Crosslinked Poly Vinyl Alcohol Research Articles

Charge-patterned nanofiltration membranes with polystyrene sulfonate particles and polyethyleneimine in cross-linked polyvinyl alcohol

Removing salinity has always been a challenge for wastewater treatment. Utilizing nanofiltration (NF) membranes is a promising approach. However, currently available NF membranes are less effective in monovalent salt removal. In this study, work toward the initial aim of fabricating charge mosaic membranes led to charge-patterned NF-selective films on polyether sulfone (PES) or polyacrylonitrile (PAN) support membranes, with similar rejection for mono- and divalent salts. The membranes were fabricated by a two-step layer assembly of first negatively charged polystyrene sulfonate (PSS) particles immobilized in a polyvinyl alcohol (PVA) layer, followed by coating a positively charged polyethyleneimine (PEI) layer. Both PVA and PEI were crosslinked using glutaraldehyde that had initially been impregnated into the support membrane. The type of support membrane, nanoparticle, PVA, and PEI concentrations during fabrication, as well as feed pH and salt concentration, play significant roles in separation performance of obtained composite membranes. Charge-patterned NF membranes fabricated using 0.5 wt.% PVA and 0.05 wt.% PSS for assembly of the first layer followed by coating 0.5 wt.% PEI solution had even somewhat higher rejection for monovalent salt (NaCl; ∼82%) compared to multivalent salts (Na2SO4, MgSO4, and MgCl2; ∼74%), at a permeance of 5.5 LMH/bar on the PES and 3.1 LMH/bar on the PAN support membrane.

Processing physically crosslinked polyvinyl alcohol hydrogel into solid foams via freeze-drying: The role of hydrogel state

Processing hydrogels into solid foams or aerogels via freeze-drying broaden their applications. However, one challenge is its inherent processing instability, often leading to dimensional shrinkage and structural collapse of the resultant solid foams. To address this, our study investigated the role of hydrogel state in the solid foam formation. Specifically, polyvinyl alcohol (PVA) hydrogel, synthesized through repeated freeze-thaw (FT) cycles, was investigated. It was found that PVA concentration and FT cycles played a vital role; specifically, higher PVA concentration and more FT cycles negatively affected solid foam formation. These hydrogels exhibited an increase in hydrogel viscoelasticity and crystallizability of the most flexible chains, indicative of strong and denser network structure. We proposed that the final solid foam structure was determined by a balance between the volumetric expansion due to water-to-ice transition during freezing and the intense inter-polymeric chain attractions within the denser network during sublimation.

Tartaric Acid Cross-Linking Polyvinyl Alcohol as Degradable Separators for Rechargeable Lithium Ion Batteries.

The escalating focus on environmental concerns and the swift advancement of eco-friendly biodegradable batteries raises a pressing demand for enhanced material design in the battery field. The traditional polypropylene (PP) that is monopolistically utilized in the commercial LIBs is hard to recycle. In this work, we prepare a novel water degradable separators via the cross-linking of polyvinyl alcohol (PVA) and dibasic acid (tartaric acid, TA). Through the integration of non-solvent liquid-phase separation, we successfully produced a thermally stable PVA-TA membrane with tunable thickness and a high level of porosity. These specially engineered PVA-TA separators were implemented in LiFePO4 (LFP)|separator|Li cells, resulting in superior multiplicative performance and achieving a capacity of 88 mAh g-1 under 5 C. Additionally, the straightforward small molecule cross-linking technique significantly reduced the crystalline region of the polymer, thereby enhancing ionic conductivity. Notably, after cycling, the PVA-TA separators can be easily dissolved in 95 °C hot water, enabling its reutilization for the production of new PVA-TA separators. Therefore, this work introduces a novel concept to design green and sustainable separators for recyclable lithium batteries.

Detection of H2O2 and catalase on a paper-based flow sensor constructed with borate cross-linked PVA hydrogel

The detections of H2O2 and catalase play an important role in daily life. This study introduces a paper-based flow sensor that is specifically designed to detect H2O2 and catalase. The sensor utilizes a hydrogel composed of cross-linked 4-carboxyphenylboronic acid and polyvinyl alcohol. When H2O2 is in contact with the hydrogel, the B–C bonds of the hydrogel undergo a reactive process, causing decomposition of the hydrogel. The pH indicator strip enables the visual monitoring of the viscosity change that occurs during the gel-sol transition. The quantification of H2O2 is accomplished by assessing the proportion of water coverage on the pH indicator strip. The sensor shows a detection limit of 0.077 wt% and is applicable for the quantitative measurement of H2O2 in routinely used disinfectants. Furthermore, the presence of catalase is effectively identified and the detection of catalase in milk is successfully fulfilled. In summary, this work proposes a simple, user-friendly, label-free, and cost-effective method for constructing a paper-based flow sensor using borate cross-linked polyvinyl alcohol hydrogel, showing great potential for detecting H2O2 and catalase in various practical scenarios.

Tough and biodegradable C-lignin cross-linked polyvinyl alcohol supramolecular composite films with closed-looping recyclability

Catechyl lignin (C-lignin) is a unique natural biopolymer that is considered to be the best alternative to conventional lignin due to its linear homogeneous molecular structure. Based on the structural properties of C-lignin, the development of a new biodegradable plastic to replace traditional petroleum-based plastics is a sustainable route. However, the maximum filling fraction of lignin is required to achieve excellent biodegradability of lignin-based bio-plastics, yet resulting in decreased mechanical strength of composites. Herein, we report a novel strategy to fabricate a closed-loopling recyclability supramolecular composite films through casting and dry molding process of intermolecular covalent-noncovalent cross-linking networks with polyvinyl alcohol by the epoxidation of C-lignin. The intermolecular cross-linking mechanism analyses reveal that the resultant bio-material not only display improved mechanical properties (maximum tensile strength of 133.5 MPa and strain at break of 690.2 %), but also show UV-resistant, antimicrobial, thermally stable, and rapid biodegradable properties. Notably, the fabricated films demonstrate the characteristics of closed-loop recyclability, which paves a new way toward rational design of bioplastics using renewable lignin. These integrated properties make the lignin-based biocomposites a promising alternative to traditional plastics.

Cover Image, Volume 141, Issue 22

The cover image is based on the Research Article Development of crosslinked polyvinyl alcohol nanofibrous membrane for microplastic removal from water by Anandu Nair Gopakumar et al., https://doi.org/10.1002/app.55428image

Fine extraction of cellulose from corn straw and the application for eco-friendly packaging films enhanced with polyvinyl alcohol

Biomass materials substituting for petroleum-based polymers occupy an important position in achieving sustainable development. Cellulose, a typical biomass material, stands out as the primary choice for producing eco-friendly packaging materials. However, it is still a challenge to efficiently utilize cellulose from waste biomass materials in practice. Herein, cellulose-based films were prepared by pretreating waste corn straw, separating straw husk, straw pith and straw leaf, and extracting cellulose through alkali and sodium chlorite treatment to improve its mechanical properties using the cross-linked polyvinyl alcohol (PVA) method in this work. The prepared composite films were characterized by Fourier transform infrared spectrometer (FTIR), X-ray diffraction instrument (XRD), Scanning electron microscopy (SEM), Thermogravimetric (TG) and mechanical properties. The results indicated that corn straw husk exhibited the highest cellulose content of 31.67 wt%, and obtained husk cellulose had the highest crystallinity of 52.5 %. Compared to corn straw, the crystallinity of husk cellulose, pith cellulose and leaf cellulose increased by 19.5 %, 16.4 % and 44.1 %, respectively. Husk cellulose/PVA composite films were the most thermally stable, with a maximum weight loss temperature of 346.8 °C. In addition, the husk cellulose/PVA composite film had the best tensile strength of 37 MPa. Meanwhile, the composite films had good UV shielding, low water vapor transmission rate and biodegradability. Therefore, this work provides a fine utilization route of waste corn straw, and as-prepared cellulose based films have potential application in eco-friendly packaging materials.

Control of polymers’ amorphous-crystalline transition enables miniaturization and multifunctional integration for hydrogel bioelectronics

Soft bioelectronic devices exhibit motion-adaptive properties for neural interfaces to investigate complex neural circuits. Here, we develop a fabrication approach through the control of metamorphic polymers’ amorphous-crystalline transition to miniaturize and integrate multiple components into hydrogel bioelectronics. We attain an about 80% diameter reduction in chemically cross-linked polyvinyl alcohol hydrogel fibers in a fully hydrated state. This strategy allows regulation of hydrogel properties, including refractive index (1.37-1.40 at 480 nm), light transmission (>96%), stretchability (139-169%), bending stiffness (4.6 ± 1.4 N/m), and elastic modulus (2.8-9.3 MPa). To exploit the applications, we apply step-index hydrogel optical probes in the mouse ventral tegmental area, coupled with fiber photometry recordings and social behavioral assays. Additionally, we fabricate carbon nanotubes-PVA hydrogel microelectrodes by incorporating conductive nanomaterials in hydrogel for spontaneous neural activities recording. We enable simultaneous optogenetic stimulation and electrophysiological recordings of light-triggered neural activities in Channelrhodopsin-2 transgenic mice.

Insight into low-grade natural Linze palygorskite for composite particles preparation towards efficient wastewater treatment

Natural clay possesses advantages such as low cost and high adsorption capacity, rendering it a promising adsorbent for wastewater treatment. In this work, low-grade Linze palygorskite (LZ), comprising 20.5% palygorskite, was utilized as a representative material to synthesize polyvinylformal-LZ (PVFM-LZ) composite particles through cross-linking polyvinyl alcohol (PVA) with formaldehyde. The raw material ratio of LZ and PVA was maintained at a high level of 20:1. Meanwhile, high-purity montmorillonite (Mt) and palygorskite (Pal) were employed as raw materials to prepare PVFM-Mt and PVFM-Pal using the same method, enabling comparative analysis with PVFM-LZ. PVFM-LZ exhibited a notable adsorption capacity of 101.92 mg·g−1 for methylene blue, which was comparable to that of PVFM-Mt and PVFM-Pal. What’s more, owing to the tightly cross-linked network structure formed by PVFM, PVFM-LZ demonstrated minimal loss (2.53%) and swelling (8.0%) rates in water, facilitating easy separation and promoting recyclability. Even after six cycles, its adsorption efficiency remained above 85%. The structure, physicochemical properties and adsorption performance of the three composite particles were meticulously examined before and after adsorption. Kinetic, thermodynamic and isotherm adsorption models revealed that PVFM-LZ exhibited spontaneous surface-controlled monolayer adsorption behavior. The possible adsorption mechanisms included electrostatic interactions, hydrogen bonding, and intermolecular forces. This work may provide an experience for the adsorption application of low-grade natural clay in composite engineering.

Preparation of PVA/CNTs film with high stability and humidity sensitivity based on multiple process

Polyvinyl alcohol (PVA) is a polyhydroxylated water-soluble polymer with rapid response to water molecules in environment. In this paper, a humidity sensitive PVA film with both high stability and satisfactory humidity sensitivity were prepared based on multiple process, i.e., crosslinking, foaming, spin coating and composition with hydroxylated carbon nanotubes (CNTs). The crosslinking of PVA with formaldehyde enhances the stability of the film under cyclic test condition, which exhibits deviation ratio of 1.1 and 1.2 in response and recovery process respectively. The pore structure generated by foaming agent promotes the water vapor exchange efficiency and improve the humidity response and recovery performance. The spin coating speed significantly influences the pore structure and thickness of the prepared films. CNTs facilitate the dissociation of water molecule through hole carriers and hydroxyl groups to reduce the resistance of PVA/CNTs films and enlarge the humidity response range. The spin coating speed and CNTs content jointly determine the final foaming structure and film thickness. Based on the multiple methods, the obtained crosslinked open pore film exhibits satisfactory humidity sensitive properties with the response time of 48 s and equilibrium time of 296 s, which should have good application prospect.

Preparation and characterization of high barrier coating of citric acid crosslinked polyvinyl alcohol and nano-SiO2

Preparation and characterization of high barrier coating of citric acid crosslinked polyvinyl alcohol and nano-SiO2

Physically crosslinked polyvinyl alcohol, phytic acid and glycerol hydrogels for wearable sensors with biocompatibility, antimicrobial stability and anti-freezing

Portable, miniaturized, intelligent and flexible electronic devices are more and more widely used in life areas. Conductive hydrogels with remarkable ion transport capabilities and tunable mechanical properties could be emerging materials for sensing devices. However, most of conductive hydrogels do not have antimicrobial activity, leading to microbial infections for human. Herein, a hydrogel with noteworthy biocompatibility, antimicrobial stability, anti-freezing, and anti-fatigue properties was designed and developed by introducing polyvinyl alcohol, phytic acid, and glycerol. Phytic acid and PVA formed hydrogen bonds by physically cross-linking, improving the fatigue resistance and toughness of the hydrogel. The hydrogel exhibited bacteriostatic zone against for Escherichia coli as well as Bacillus subtilis, and displayed antibacterial stability within 7 days. Hydrogels appeared distinguished biocompatibility due to the absence of allergic reactions in mouse subcutaneous tissue within 14 days. Hydrogels as sensors could monitor deformational movements such as speech and joint bending. Thus, hydrogels have the potential to be used as antimicrobial materials in medical applications such as implantable sensors and clinical information interventions.

Highly transparent and flame‐retardant polyvinyl alcohol membranes crosslinked with 2‐methyl‐2,5‐dioxo‐1,2‐oxaphospholane

AbstractIn the present paper, crosslinked polyvinyl alcohol (PVA) membranes with high transparency and excellent flame retardancy were obtained by blending 2‐methyl‐2,5‐dioxo‐1,2‐oxaphospholane (OP) with a PVA water solution at the molecular scale. Fourier transform infrared spectrometry and differential scanning calorimetry were used to investigate the crosslinking reaction. The surface morphology and micromechanical assessments of the membrane were examined using nanoindentation. The limited oxygen index (LOI) and vertical flame microscale combustion calorimetry, thermogravimetric analysis, scanning electron microscopy (SEM), energy‐dispersive spectroscopy (EDS), and x‐ray photoelectron spectroscopy (XPS) were employed to evaluate the flame retardancy and reveal the corresponding mechanisms. It was found that OP reacted with PVA below 120°C. The crosslinked membranes have a rougher surface and higher hydrophilicity and lower hardness and modulus than pure PVA does. The crosslinked membranes exhibit enhanced flame retardancy and high transparency. The membrane passes the UL 94 V 0 rating with an LOI of 27.6% and achieves a transmittance of 90.2% when the OP content is 20 wt.%. The SEM, EDS, and XPS results demonstrate that the interaction between OP and PVA effectively promotes the formation of a continuous and stable char in the condensed phase.

Anti-freezing hydrogel regulated by ice-structuring proteins/cellulose nanofibers system as flexible sensor for winter sports

Conductive hydrogels are widely used as sensors in wearable devices. However, hydrogels cannot endure harsh low-temperature environments. Herein, a new regulatory system based on natural ice-structuring proteins (ISPs) and cellulose nanofibers (CNFs) is introduced into hydrogel network consisting of chemically crosslinked network of copolymerized acrylamide and 2-acrylamide-2-methylpropanesulfonic acid, and physically crosslinked polyvinyl alcohol chains, affording an anti-freezing hydrogel with high conductivity (2.63 S/m). These hydrogels show excellent adhesion behavior to various matrices (including aluminum, glass, pigskin, and plastic). Their mechanical properties are significantly improved with the increase in CNF content (tensile strength of 106.4 kPa, elastic modulus of 133.8 kPa). In addition, ISPs inhibit the growth of ice. This endows the hydrogels with anti-freezing property and allows them to maintain satisfactory mechanical properties, conductivity and sensing properties below zero degrees. Moreover, this hydrogel shows high sensitivity to tensile and compressive deformation (GF = 5.07 at 600–800 % strain). Therefore, it can be utilized to develop strain-type pressure sensors that can be attached directly to human skin for detecting various body motions accurately, reliably, and stably. This study proposes a simple strategy to improve the anti-freezing property of hydrogels, which provides new insights for developing flexible hydrogel electronic devices for application in winter sports.

Plastisols based on polyvinyl alcohol and their use for the production of children’s products

In this work, plastisol compositions have been developed for the production of plastic masses based on chemically cross-linked polyvinyl alcohol and polymer expanded microspheres for the production of air clay

Development of crosslinked polyvinyl alcohol nanofibrous membrane for microplastic removal from water

AbstractThis study presents the development of an innovative nanofibrous membrane to remove microplastics (MPs) from drinking water. This membrane exhibits additional functionality in removing lead (Pb), highlighting its promising potential for utilization as a point‐of‐use (POU) device. The polyvinyl alcohol (PVA) nanofibrous membranes are crosslinked using glutaraldehyde, and their efficiencies in the removal of MPs are evaluated. The results show that crosslinking the 7 and 10 wt% PVA nanofibers increases their average diameters to 330 and 581 nm, respectively, and enhances their surface area. The treatment efficiency of crosslinked PVA fibrous media is evaluated using polyethylene (PE) (5 μm ≤d ≤ 25 μm) and polystyrene (PS) MPs (d ≤ 1 μm). The filtration efficiencies of both 7 and 10 wt% c‐PVA nanofibrous media are found to be 99.8% ± 0.1% in the removal of PE MPs at pH 8. Further examination of the filtration efficiency in the removal of PS MPs shows that the highest removal efficiency achieved was 77.3% ± 1.4% at a pH of 6. Additionally, the lead removal efficiency of this fibrous membrane in flow‐through experiments is examined. Results show a pH‐dependent lead removal efficiency, in which the greatest efficiency of 69% is found at pH 6.

Conception of pH-sensitive calcium alginate/poly vinyl alcohol hydrogel beads for controlled oral curcumin delivery systems. Antibacterial and antioxidant properties

Curcumin, a bioactive compound derived from the rhizome of Curcuma longa, has gained widespread attention for its potential therapeutic properties, including anti-inflammatory, antioxidant and anticancer effects. However, its poor aqueous solubility, instability and limited bioavailability have hindered its clinical applications.New beads formulations based on sodium alginate biopolymer (SA) and poly vinyl alcohol (PVA) were successfully prepared and evaluated as a potential drug vehicle for extended release of curcumin (Cur). Pristine and curcumin loaded calcium alginate/poly vinyl alcohol beads (CA/PVA and CA/PVA/Cur) at different compositions of SA and PVA were prepared by an ionotropic gelation method of SA followed by two freeze-thawing (FT) cycles for further crosslinking of PVA. Characterization techniques, such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV–Visible spectroscopy, thermogravimetric analysis (TGA) and x-ray diffraction (XRD) were used to confirm the successful microencapsulation of curcumin within the CA/PVA microcapsules. Furthermore, the swelling of pristine beads, pH-sensitive properties and in vitro release studies of curcumin loaded beads were investigated at 37 °C in simulated gastric fluid (SGF), simulated intestinal fluid (SIF) and simulated colonic fluid (SCF). The effect of the polymer blend ratio, the encapsulation efficiency (EE %) of curcumin, the loading capacity (LC μg/mg), the sphericity factor (SF), the antioxidant activity of the elaborated beads and their antimicrobial properties against bacteria and fungi were just as much evaluated.The obtained results indicate that the swelling and the behavior of the developed beads were influenced by the pH of the test medium and the PVA content. The introduction of PVA into the SA matrix greatly enhanced the physicochemical properties, the encapsulation efficiency and the loading capacity of the elaborated microparticles. Results also suggested that the antioxidant activity of the loaded beads (CA/PVA/Cur) showed a higher DPPH radical scavenging activity while the bacterial and fungal strains proved sensitive to the different formulations used in the assay. Moreover, the important drug encapsulation efficiency and the sustainable drug release of these materials make them promising for the development of new drug carrier systems for colon targeting.

Modification of thermal and electrical characteristics of hybrid polymer nanocomposites through gamma irradiation for advanced applications

In this article, we present a straightforward in-situ approach for producing Ag NPs incorporated in graphene oxide (GO) blended with glutaraldehyde (GA) cross-linked polyvinyl alcohol (PVA) matrix. Samples are γ-irradiated by doses of 2, 5, and 10 kGy and in comparison with the pristine films, the thermal conductivity (‘k’) and effusivity are measured. ‘k’ decreases with irradiation doses up to 5 kGy and further increase in the dosage results increase in ‘k’. We performed FDTD modeling to verify the effect of polarization and periodicity on the absorptivity and emissivity spectra that are correlated to the ‘k’ and effusivity, empirically. Hence, we can confess that the structural properties of the prepared hybrid nanocomposite are manipulated by γ-irradiation. This attests that the PVA/GO-Ag/GA nanocomposite is radiation-sensitive and could be employed for thermal management systems. Moreover, their strong electrical insulation, as the measured dc conductivity of the γ-irradiated samples is found to be in the range of 2.66 × 10−8–4.319 × 10−7 Sm−1, which is below the percolation threshold of 1.0 × 10−6 Sm−1, demonstrates that they are excellent candidates for the use of thermal management materials. The low ‘k’ values allow us to use this promising material as thermal insulating substrates in microsensors and microsystems. They are also great choices for usage as wire and cable insulation in nuclear reactors due to their superior electrical insulation.Graphical

Effect of epichlorohydrin treatment on the coating process and performance of high-barrier paper packaging

The fabrication of coated papers using hydrophilic and biodegradable polymers is important for developing sustainable packaging materials with high barrier and superior mechanical properties. However, water, which is used as the solvent in the paper coating process using hydrophilic polymers, deforms the shape of the paper and deteriorates performance. Therefore, we propose a new coating process that treats Kraft paper (KP) with epichlorohydrin (ECH) as a binder before the coating process. Crosslinked polyvinyl alcohol is coated on the ECH-treated KP using a solution casting method. ECH maintains the shape of the paper and improves coating uniformity; significantly enhances interfacial interactions, which increases barrier properties and sealing strength; and extends the shelf life of biscuits by reducing oxygen and moisture permeability. An ecotoxicity test using Lolium multiflorum demonstrates an insignificant phytotoxicity level for the as-prepared coated papers. Thus, ECH-treated KP is a potential candidate for high-barrier food packaging.

Light and Heat-Driven Flexible Solid Supramolecular Polymer Displaying Phosphorescence and Reversible Photochromism.

Herein, a type of light- and heat-driven flexible supramolecular polymer with reversibly long-lived phosphorescence and photochromism is constructed from acrylamide copolymers with 4-phenylpyridinium derivatives containing a cyano group (P-CN, P-oM, P-mM), sulfobutylether-β-cyclodextrin (SBCD), and polyvinyl alcohol (PVA). Compared to their parent solid polymers, these flexible supramolecules based on the non-covalent cross-linking of copolymers, SBCD, and PVA efficiently boost the phosphorescence lifetimes (723.0ms for P-CN, 623.0ms for P-oM, 945.8ms for P-mM) through electrostatic interaction and hydrogen bonds. The phosphorescence intensity/lifetime, showing excellent responsiveness to light and heat, sharply decreased after irradiation with a 275nm flashlight or sunlight and gradually recovered through heating. This is accompanied by the occurrence and fading of visible photochromism, manifesting as dark green for P-CN and pink for P-oM and P-mM. These reversible photochromism and phosphorescence behaviors are mainly attributed to the generation and disappearance of organic radicals in the 4-phenylpyridinium derivatives with a cyano group, which can guide tunable luminescence and photochromism.