Evaluating the Emulsifying Capacity of Cellulose Nanofibers Using Inverse Gas Chromatography

Cellulose nanofibers (CNFs) are attracting increasing attention as emulsifiers owing to their high emulsifying capacity, biocompatibility, and biodegradability. The emulsifying capacity has been experimentally shown to depend not only on the type of oil but also on the chemical structure of the CNF surface. However, the theoretical relationship between these two factors and emulsification remains unclear, and therefore, industrial applications are limited. Here, we assess the desorption energy (DE) of CNFs from the oil surface in o/w emulsion for various CNF/oil combinations to understand the mechanism of emulsification. Two types of surface-carboxylated CNFs having different cationic counterions, namely, sodium and tetrabutylammonium ions, were used as emulsifiers. The surface free energies of the CNFs were evaluated using inverse gas chromatography, and the nonpolar Lifshitz-van der Waals gamma LW, electron-acceptor gamma+, and electron-donor gamma- components were obtained from the chromatography profiles based on the van Oss-Chaudhury-Good theory. CNF with tetrabutylammonium ions was found to have a higher gamma+ component than CNF with sodium ions. Therefore, the emulsion stability improved with oils having high gamma- components owing to the increase in the DE value; this was verified through both theoretical calculations using a fibrous model and experimental dynamic interfacial tension measurements. Our approach is useful for predicting the emulsifying capacity of CNFs, and it should contribute toward the design of novel CNF-based emulsions.

Automated summary

Cellulose nanofibers (CNFs) are being studied for their potential as emulsifiers due to their high emulsifying capacity, biocompatibility, and biodegradability. This study aims to understand the mechanism of emulsification by evaluating the desorption energy of CNFs from the oil surface in o/w emulsion for different CNF/oil combinations. The results show that the emulsion stability improved with oils having high electron-donor components, which increase the desorption energy.