Wetting and emulsification properties of cellulose nanocrystals modified with tannic acid and alkyl cellulose derivatives

Hypothesis: Cellulose nanocrystals (CNCs) are sustainable rod-like nanoparticles that can be used to stabilize oil-in-water emulsions and can create hydrophilic coatings. Modifying the surface of CNCs can improve emulsion properties and allow for adjustable wettability.

Experiments: This study explores the improvement of Pickering emulsion properties for various oils and the adjustability of coated surfaces through the physical modification of CNCs, without chemical functionalization. Bio-based additives, including antioxidant tannic acid (TA), methyl cellulose (MC), and ethyl cellulose (EC) were used as surface modifiers. The identification of optimal formulations involved varying the weight fraction of the alkyl cellulose derivatives.

Findings: The findings suggest that, akin to pure CNCs, Pickering emulsions stabilized by TA and/or MC-modified CNCs demonstrate comparably high stability. The introduction of MC at a low weight fraction enhances hydrophilicity, and AFM analysis reveals smooth surfaces, mitigating the potential influence of roughness. In contrast, EC-modified CNCs result in less stable emulsions but exhibit more hydrophobic surfaces. This translates to a broad spectrum of characteristics, ranging from quasi-superhydrophilic to nearly hydrophobic (with contact angles spanning from below 11° up to 68°), all controllable through a straightforward physical coating process. This facile preparation of coated CNCs provides a versatile approach to customizing the wetting and emulsification properties of nanomaterials.