1. Introduction

Nanocellulose ( NC ) is a green nanomaterial derived from natural cellulose, with high specific surface area, high crystallinity, excellent mechanical properties and renewability. However, natural nanocellulose surfaces are rich in hydroxyl groups and exhibit strong hydrophilicity, which limits its application in non-polar polymers, oily systems and hydrophobic substrates. To this end, scientific researchers and enterprises have transformed their surface into hydrophobic nanocellulose through chemical modification or physical treatment, greatly expanding their application space.

Keywords: nanocellulose, hydrophobic modification, esterification, silanization, oil-water separation, composite materials

2. Preparation process of hydrophobic nanocellulose

Modification method	Typical reactants /means	advantage	shortcoming
Esterification reaction	Fatty acid anhydride, stearic anhydride, isocyanate	Mature process and significant hydrophobicity	Partial reaction requires organic solvents
Silenization modification	Triethoxyoctylsilane, methyltrichlorosilane	Hydrophobic and long-lasting, suitable for composite materials	Higher cost
Etherification reaction	Alkyl bromide, alkyl chloride	Good stability	Reaction conditions are harsh
Graft polymerization	Polyacrylate, PMMA grafting	Good compatibility with polymers	Complex process
Surfactant adsorption	Cationic /nonionic surfactants	Simple operation, low cost	Hydrophobicity is prone to loss
Plasma /self-assembly	Fluorine /Silicon-containing thin film deposition	Strong hydrophobicity and high durability	High equipment cost

Summary : Chemical modification methods are suitable for industrial scale, and physical methods are suitable for rapid application and experimental research.

3. ^{Performance characteristics of} hydrophobic nanocellulose

Hydrophobicity is significantly improved : the water contact angle is increased from <40° to >120°。

Enhanced dispersion : Dispersing evenly in hydrophobic substrates such as polypropylene and polylactic acid.

Improved mechanical properties : It significantly improves the strength of composite materials as a reinforcement.

Improved water resistance : reduces hygroscopicity and maintains structural stability.

4. Application prospects

Polymer composite materials

It is used in plastic reinforcement such as PE 、PP 、PLA to enhance mechanical strength and heat resistance.

Used for rubber reinforcement to improve wear resistance and elasticity.

Functional film and coating

Waterproof coatings, food packaging films, oil-resistant and moisture-resistant materials.

A barrier reinforcement material for biodegradable plastics.

Oil-water separation and environmental governance

Prepare superhydrophobic / super oleophilic materials for industrial wastewater treatment and offshore oil spill recovery.

Energy and Electronics

The battery separator has both lightweight and liquid immersion resistance.

Used as an electrically insulating material and functional coating.

Biomedicine

Hydrophobic drug controlled release carrier.

Improve the stability of materials in physiological environment in tissue engineering.

5. Market prospects and industrialization trends

Application areas	Market size growth point (forecast to 2030)	Technical breakthrough points
Packaging materials	>10% CAGR	Environmentally friendly and biodegradable needs
Polymer composite materials	Car lightweight and 3D printing requirements	Cellulose -polymer compatibility
Environmental governance	Oil-water separation, wastewater treatment	Superhydrophobic surface design
Energy and Electronics	New energy batteries, flexible electronics	Nanostructure regulation
Medical Health	Drug sustained release, tissue engineering	Biosafety verification

6. Conclusion

The development and application of hydrophobic nanocellulose not only solves the shortcomings of traditional nanocellulose ' overly hydrophilic ' , but also promotes its value transformation in many fields such as plastic reinforcement, environmentally friendly packaging, oil-water separation, energy electronics, and medical and health . With the deepening of green materials and sustainable development concepts, hydrophobic nanocellulose is expected to become a new generation of high-performance bio-based materials , with broad prospects for industrialization.