Crosslinked Poly Vinyl Alcohol Research Articles

Crosslinking of polyvinyl alcohol with di, tri, and tetracarboxylic acids: an experimental investigation

Crosslinking of polyvinyl alcohol with di, tri, and tetracarboxylic acids: an experimental investigation

Enhancing the performance of nanostructured PVA/SA scaffolds through incorporation of macromolecules: From synergistic effects to advanced multifunctionalities

The increasing use of biomaterial scaffolds in tissue engineering applications demands a comprehensive understanding and precise control of their overall properties. This work analyzes the synergy of naturally occurring biological macromolecules on the swelling, and thermal and mechanical properties of ionically crosslinked polyvinyl alcohol (PVA)/sodium alginate (SA) fibrous scaffolds. The presence of collagen (COL) or hyaluronic acid (HA) contributed not only to increasing the hydrogen-bond density but also to induce the crystalline PVA phase formation. Consequently, the swelling, thermal degradation, elastic modulus, and nanohardness of the scaffolds were significantly enhanced. By considering COL and HA the relevance in diverse cellular processes and tissue functions, the PVA-scaffolds here introduced are promising materials by providing advanced multifunctionalities.

Gel beads prepared by polyvinyl alcohol cross-linking with phytic acid and Fe as novel microbial carriers for simultaneous partial nitrification, anammox and denitrification

Enhancing the stability of biomass and ensuring a stable activity of anaerobic ammonia oxidizing bacteria are crucial for successful operation of the simultaneous partial nitrification, Anammox, and denitrification (SNAD) process. In this study, gel beads of polyvinyl alcohol/phytic acid (PVA/PA) and polyvinyl alcohol/phytic acid/Fe (PVA/PA/Fe) were prepared as innovative bio-carriers. Theoretical simulations and analyses revealed that these carriers are predominantly connected via hydrogen and borate bonds, with PVA/PA/Fe also featuring metal coordination bonds. The total nitrogen removal efficiency of reactors with PVA/PA/Fe and PVA/PA increased by 13.5 % and 9.0 %, respectively, compared to reactor without carriers. The iron-enriched PVA/PA/Fe carriers significantly improve SNAD by promoting Anammox, Feammox, and nitrate-dependent Fe2+ oxidation reactions, leading to faster nitrogen conversion and higher nitrogen removal rate than reactor without carriers and with PVA/PA. Using of PVA/PA and PVA/PA/Fe gel beads as bio-carriers offers benefits to the SNAD process, including cost-effective and low carbon requirement.

Coal tar pitch porous carbon-based bimolecular crosslinked hydrogel evaporator for solar-driven efficient water purification

Hydrogel evaporators have been widely used in solar-driven interfacial water evaporation due to their good thermal insulation, strong hydrophilicity, and rich internal pores. However, the occlusion pores in the hydrogel with a single molecule chain not only limit water transportation but also lead to serious salt crystallization. Hence, we developed a hydrogel evaporator (NSC-PVA/8CMC) with an abundant and open pore structure by cross-linking polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC). In which, the low-cost amorphous coal tar pitch porous carbon (NSC) is used to absorb light and improve light-to-heat conversion. The porous structure and thermal insulation (0.37 W m−1 K−1) of NSC-PVA/8CMC are conducive to excellent light absorption (≈99.02 %) and minimizing heat loss, finally leading to excellent photothermal conversion (1.44 kg m−2 h−1, 72.96 %, 1 sun). More significantly, NSC-PVA/8CMC with a strong desalination capacity can provide a self-purifying performance in seawater and brackish water. At the same time, the innovative attempt to use coal tar pitch as the photothermal conversion material has expanded the application scope of coal tar pitch.

Engineering the nanozyme hydrogel beads by polyvinyl alcohol/chitosan encapsulation with recyclable and sustainable catalytic activity for visual analysis of hydrogen peroxide

BackgroundHydrogen peroxide (H2O2) plays a vital role in human health and have been regarded as a crucial analyte in metabolic processes, redox transformations, foods research and medical fields. Especially, the long-time and excessive digestion of H2O2 may even cause severe diseases. Although conventional instrumental methods and nanozymes-based colorimetric methods have been developed to accomplish the quantitative analysis of H2O2, the drawbacks of instrument dependence, cost-effectiveness, short lifespan, non-portable and unsustainable detection efficacies will limit their applications in different detection scenarios. ResultsHerein, to address these challenges, we have proposed a novel strategy for nanozyme (RuO2) hydrogel preparation by the solid support from cross-linked polyvinyl alcohol (PVA) and chitosan (CS) to both inherit the dominant peroxidase-like (POD) activity and protect the RuO2 from losing efficacies. Taking advantages from the hydrogel, the encapsulated RuO2 were further prepared as the regularly spherical beads (PCRO) to exhibit the sustainable, recyclable, and robust catalysis. Moreover, the intrinsic color interferences which originated from RuO2 can be avoided by the encapsulation strategy to promote the detection accuracy. Meanwhile, the high mechanical strength of PCRO shows the high stability, reproducibility, and cyclic catalysis to achieve the recyclable detection performance and long lifetime storage (40 days), which enables the sensitively detection of H2O2 with the detection limit as lower to 15 μM and the wide detection linear range from 0.025 to 1.0 mM. SignificanceOn the basis of the unique properties, PCRO has been further adopted to construct a smartphone detection platform to realize the instrument-free and visual analysis of H2O2 in multi-types of milk and real water samples through capturing, processing, and analyzing the RGB values from the colorimetric photographs. Therefore, PCRO with the advanced detection efficacies holds the great potential in achieving the portable and on-site analysis of targets-of-interest.

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.

Development of novel proton exchange membranes based on cross-linked polyvinyl alcohol (PVA)/5-sulfosalicylic acid (SSCA) for fuel cell applications

The proton-conducting and methanol permeation behaviors of polymeric electrolyte membranes (PEMs), as well as the expensive nature of direct methanol fuel cell (DMFC) components, pose major concerns in DMFC performance and commercialization. As a result, this research aimed to develop low-cost polyelectrolyte membranes based on cross-linked poly(vinyl alcohol)/5-sulfosalicylic acid dehydrate (PVA/SSCA) composite. Chemical cross-linkers and modifiers offer the essential chemical and mechanical stability of the developed membranes for usage as polyelectrolyte membranes (PEMs). The manufactured composite proton exchange membranes provide several benefits, including significant thermal, chemical, and mechanical stability. The results revealed that extending the SSCA molar concentration increased IEC outcomes of the synthesized membranes, reaching an elevated level of (3.31 meq g−1) compared to (0.91 meq g−1) for the Nafion 117 membrane. The proton conductivity of a composite membrane (102 μm thick) measured by impedance spectroscopy was relatively (0.078 S cm−1) and found comparable to other PVA-based composite membranes reported in the literature. Other key parameters, such as methanol permeability, were measured for constructed composite proton exchange membranes (2.52 × 10–7 cm2 s−1), which were much lower than Nafion 117 (3.39 × 10–6 cm2 s−1). The Fourier transform infrared (FT-IR), Raman scattering spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, elemental analysis, and thermal gravimetric analysis (TGA) were among the techniques used to characterize the synthesized membranes. These characterizations confirm the structural interaction between the membrane components’ crystalline nature, and no signs of phase separation or cracks were found; surface morphology and good membrane homogeneity, elemental analysis, and the membranes’ thermal stability (up to 290 °C). The membranes were also mechanically characterized using a universal testing machine (UTM), which revealed good mechanical stability. The findings demonstrate that a low-cost proton exchange membrane could potentially be synthesized for DMFC applications.

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.

Ionic Interactions of NaCl in Aqueous Polyvinyl Alcohol and Cross-Linked Polyvinyl Alcohol with Glutaraldehyde

Ionic Interactions of NaCl in Aqueous Polyvinyl Alcohol and Cross-Linked Polyvinyl Alcohol with Glutaraldehyde

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.