Cellulose, the most abundant biopolymer on Earth, plays a crucial role in shaping the structural integrity of plant cell walls and is found in diverse living organisms. Its unique properties and versatile nature make it a key player in the development of sustainable materials.
Cellulose is a linear syndiotactic homopolymer composed of d-anhydroglucopyranose units linked by β-(1→4)-glycosidic bonds. The repeating unit, cellobiose, forms strong microfibrils through aggregation, resulting in crystalline regions that are linked by amorphous segments allowing a little flexibility to the microfibrils. The extensive hydrogen bonding between cellulose chains contributes to its high strength, stiffness, durability, and biocompatibility.
Chemical modification of cellulose yields derivatives with altered properties, expanding its applications. The abundant hydroxyl groups allow for etherification, carboxymethylation, cyanoethylation, and hydroxypropylation, producing cellulose derivatives like ester-cellulose acetate and ether-methylcellulose/carboxymethyl cellulose. These derivatives offer diverse properties compared to native cellulose, enhancing their utility. Chemical treatment of cellulose can deconstruct it into its monomer glucose. These monomers, such as lactic acid, levulinic acid, sorbitol, and 5-hydroxymethylfurfural, serve as valuable bio-based polymer platforms, contributing to the development of sustainable materials like PLA or PEF.
Nanoscale cellulose fibers, including cellulose nanocrystals (CNCs), cellulose nanofibers (CNFs), and bacterial cellulose (BC), offer unique properties. CNCs and CNFs, obtained through top-down approaches, exhibit high Young’s moduli, high specific surface areas, increased crystallinities, and improved thermal stabilities. BC, produced through bacterial processes, boasts higher purity, crystallinity, and exceptional mechanical strength.
The versatility of cellulose nanoparticles opens up a wide range of applications. Their low density, biodegradability, high aspect ratio, strength, stiffness, reinforcing properties, and transparency make them ideal for use in various industries, including biomaterials and bio-based polymers.
As we navigate towards a more sustainable future, cellulose emerges as a key player in the development of eco-friendly materials. Its abundance, unique structure, and adaptability through chemical modification make it a cornerstone in the creation of biomaterials and bio-based polymers. From cellulose derivatives to nanoscale fibers, the applications are vast, and the potential for innovation and positive environmental impact is immense.