“…6. The lower concentrations of PVA yielded more opaque hydrogels whilst PVA20 hydrogels were translucent, such an observation has also been reported in a previous study [22]. This variation in opacity arises due to the difference in solution viscosity, since lower concentrations of the polymer solution imposes less restriction on the movement of the PVA chains thereby making it easier for them to crystallise more effectively.…”
Section: Resultssupporting
confidence: 79%
“…This results in a hydrogel with large crystallites that scatter more visible light, which makes the hydrogels appear opaque. An increase in PVA concentration results in an aqueous solution with high viscosity and more PVA chains to form crystallites, however the crystallite size decreases as there is restricted growth and therefore scatters less visible light, which results in translucent hydrogels [22]. Fig.…”
Inspired by the double network hydrogel systems we report the formulation of dual networks, which expands the repertoire of this class of materials for potential biomedical applications. The tough dual network hydrogels were designed through sequential interpenetrating polymer formation, applying green chemistry and low-cost methods, devoid of any initiator-activator complexes that may pose risks in biomedical applications. The dual networks were synthesized in two steps, firstly the water soluble poly(vinyl alcohol) was subjected to cryogelation that formed the first network, which was then expanded by intrusion of a dilute solution of sodium alginate and complexed with a solution of calcium chloride under ambient conditions and further freeze-thawed. These hydrogels are flexible, ductile and porous with the ability to absorb and retain fluids as well as possess the versatility to easily incorporate biological molecules/drugs/antibiotics to be applied in tissue matrices or drug delivery systems. The dual network hydrogels can be tailored to have varying mechanical properties, shapes, size, thickness and particularly can be made physically porous if required, to suit the users intended application.
“…6. The lower concentrations of PVA yielded more opaque hydrogels whilst PVA20 hydrogels were translucent, such an observation has also been reported in a previous study [22]. This variation in opacity arises due to the difference in solution viscosity, since lower concentrations of the polymer solution imposes less restriction on the movement of the PVA chains thereby making it easier for them to crystallise more effectively.…”
Section: Resultssupporting
confidence: 79%
“…This results in a hydrogel with large crystallites that scatter more visible light, which makes the hydrogels appear opaque. An increase in PVA concentration results in an aqueous solution with high viscosity and more PVA chains to form crystallites, however the crystallite size decreases as there is restricted growth and therefore scatters less visible light, which results in translucent hydrogels [22]. Fig.…”
Inspired by the double network hydrogel systems we report the formulation of dual networks, which expands the repertoire of this class of materials for potential biomedical applications. The tough dual network hydrogels were designed through sequential interpenetrating polymer formation, applying green chemistry and low-cost methods, devoid of any initiator-activator complexes that may pose risks in biomedical applications. The dual networks were synthesized in two steps, firstly the water soluble poly(vinyl alcohol) was subjected to cryogelation that formed the first network, which was then expanded by intrusion of a dilute solution of sodium alginate and complexed with a solution of calcium chloride under ambient conditions and further freeze-thawed. These hydrogels are flexible, ductile and porous with the ability to absorb and retain fluids as well as possess the versatility to easily incorporate biological molecules/drugs/antibiotics to be applied in tissue matrices or drug delivery systems. The dual network hydrogels can be tailored to have varying mechanical properties, shapes, size, thickness and particularly can be made physically porous if required, to suit the users intended application.
“…8 The crystallization of PVA conducted at low temperatures (−15°C to −10°C) via freezing–thawing method resulted in physical cross-linking and the formation of self-repairing hydrogels was achieved. 9,10 PVA-based self-healable hydrogels were also produced by using nanoparticles such as iron oxide and silver. 11…”
Polyvinyl alcohol (PVA)/cotton (Co) woven fabrics were produced by constructing Co as warp yarns and PVA as weft yarns in the fabric structure. As-prepared PVA/Co fabrics were treated with borax/water solution. Because of the simultaneous dissolution and gelation of PVA yarn in the fabric and transformation of PVA molecules into cross-linked gel structures, gel penetrated among the yarns in the matrix form and hence Co yarn-reinforced composite hydrogels were obtained. The retention time of water by composite hydrogels was first increased and then decreased by increasing borax concentration in the cross-linker solution. With yarn reinforcing, the tensile strength of hydrogel structure significantly increased. Mechanical properties of hydrogel composites were very variable depending on water content in the structure and tensile strength tremendously increased when water evaporated from the structure. Thermal and chemical characterizations of yarn-reinforced hydrogel composites were conducted in addition to swelling and mechanical analysis to investigate the performance of the hydrogel composites.
“…In order to expand the application of PVA, much attention has been paid to fabricating functional PVA composites. The existence of hydrogen-bonding groups in PVA structure and the ability to form hydrogen bonds makes PVA suitable for mixing with other materials to improve its functional properties [14,15]. In previous studies, the prepared silica in situ enhanced PVA/chitosan biodegradation films [16], PVA/tea polyphenol composite films [17], PVA reinforced with cellulose nanocrystals or cellulose nanofibers (CNF) [18], and CNF/PVA-borax hybrid foams [19] had better functional properties than PVA itself, from the perspective of packaging-industry application.In recent years, carbon materials have been paid much attention for the preparation of functional composites.…”
In this study, the low-cost processing residue of Radiata pine (Pinus radiata D. Don) was used as the lone carbon source for synthesis of CQDs (Carbon quantum dots) with a QY (The quantum yield of the CQDs) of 1.60%. The CQDs were obtained by the hydrothermal method, and +a PVA-based biofilm was prepared by the fluidized drying method. The effects of CQDs and CNF (cellulose nanofibers) content on the morphology, optical, mechanical, water-resistance, and wettability properties of the PVA/CQDs and PVA/CNF/CQDs films are discussed. The results revealed that, when the excitation wavelength was increased from 340 to 390 nm, the emission peak became slightly red-shifted, which was induced by the condensation between CQDs and PVA. The PVA composite films showed an increase in fluorescence intensity with the addition of the CNF and CQDs to polymers. The chemical structure of prepared films was determined by the FTIR spectroscopy, and no new chemical bonds were formed. In addition, the UV transmittance was inversely proportional to the change of CQDs content, which indicated that CQDs improved the UV barrier properties of the films. Furthermore, embedding CQDs Nano-materials and CNF into the PVA matrix improved the mechanical behavior of the Nano-composite. Tensile modulus and strength at break increased significantly with increasing the concentration of CQDs Nano-materials inside the Nano-composite, which was due to the increased in the density of crosslinking behavior. With the increase of CQDs content (>1 mL), the water absorption and surface contact angle of the prepared films decreased gradually, and the water-resistance and surface wettability of the films were improved. Therefore, PVA/CNF/CQDs bio-nanocomposite films could be used to prepare anti-counterfeiting, high-transparency, and ultraviolet-resistant composites, which have potential applications in ecological packaging materials.
IntroductionPolyvinyl alcohol (PVA) is a kind of semi-crystalline polymer with a linear structure and strong hydrogen bonds intermolecular. It has been widely used in papermaking [1], textiles [2], coatings [3], adhesives [4], packaging [5], and biomedicine [6] because of its toughness [7], adhesiveness [8], biocompatibility [9], swelling behavior [10], lack of toxicity [11], and sufficient thermal stability; it is also odorless and tasteless. However, PVA is highly hydrophilic and water-soluble [12], and its light transmittance is not suitable for light-barrier packaging [13]. In order to expand the application of PVA, much attention has been paid to fabricating functional PVA composites. The existence of hydrogen-bonding groups in PVA structure and the ability to form hydrogen bonds makes PVA suitable for mixing with other materials to improve its functional properties [14,15]. In previous studies, the prepared silica in situ enhanced PVA/chitosan biodegradation films [16], PVA/tea polyphenol composite films [17], PVA reinforced with cellulose nanocrystals or cellulose nanofibers (CNF) [18], and CNF/PVA-borax hybrid foams [19] had...
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