A tough, stretchable, adhesive and electroconductive polyacrylamide hydrogel sensor incorporated with sulfonated nanocellulose and carbon nanotubes.

Recently, hydrogel sensors have been widely applied in wearable and portable electronics, but the low mechanical property, intolerance of fatigue, and low sensitivity and adhesion limit their further applications. In this study, sulfonated nanocellulose (SCNF) with dual functionality was blended into polyacrylamide (PAM) hydrogel matrix to reinforce the mechanical strength and facilitate the homogeneous dispersion of carbon nanotubes (CNTs). The SCNF-CNT/PAM hydrogel was designed through free radical polymerization to achieve commendable mechanical, electrical, and multifunctional properties. The environmental-friendly SCNF serves as bio-templates to facilitate the assembling of CNT into integrated SCNF-CNT structures with good dispersity, thus enabling the establishment of an integrated conducting and reinforcing network. The fabricated SCNF-CNT/PAM hydrogel exhibited outstanding compressive strength (∼0.45 MPa at 50 % strain), tensile strength (∼169.12 kPa), and antifatigue capacity under cyclic stretching and pressing. Furthermore, the multifunctional sensors assembled using this hydrogel demonstrated high strain sensitivity (gauge factor ~ 3.7 at 100-400 % strain) and effectively detected human motions. This design principle provides promising prospects for constructing next-generation multifunctional flexible sensors, and the integration of these distinctive properties enables the prepared composite hydrogels to find potential applications in various areas, such as implantable soft electronic devices, electronic skin, and human movement monitoring.

Tailoring Functionality of Nanocellulose: Current Status and Critical Challenges.

Nanocellulose (NC) isolated from natural cellulose resources, which mainly includes cellulose nanofibril (CNF) and cellulose nanocrystal (CNC), has garnered increased attention in recent decades due to its outstanding physical and chemical properties. Various chemical modifications have been developed with the aim of surface-modifying NC for highly sophisticated applications. This review comprehensively summarizes the chemical modifications applied to NC so far in order to introduce new functionalities to the material, such as silanization, esterification, oxidation, etherification, grafting, coating, and others. The new functionalities obtained through such surface-modification methods include hydrophobicity, conductivity, antibacterial properties, and absorbability. In addition, the incorporation of NC in some functional materials, such as films, wearable sensors, cellulose nanospheres, aerogel, hydrogels, and nanocomposites, is discussed in relation to the tailoring of the functionality of NC. It should be pointed out that some issues need to be addressed during the preparation of NC and NC-based materials, such as the low reactivity of these raw materials, the difficulties involved in their scale-up, and their high energy and water consumption. Over the past decades, some methods have been developed, such as the use of pretreatment methods, the adaptation of low-cost starting raw materials, and the use of environmentally friendly chemicals, which support the practical application of NC and NC-based materials. Overall, it is believed that as a green, sustainable, and renewable nanomaterial, NC is will be suitable for large-scale applications in the future.

A comprehensive review of chitosan applications in paper science and technologies.

Using environmentally friendly biomaterials in different aspects of human life has been considered extensively. In this respect, different biomaterials have been identified and different applications have been found for them. Currently, chitosan, the well-known derivative of the second most abundant polysaccharide in the nature (i.e., chitin), has been receiving a lot of attention. This unique biomaterial can be defined as a renewable, high cationic charge density, antibacterial, biodegradable, biocompatible, non-toxic biomaterial with high compatibility with cellulose structure, where it can be used in different applications. This review takes a deep and comprehensive look at chitosan and its derivative applications in different aspects of papermaking.

Lignocellulosic hydrogel from recycled old corrugated container resources using ionic liquid as a green solvent.

Lignocellulosic hydrogels are valuable bio-products that have been considered widely in recent investigations. Also, application of low value recycled fibers for high value added products can be of much interest. In this respect, current research has focused on producing hydrogel from recycled old corrugated container (OCC) resources, using 1-butyl-3-methyl-imidazolium chloride ionic liquid (IL) as a green solvent. The results indicated that the IL successfully dissolved OCC fibers, allowing the production of lignocellulosic hydrogel. Considering total water absorption amount as a main criterion for evaluation of hydrogels, the fabricated hydrogel showed promising results (up to 4700% water absorption). X-ray diffraction analysis confirmed obvious reduction in cellulose material crystallinity and crystallite size as a result of the process. Field emission scanning electron microscopy also demonstrated the microstructure of the hydrogel, pore size and shape in the hydrogel, which well supported the laboratory research results. Furthermore, the effect of processing parameters showed that specimens washed with distilled water as the anti-solvent resulted in the highest water absorption. Infrared spectroscopy can be used to suggest the presence of more lignin content in the hydrogel washed with ethanol. Moreover, the best water re-absorption results were observed for the hydrogel washed with distilled water.

The performance of chitosan with bentonite microparticles as wet-end additive system for paper reinforcement.

In this research, the effect of bentonite micro-particles on the performance of chitosan as a new additive system for improving the dry strengths of acidic papermaking was studied. Chitosan, an abundant carbohydrate biopolymer, in 4 dosages (0, 0.75, 1.25 and 2% based on dry weight of pulp) was applied with bentonite in 4 dosages (0, 0.3, 0.6 and 0.9% based on oven-dry weight of pulp). Although the addition of chitosan up to 0.75% (without bentonite) improved tensile index and burst index, but the addition of more chitosan decreased all mechanical properties in comparison with the control sample. The application of bentonite in combination with chitosan had a significant impact on chitosan performance in mechanical properties. The best results were obtained with 0.3% bentonite consumption. Visual formation ranking had a proper correlation with this obtained results. The micro-kjeldahl indirectly confirmed chitosan retention in the treated paper with chitosan/bentonite.