Green Approaches to the Surface Modification of Cellulose

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Nanocellulose, with its natural abundance and unique properties, has emerged as a promising building block for sustainable materials. However, its full potential can only be unlocked through chemical modifications that tailor its surface characteristics to meet the demands of modern applications. This review has highlighted a range of organic reactions, such as esterification, click chemistry, silylation, and urethanization, that have been effectively used to modify nanocellulose in environmentally friendly ways. These modifications have improved its compatibility with polymers, increased its thermal stability, introduced reactive sites, and expanded its functionality in areas like packaging, biomedicine, and electronics. What stands out is how green chemistry approaches are steadily replacing traditional, harsher methods. The use of ionic liquids, deep eutectic solvents, and even enzymes has made it possible to achieve high levels of modification while minimizing environmental impact. Click reactions, for example, offer a highly selective and efficient way to attach functional molecules under mild conditions, opening doors to innovative material design. Looking forward, there is still room for growth. Developing safer alternatives to isocyanates, improving the uniformity of surface modifications, and scaling up eco-friendly methods for industrial use are some of the challenges that researchers need to tackle. There is also a growing interest in creating smart cellulose-based materials, those that can respond to changes in temperature, light, or pH, or even self-heal. In addition to chemical efficiency, the environmental and economic viability of cellulose modification strategies is increasingly important for large-scale adoption. Green transformation routes that rely on renewable feedstocks, recyclable solvents, and mild reaction conditions offer clear advantages in reducing carbon footprints and process energy demand. For example, water-based systems, ionic liquids with high recyclability, and deep eutectic solvents minimize volatile organic solvent use while enabling efficient cellulose functionalization. From an economic perspective, the availability of cellulose from regional biomass sources, combined with scalable surface modification techniques, supports cost-effective production. However, challenges remain in balancing solvent cost, recovery efficiency, and reaction scalability, particularly for homogeneous modification routes. Future work should also focus on how these modified materials behave over their entire life cycle, from production to disposal. Understanding their environmental footprint will be key to ensuring that the shift toward biobased materials truly supports sustainability goals. Looking ahead, the field of nanocellulose modification offers exciting opportunities to create truly sustainable, high-performance materials. A major goal is to move away from toxic reagents like isocyanates and adopt safer, eco-friendly alternatives such as cyclic carbonates that can achieve similar chemical linkages without health or environmental risks. Enzyme-based approaches also hold great promise; they can carry out precise modifications under mild conditions, using little energy and producing minimal waste. Future developments in cellulose modification are expected to increasingly incorporate enzyme-based and biocatalytic strategies, which offer high regioselectivity and low environmental impact, working alongside the organic reaction routes discussed in this review. Another exciting direction is the use of advanced “click” chemistries that allow researchers to attach multiple functional groups in a controlled, stepwise manner. This opens the door to designing smart materials that respond to temperature, pH, or light, or that have properties like antimicrobial activity or self-healing behavior. As these materials find new uses in flexible electronics, wearable sensors, medical devices, and even responsive packaging, there will be a growing need to control how and where the modifications happen on the nanocellulose surface. At the same time, it is important to think about the full life cycle of these products, how they are made, used, and eventually disposed of. Integrating green chemistry with life-cycle thinking and cost analysis will be crucial to ensure that the materials we develop are not only functional but also practical and truly sustainable. With continued innovation, green surface modification of nanocellulose holds great promise for creating the next generation of materials, ones that are not only high-performing but also kind to the planet.

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