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Hemicellulose, one of the most abundant biopolymers next to cellulose, has been considered as a potential substitute to synthetic polymers. Film casting from water is the most basic route for material applications of xylan. However, depending on plant sources and separation methods, xylans do not always form films and the related mechanism is unclear, which significantly hinders their material applications. We extensively characterized various fractions of bagasse xylan to understand the molecular features promoting the film formation.The side groups of xylans or impurities contributed to the prevention of excessive aggregation or crystallization of xylan molecules, leading to the film-forming capacity. However, once the film is formed, the side groups do not seem to be necessarily contributing to the mechanical resistance.

As one of the most abundant natural polymers in nature, polysaccharides have the potential to replace petroleum-based polymers that are difficult to degrade in paper coatings. Polysaccharide molecules have a large number of hydroxyl groups that can bind strongly with paper fibers through hydrogen bonds. Chemical modification can also effectively improve the mechanical, barrier, and hydrophobic properties of polysaccharide-based coating layers and thus can further improve the related properties of coated paper. Polysaccharides can also give paper additional functional properties by dispersing and adhering functional fillers, e.g., conductive particles, catalytic particles or antimicrobial chemicals, onto paper surface. Based on these, this paper reviews the application of natural polysaccharides, such as cellulose, hemicellulose, starch, chitosan, and sodium alginate, and their derivatives in paper coatings. This paper analyzes the improvements and influences of chemical structures and properties of polysaccharides on the mechanical, barrier, and hydrophobic properties of coated paper. This paper also summarizes the researches where polysaccharides are used as the adhesives to adhere inorganic or functional fillers onto paper surface to endow paper with great surface properties or special functions such as conductivity, catalytic, antibiotic, and fluorescence.

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