Introducing Poly Vinyl Alcohol Research Articles

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.

Antimicrobial and anti-freezing conductive hydrogels driven by quaternary ammonium chitosan salt for flexible strain sensors

Conductive hydrogels have great development prospects in the field of flexible strain sensors due to the unique characteristics of sufficient flexibility, comfort and functional diversification. However, long-term direct contact between hydrogel sensors and human skin can cause the phenomenon of bacterial infection, which accelerates the replaceable frequency of hydrogel wearable sensors, hindering the application of hydrogel wearable sensors. Here, the hydrogel with distinguished antibacterial, biocompatibility, frost resistance, water retention and toughness were designed and manufactured by a freeze–thaw method introducing polyvinyl alcohol, quaternary ammonium chitosan salt, polyhexamethylene biguanide hydrochloride, glycerin and lithium chloride. The hydrogel maintains remarkable tensile properties and fatigue resistance in the range from 25 °C to −20 °C, expanding the application of hydrogels as sensors. Meanwhile, the hydrogel was resistant to E. coli and Bacillus subtilis and could be preserved in mice for 14 days. As a result, the hydrogel sensors could be used to detect human movement in real time, such as finger bending, frowning, speaking and other movements. Therefore, the design of the hydrogel provides a simple research idea for implantable sensing devices.

Properties enhancement of magnesium phosphate cement by cross-linked polyvinyl alcohol

A novel ceramic composite has been obtained by introducing polyvinyl alcohol in magnesium-based chemically-bonded ceramics and exploiting the cross-link reaction with glutaraldehyde during setting. The properties of the obtained material and the interaction of the polymer with the cement reaction have been investigated. Several beneficial effects were observed. Namely, an extension of the working time, a reduction in the water sensitivity, a decrease in the rate of the heat evolution during hardening. The latter has been ascribed to the intervention of surface adsorption processes, which hindered the dissolution of MgO, as well as the nucleation and growth of the magnesium phosphate products, in concert with the film forming ability of the polymer. Thanks to the complementarity of their mechanical properties, the cement and the additive operated in a synergistic fashion, allowing for the obtainment of a material possessing higher strength and better elastic properties. Three-dimensional quantitative image analysis from synchrotron X-ray microcomputed tomography evidenced the development of a more compact microstructure, comprising a higher number of crystals of smaller size. As a consequence, the pore network exhibited a higher fraction of small pores and lower pore connectivity. These characteristics contributed to hinder the water absorption, as confirmed by the fluid transport simulations within the volume. The observed correlation between the solution pH and the polymer cross-link density offers the way to effectively modulate the material performance by acting on the chemical environment thanks to its compatibility with the cross-link reaction.

Stretchable, Antifreezing, Non‐Drying, and Fast‐Response Sensors Based on Cellulose Nanocomposite Hydrogels for Signal Detection

AbstractConductive hydrogels have received widespread attention in the applications of biosensors, human–machine interface, and health recording electrodes. Herein, the conductive hydrogels integrated with antifreezing, water retention, reusable, and sensing performances are fabricated by introducing polyvinyl alcohol, cellulose nanofibril, MXene nanosheets, and glycerol. The as‐prepared hydrogels present prominent electrical conductivity (2.58 mS cm−1) and flexibility even at −18 °C. In addition, the hydrogels have favorable water retention performance and can reuse after heating and cooling. When used as sensors, the hydrogels illustrate high sensitivity (gauge factor of 2.30), fast response time (0.165 s), wide working strain range (559%), favorable linearity (R2 = 0.999), and wide operating temperature range (−18 to 60 °C). The hydrogels can detect not only large strains of 10–200%, but also small strains of 1–5%, making them promising candidates for wearable sensors to monitor large and subtle movements.

Facile synthesis of novel porous graphene-like carbon hydrogel for highly efficient recovery of precious metal and removal of organic dye

New strategies for adsorbing environmental pollutants such as Ag+ and organic dyes are still in urgent need. Based on this, we developed a highly efficient adsorbent, porous graphene-like carbon (PGC), by a simple catalysis process. A three dimensional porous graphene-like carbon hydrogel (3D-PGCH) was further obtained by introducing polyvinyl alcohol (PVA) and fully cross-linked via freeze-drying. The 3D-PGCH had a high adsorption capacity for Ag+ with an adsorption value of 234.32 mg g−1 at pH 4 and 303 K. Its active ingredient PGC exhibited excellent adsorbing effect on methylene blue (MB), and the maximum adsorption was up to 13381.62 mg g−1, about 32 times higher than that of using single PGC. Moreover, the adsorption-desorption experiment reflected a good recyclability of 3D-PGCH, whose adsorption capacity remained a high level after four cycle experiments. This study provides a positive choice for resource conservation and wastewater remediation.

Mechanistic Approach for Reducing the Thickness of Asphalt Layer Incorporating Steel Slag Aggregate

This study aimed to evaluate the possibility of reducing the thickness of asphalt layer as a novel solution for the high density of asphalt layer incorporated with steel slag aggregate, which increase the cost of transportation. Mechanistic-Empirical Pavement Design (MEPDG) approach was employed to evaluate the benefits of introducing polyvinyl alcohol fiber in terms of reducing the thickness of asphalt layer as well as the extension service life of asphalt layer. On the other hand, the correlation between creep strain slope (CSS) and secant creep stiffness modulus (SCSM) were assessed to provide a better evaluation and understanding concerning of the outputs of the dynamic creep test. The findings of this study showed that introducing polyvinyl alcohol fiber into the mixtures at the optimum content (0.5 kg/ton) have reduced the thickness of asphalt layer by approximately 10%. Additionally, polyvinyl alcohol fiber has increased the performance of the asphalt mixtures concerning of resilient modulus and dynamic creep. Furthermore, the correlation between CSS and SCSM was strong, which indicates that evaluation of permanent deformation using CSS and SCSM parameters provides better actual assessment than accumulation strain.

Self-humidifying membrane electrode assembly with dual cathode catalyst layer structure prepared by introducing polyvinyl alcohol into the inner layer

Short-term constant voltage discharge test of the self-humidifying MEAs with different cathode structure at 60 °C and 30 psi under 20% RH.

PVA assisted low temperature anatase to rutile phase transformation (ART) and properties of titania nanoparticles

Anatase to rutile phase transformation (ART) of titania nanoparticles is observed at very low temperature (180 °C) just by introducing polyvinyl alcohol (PVA) during co-precipitation followed by hydrothermal synthesis. The detailed investigations pertaining to the structural, optical and electrochemical properties of the nanosized titania and titania/PVA nanohybrid has been carried out. The crystallite size and crystal structure is confirmed using X-ray diffraction (XRD). Transmission electron microscopic (TEM) image reveals formation of spherical NPs in both the cases. Identification of functional groups is done using Fourier transform infrared spectroscopy (FTIR). The photoluminescence studies showed that emission slightly shifts towards higher wavelength side with remarkable decrease in intensity for TiO2/PVA nanocomposite (rutile samples). The remarkable decrease in PL intensity in TiO2/PVA nanocomposite (rutile samples) is explained considering the surface passivation during growth process. Ion transportation is monitored via Cyclic voltammetric (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. A significant enhancement of peak cathodic current in case of nanocomposite modified electrode is observed. It is assumed that TiO2/PVA (rutile) nanoparticles provided the conducting path for the electrons and hence enhanced the electrochemical reaction.

A novel and simple microcontact printing technique for tacky, soft substrates and/or complex surfaces in soft tissue engineering

Microcontact printing (μCP) has attracted much interest due to its simplicity and wide range of applications. However, when conventional μCP is applied to soft and/or tacky substrates, substrate sagging and difficulty in stamp removal cause non-conformance in the patterns. Moreover, it is almost impossible to apply conventional μCP on complex or wavy surfaces. In this study, we developed a novel yet simple trans-print method to create efficient micropatterning on soft and/or tacky substrates such as polydimethylsiloxane and polyacrylamide gel, and also on curved surfaces, by introducing polyvinyl alcohol film as a trans-print media. This technique is simple as it only involves one trans-print step and is also cost-effective. Most importantly, this technique is also versatile and we have proven this by printing various designs on more complex non-flat surfaces using various proteins as inks. The quality of the trans-printed pattern was excellent with high reproducibility and resolution as verified by immunostaining. Human mesenchymal stem cells cultured on these patterns displayed good conformance on the soft and tacky substrates printed using this technique. These results suggest that this novel trans-print technique can be extended to a potentially generic methodology for μCP of other proteins and biomolecules, other shapes and sizes, and cells, and will also be useful in three-dimensional micropatterning for soft tissue engineering.

Impact of structural variations in hollow yarn on heat and moisture transport properties of fabrics

The use of hollow/microporous yarns plays an important role in enhancing the thermo‐physiological comfort properties of fabrics. Depending on structural variations in hollow yarn, heat and moisture regulation behaviours of fabrics can be affected significantly. In this study, three types of hollow cotton yarn fabrics, produced by introducing polyvinyl alcohol (PVA) filament in the core, PVA staple fibres in the blend and PVA filament in doubling with cotton spun yarn, are studied. All three types of pre‐hollow yarns and reference yarns are made with a variation in spinning technique (single roving/double roving) to prepare eight single jersey knitted fabrics. The hollow/microporous structure of the yarn is created by dissolving the PVA fibres using hot washing of the fabrics. On overall evaluation of the fabric’s thermo‐physiological comfort properties, the doubled hollow yarn fabrics are found to be better than other fabrics. In general, thermal resistance, thermal absorptivity, wicking and drying properties of all types of hollow yarn fabrics increase after repeated laundering, while air permeability, water vapour permeability and water absorbency of hollow yarn fabrics mostly decrease. In contrast with fabrics made from yarn produced through single roving technique, use of double roving technique only improves fabric water vapour permeability.