Boronate-polyol networks reinforce cellulose-stabilized Pickering emulsions

Sodium carboxymethyl cellulose (CMC-Na) always serves as a thickening agent and secondary stabilizer in emulsions. In this paper, a boronate-modified CMC-Na (CMC-B) and its derivative were synthesized. Compared with CMC-Na, CMC-B could effectively stabilize O/W Pickering emulsions alone in alkaline environments. Furthermore, the emulsification performance of CMC-B was significantly enhanced by incorporating polyhydroxy macromolecules such as tannic acid (TA) through the formation of boronate-polyol groups. High-internal-phase O/W Pickering emulsions (HIPEs, V_oil > 80 %) were achieved by the composite of CMC-B and TA (0.1 wt%, CMC-B-TA) at pH 8.0-11.0. The dynamic boronate-polyol linkages strengthened the cellulose network in the emulsions. This effect was applicable to various oil phases, as well as composites of CMC-B with other polyhydroxy compounds (e.g., polysaccharides and polyphenols). The salt tolerance and antioxidative capacity were also enhanced in the emulsions stabilized by CMC-B-TA. In contrast to the complex procedures required for the preparation of cellulose nanocrystals or nanofibers, this strategy employed a straightforward method to modify commercially available CMC-Na with boronate groups, yielding multifunctional emulsions that demonstrated both alkali resistance and antioxidant properties.