Hydrophobic enzymatic cellulose nanocrystals via a novel, one-pot green method

• Published in: Carbohydrate research 2023-12, Vol.534, p.108970-108970, Article 108970
• Main Authors: de Carvalho Benini, Kelly Cristina Coelho, de Souza Marotti, Braz, Arantes, Valdeir
• Format: Article
• Language: English
• Subjects: Cellulose nanocrystals; Esterification; Fatty acid; Green; Hydrophobic nanocellulose; Hydrophobization
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2023.108970

Cellulose nanocrystals (CNCs) are a rapidly growing bionanomaterial with remarkable properties that have been harnessed in various applications, including mechanical reinforcement, biomedical materials, and coatings. However, for non-water-based applications, hydrophobization of CNCs while preserving their integrity is crucial. In this study, we propose a new eco-friendly, one-pot surface esterification method for hydrophobizing enzymatic CNCs in aqueous suspension without solvent exchange. By establishing an appropriate set of reaction conditions, it was possible to create a miscibility gradient that enabled a low-cost, and renewable fatty acid to be utilized as an acyl donor and solvent, allowing direct hydrophobic modification of the as-produced aqueous suspension of enzymatic CNC. FT-IR and AFM-IR analyses confirmed the formation of ester groups, while 13C NMR confirmed the emergence of carboxyl groups. XPS revealed a high degree of surface substitution (0.39) in the modified CNC, while a substantial increase in contact angle (from 40 to approximately 90o) quantitatively confirmed the high efficiency of the enzymatic CNC's hydrophobic modification. Additionally, important properties such as morphology remained practically unchanged, except for a slight increase in thermal stability and crystallinity of the CNCs. Therefore, hydrophobic enzymatic CNCs were successfully produced via a simple, scalable, and environmentally friendly approach without compromising their properties. These hydrophobic CNCs have the potential to enhance nanocomposite compatibility, improve packaging performance for electronics and foods, optimize adhesion in coatings, and offer advancements in cosmetics and drug delivery. However, comprehensive studies are needed to confirm their applicability across these sectors. [Display omitted] •New one-pot method achieves hydrophobic enzymatic CNCs in aqueous suspension.•FT-IR, AFM-IR, and 13C NMR confirm successful esterification and carboxyl group appearance.•Modified CNCs show an increased contact angle, approximately 90°.•Hydrophobic CNCs maintain morphology with improved thermal stability and crystallinity.•Hydrophobic CNCs offer potential in packaging, coatings, cosmetics, and drug delivery systems.