Polyvinyl alcohol/chitosan based nanocomposite organohydrogel flexible wearable strain sensors for sports monitoring and underwater communication rescue.

Hydrogel-based flexible wearable sensors have garnered significant attention in recent years. However, the use of hydrogel, a biomaterial known for its high toughness, environmental friendliness, and frost resistance, poses a considerable challenge. In this study, we propose a stepwise construction and multiple non-covalent interaction matching strategy to successfully prepare dynamically physically crosslinked multifunctional conductive hydrogels. These hydrogels self-assembled to form a rigid crosslinked network through intermolecular hydrogen bonding and metal ion coordination chelation. Furthermore, the freeze-thawing process promoted the formation of poly(vinyl alcohol) microcrystalline domains within the amorphous hydrogel network system, resulting in exceptional mechanical properties, including a tensile strength (2.09 ± 0.01 MPa) and elongation at break of 562 ± 12 %. It can lift 10,000 times its own weight. Additionally, these hydrogels exhibit excellent resistance to swelling and maintain good toughness even at temperatures as low as -60 °C. As a wearable strain sensor with remarkable sensing ability (GF = 1.46), it can be effectively utilized in water and underwater environments. Moreover, it demonstrates excellent antimicrobial properties against Escherichia coli (Gram-negative bacteria). Leveraging its impressive sensing ability, we combine signal recognition with a deep learning model by incorporating Morse code for encryption and decryption, enabling information transmission.

High-Strength, Freeze-Resistant, Recyclable, and Biodegradable Polyvinyl Alcohol/Glycol/Wheat Protein Complex Organohydrogel for Wearable Sensing Devices.

The application of flexible wearable sensing devices based on conductive hydrogels in human motion signal monitoring has been widely studied. However, conventional conductive hydrogels contain a large amount of water, resulting in poor mechanical properties and limiting their application in harsh environments. Here, a simple one-pot method for preparing conductive hydrogels is proposed, that is, polyvinyl alcohol (PVA), wheat protein (WP), and lithium chloride (LiCl) are dissolved in an ethylene glycol (EG)/water binary solvent. The obtained PVA/EG/WP (PEW) conductive organohydrogel has good mechanical properties, and its tensile strength and elongation at break reach 1.19 MPa and 531%, respectively, which can withstand a load of more than 6000 times its own weight without breaking. The binary solvent system composed of EG/water endows the hydrogel with good frost resistance and water retention. PEW organohydrogel as a wearable strain sensor also has good strain sensitivity (GF = 2.36), which can be used to detect the movement and physiological activity signals in different parts of the human body. In addition, PEW organohydrogels exhibit good degradability, reducing the environmental footprint of the flexible sensors after disposal. This research provides a new and viable way to prepare a new generation of environmentally friendly sensors.

Preparation and Properties of Novel Crosslinked Polyphosphazene-Aromatic Ethers Organic-Inorganic Hybrid Microspheres.

A series of novel crosslinked polyphosphazene-aromatic ether organic-inorganic hybrid microspheres with different structures were prepared via precipitation polycondensation between hexachlorocyclotriphosphazene (HCCP) and bisphenol monomers. The bisphenol monomers have different numbers of -CF3 in the side group, which correspond to distinct oligomeric species-absorbing mechanisms. The wetting behavior of the microsphere surface was evaluated using a water contact angle (CA) measurement, which increased with the increase in the content of -CF3 in polyphosphazene. We also investigated the effects of HCCP concentration and ultrasonic power on the morphology of the microspheres.

Preparation of a PVA/Chitosan/Glass Fiber Composite Membrane and the Performance in CO2 Separation.

In this study, a novel composite membrane was developed by casting the mixed aqueous solution of chitosan (CS) and polyvinyl alcohol (PVA) on a glass fiber microporous membrane. The polymeric coating of a composite membrane containing amino groups and hydroxyl groups has a favorable CO2 affinity and provides an enhanced CO2 transport mechanism, thereby improving the permeance and selectivity of CO2. A series of tests for the composite membranes were taken to characterize the chemical structure, morphology, strength, and gas separation properties. ATR-FTIR spectra showed that the chemical structure and functional group of the polymer coating had no obvious change after the heat treatment under 180 °C, while SEM results showed that the composite membranes had a dense surface. The gas permeance and selectivity of the composite membrane were tested using single gases. The results showed that the addition of chitosan can increase the CO2 permeance which could reach 233 GPU. After a wetting treatment, the CO2 permeance (454 GPU) and gas selectivity (17.71) were higher than that of dry membranes because moisture promotes the composite membrane transmission. After a heat treatment, the permeance of N2 decreased more significantly than that of CO2, which led to an increase in CO2/N2 selectivity (10.0).