. Between August 2005 and July 2022, 46 patients underwent endovascular embolization for treatment of T2EL (15 Onyx and 31 coils). The primary endpoint was endoleaks resolution or significant aneurysm sac growth of >5 mm in maximal diameter after T2EL embolization. In addition, periprocedural factors, reintervention, sac rupture, and survival analysis were assessed. The follow-up period after embolization was significantly shorter in the Onyx group (11.6 months vs. 34.7 months, P = 0.016), and there was no difference in aneurysm sac growth rate between both groups (20.0% vs. 51.6%; P = 0.472, log-rank test). However, cases with multiple endoleak origins tended to be treated with Onyx (P = 0.002). When applying Onyx, there was no significant difference in results between the transarterial and translumbar approaches. There appears to be no significant difference in the results of Onyx and coil embolization for T2EL treatment, although it is difficult to evaluate effectiveness due to the small number of cases and short follow-up period. However, in cases of multiple origin endoleaks or when the transarterial approach is not feasible, the Onyx by translumbar approach may be a more effective method.

Hierarchically Structured Hydrogel Composites with Ultra‐High Conductivity for Soft Electronics

AbstractConductive hydrogels possessing high conductivity, stretchability, and biocompatibility are promising materials for underwater devices and bioelectronics. However, typical hydrogels often exhibit low electrical conductivity, which is insufficient for applications requiring high electronic communication. A common approach to increase hydrogel conductivity is to introduce conductive fillers; however, this usually implies a partial sacrifice of stretchability, biocompatibility, and water content. In addition, the electrical properties of hydrogels tend to be unstable due to rehydration in aqueous environments. In this study, a conductive hydrogel composite is fabricated from silver nanowires (AgNWs) and poly(vinyl alcohol) (PVA) employing a synergistic method of freezing and salting‐out treatments. This combined method constructs a hierarchical hydrogel structure and increases the local concentration of AgNWs by inducing continuous phase separation. The resultant conductive hydrogel composites exhibit ultra‐high electrical conductivity (≈1739 S cm−1) and electrical stability in aqueous environments while maintaining high water content (≈87%), stretchability (≈480%), and excellent biocompatibility. To illustrate the capabilities of the conductive hydrogel composites, they are applied to bionic sharks, underwater soft circuitry, and electrocardiogram electrodes.

Preparation and characterization of glutathione loaded polyvinyl alcohol electrospun nanofibers

Reduced glutathione, or L-glutathione, is a tripeptide protein that occurs naturally in almost all cells of the human body. It is an antioxidant and plays a significant role in neutralizing oxidative stress. Oxidative stress is responsible for promoting many diseases and abnormalities in the body. This antioxidant decreases with time, and resulting in a number of disorders. To overcome these issues, experts recommend taking glutathione supplements. This study was aimed to design glutathione-loaded polyvinyl alcohol nanofibers, considering the properties of nanofibers that could be used as glutathione supplements to improve the deficiency of glutathione in the human body. With the electrospinning technique, poly (vinyl alcohol) loaded glutathione nanofibers were designed. The prepared nanofibers were characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Ultraviolet-Visible Spectroscopy (UV–Vis) techniques. The antioxidant activity of the nanofibers was also determined; the activity indicated the eradication of free radicals.

Poly (vinyl alcohol)-gelatin-sericin copolymerized film fortified with vesicle-entrapped demethoxycurcumin/bisdemethoxycurcumin for improved stability, antibacterial, anti-inflammatory, and skin tissue regeneration

Vesicle delivery carriers, used to stabilize hydrophobic drugs, are characterized by the propensity to aggregate, and fuse, limiting its applications. Fortifying vesicle-entrapped drugs within a biodegradable polymeric film constitutes a promising solution. In this study, biodegradable poly (vinyl alcohol) copolymerized with gelatin-sericin film and integrated alongside vesicle-entrapped demethoxycurcumin (DMC) or bisdemethoxycurcumin (BDMC) was developed, extensively characterized for improve efficacy, and compared. Vesicle-entrapped DMC or BDMC was spherical in shape with no changes in size, zeta-potential, and morphology after storing at 4 °C for 30 days. Antibacterial activity of vesicle-entrapped DMC formulations against Acinetobacter baumannii and Staphylococcus epidermidis was more effective than that of its free form. DMC and BDMC demonstrated dose dependent reduction in lipopolysaccharides (LPS)-induced nitric oxide (NO) levels either in free or in entrapped form. Moreover, vesicle-entrapped DMC/BDMC suppressed NO production at lower concentrations, compared with that of their free form and significantly improved the viability of RAW264.7 and HaCaT cells. Furthermore, functionalized film with vesicle-entrapped DMC/BDMC demonstrated excellent radical scavenging, biocompatibility, and cell migration efficacy. Thus, incorporating vesicle, entrapped DMC/BDMC within biodegradable polymeric film may comprised a promising strategy for improving stability, wound healing, and inflammation attenuation efficacy.

Effect of pH on the Poly(acrylic acid)/Poly(vinyl alcohol)/Lysozyme Complexes Formation.

The interactions between poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), and lysozyme (Lys) in an aqueous environment at pHs of 2, 4, and 7.4 were discussed considering the experimental data obtained by turbidimetry, electrokinetic and rheological measurements, and FTIR analysis. It was found that the increase in PAA amount reduces the coacervation zone by shifting the critical pHcr1to higher values while the critical pHcr2 remains unchanged. The coacervation zone extended from 3.1-4.2 to 2.9-4.7 increasing the Lys concentration from 0.2% to 0.5%. The zeta potential measurements showed that the PAA-PVA-Lys mixture in water is the most stable in the pH range of 4.5-8. Zero shear viscosity exhibited deviations from additivity at both investigated pHs, and a maximum value corresponding to a maximum hydrodynamic volume was revealed at PAA weight fractions of 0.4 and 0.5 for pHs of 4 and 7.4, respectively. The binding affinity to Lys of PAA, established by molecular dynamics simulation, was slightly higher than that of PVA. The more stable complex was PAA-Lys formed in a very acidic environment; for that, a binding affinity of -7.1 kcal/mol was determined.

Low-cost and simple fabrication of micro-mask/micro-channels on different substrates based on water-soluble fiber poly (vinyl alcohol) (PVA)

Here we report an approach to fabricate micro-mask/micro-channels using water-soluble fiber poly (vinyl alcohol) (PVA). The scheme is a simple, environmentally friendly, and low-cost technology, that can realize the preparation of micro-mask/micro-channels on different substrates. Scanning electron microscope (SEM) and optical microscope (OM) are used to observe surface morphology and measured fiber diameter. We showed that a variety of micro-mask/micro-channels can be easily controlled by changing the swelling temperature and time of the PVA fiber. The swelling temperature was varied from 25 °C to 50 °C, the diameter of the fiber increased by 9.5 μm, and the diameter and volume swelling rates reached 59.38% and 154%, respectively. Meanwhile, with the increase in swelling time, the diameter and volume swelling rate showed the same increasing trend. Additionally, we used the PVA fiber as a micro-mask to prepare the micro-channel on the WSe2 surface and verified the feasibility of the PVA fiber to prepare micro-mask/micro-channels by testing the electrical properties of the WSe2 sample. Finally, we also verified the feasibility of the above methods to fabricate micro-mask/micro-channels on different substrates such as conductive fibers, PDMS, and WSe2/SiO2Si, and proposed to realize nano-scale patterning through direct electrospinning. Therefore, it is expected to be more widely promoted in the future.

Low-Viscous, Dilute Phase Adhesive from Dense Polyphenolic Coacervates of Poly(vinyl alcohol) and Tannic acid.

This study explores a polyphenolic coacervate, named VATA, formed by poly(vinyl alcohol) (PVA) and tannic acid (TA). Distinct from conventional studies that have focused on the bottom, dense phase of coacervates, this research emphasizes the top, dilute phase, low-viscous coacervate liquid termed liquid-VATA (l-VATA). Due to TA's capability of intermolecular association as well as adhesiveness, phenomena not typically observed in the upper dilute phase of standard polyelectrolyte-based coacervates are revealed. At first glance, the dilute phase l-VATA coacervate resembles a water-like, low-viscous mixture solution of PVA, TA, and PVA/TA complexes. However, analysis shows that nearly all of the TA molecules associate with PVA chains, forming PVA/TA complexes. Furthermore, supraparticular association was observed between PVA/TA complex nanoparticles upon applying external shear force. A broad survey of shear rate and strain showed that the solution exhibited sequential shear-thickening, followed by shear-thinning behavior. The water-like, low viscosity of l-VATA unexpectedly reveals robust adhesiveness and thus able to lift an entire mouse using just a single human hair strand. Even in cases of failure, no interfacial failure was detected between mouse and human hair. In addition to enabling hair-to-hair bonding, our study also showcases the efficacy of l-VATA in facilitating hair-to-skin adhesion. The results illustrate how the lower viscosity of l-VATA can be exploited for a wide range of industrial and cosmetic applications, allowing the formulation of thin, uniform adhesive layers, something unachievable with the dense, viscous VATA glue. Thus, this study highlights the importance of investigating the top dilute phase of coacervates, shedding light on an area often underestimated compared to the bottom dense phase reported in prevalent coacervate studies.