Electrospinner: Review of functional cellulose-based materials: hydrophobic, high-strength, degradable, green and environmentally friendly with wide applications!

Background

Due to the rapid population growth and high energy demand, the increasing use of fossil energy has exacerbated various environmental and climate problems. Among these problems, "white pollution" from discarded plastics poses a major threat to the sustainable development of human society. Therefore, the development of biodegradable green biopolymers is of great significance.

Recently, the team of Professor Lai Yuekun of Fuzhou University published a review article entitled "Recent Advances in Functional Cellulose-Based Materials: Classification, Properties, and Applications" in Advanced Fiber Materials, systematically summarizing the latest research progress based on cellulose films, and reviewing them from the aspects of classification, performance and application. According to the various forms of cellulose (such as nanocrystals, nanospheres and hollow ring cellulose) and cellulose derivatives (such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and cellulose acetate), the mechanical properties, antibacterial properties, air permeability and hydrophobicity of the modified cellulose films are summarized, and the performance improvement mechanism is discussed and analyzed. In addition, the typical applications of cellulose composites, such as food packaging, medical supplies and electronic devices, are outlined; and the challenges faced by the development of cellulose-based materials and future development trends are prospected.

The main point of this paper

First, the development process of cellulose derivatives is introduced. Since the linear chain structural unit of cellulose contains three reactive hydroxyl groups, it is conducive to esterification or etherification reaction with chemical reagents, and is mainly divided into three categories: cellulose ether, cellulose ester and cellulose ether ester. In addition to the chemical diversity provided by the -OH group, the unique molecular structure of cellulose also gives it chirality, hydrophilicity and degradability. As shown in Figure 1 (a-c), the cellulose nanocrystal @ methyl cellulose (CNC@MC) membrane-based smart bandage prepared by dissociation, hydrolysis, dialysis and other processes from recycled waste paper has good flexibility and transparency; as shown in Figure 1 (d-g), the bacterial cellulose-CMC composite membrane is prepared by in situ fermentation technology for the conversion of osmotic energy. CMC is tightly attached to the surface of bacterial cellulose, which is conducive to the construction of micro-nano channels of different sizes, and with the increase of CMC content, the pore size gradually increases.

Secondly, the inherent hydrophilicity of cellulose seriously affects its application in "paper-based plastic substitutes". As shown in Figure 2 (a-c), a hydrophilic/superhydrophobic patterned surface was developed by self-assembling CNC/wax microspheres, which enhanced the droplet capture and transportation performance. In the superhydrophobic state, due to the presence of an air layer, the droplets can roll off the membrane surface. When the water droplets contact the surface, they gradually deform. The binding force of the membrane surface is 27.6 µN, and the difference in rolling angle/hysteresis angle increases with the increase of CNC content. As can be seen from Figure 2 (d-f), due to the strong binding force between the interface and the droplets, the contact angle and rolling angle of the droplets before and after the impact of gravel do not change significantly, showing excellent performance stability. Figure 2 (g-h) shows a fluorine-free, high-efficiency, biodegradable waterproof and breathable film prepared by heat treatment and impregnation of hyperbranched polymer cellulose acetate (CA). The interconnected network and high porosity provide sufficient channels for water transport, making the film permeable. As can be seen from Figure 2 (i-k), the droplet containing the dye rolls off the surface of the sample. After multiple sandpaper rubbing and long-term ultrasonic washing, the contact angle of the sample is almost unchanged. The development of fluorine-free, hydrophobic, and biodegradable cellulose-based membranes reduces the impact on the natural environment. At the same time, its high-efficiency hydrophobic performance in complex environments meets the conventional use requirements.

Finally, the application of cellulose in disposable straws, tableware, and cling film is discussed. Figure 3 (a-b) shows a composite straw based on all-natural micro-nano cellulose. Cellulose micro-nano fibers are obtained from sugarcane bagasse and wood. The straw is prepared through drying and other processes. The edge of the membrane is sealed by hydrogen bonds and degraded in the natural environment for 120 days, which is almost unchanged like plastic straws. The flexural and tensile strengths of the straws reach 6.9 and 70 MPa, respectively. Figure 3 (c-e) shows that in the cellulose hybrid chain, cellulose nanofibers are arranged hexagonally around cellulose microfibers, and the adjacent cellulose fibers slide relative to each other under stress. As can be seen from Figure 3 (f-i), disposable biodegradable tableware made of Sargassum cellulose nanofibers (SCNF) has excellent mechanical and thermal properties. After Ca2+ is introduced into the SCNF suspension, the coordination bonds and abundant hydrogen bonds between the celluloses make the suspension form a hydrogel. After heating and pressurizing to remove most of the free water, the SCNF-based membrane material is prepared, and various tableware such as knives and forks can be prepared by molding; in addition, the introduction of specific metal ions can improve the antibacterial properties and water droplet wettability of the SCNF membrane, and by regulating the disorder and nanopores of the fibers, its mechanical properties are improved, and it can withstand different gravity.

In summary, cellulose-based membranes have made great progress in various fields, and there are still scientific and technological problems to be solved in practical applications: how to commercialize large-scale production, further improve water resistance and stability, and develop multifunctional cellulose-based materials and functional integration.

Electrospinning Nanofibers Article Source:

https://link.springer.com/article/10.1007/s42765-024-00454-0