Fully bio-based CO2-responsive pickering gel emulsions stabilized by cellulose nanocrystals combined with a rosin-based surfactant

Abstract

A CO2-responsive bio-based surfactant, N-decyl-maleimidepimaric acid N, N-dimethylenediamide bicarbonate (C10MPAN+), was synthesized from rosin. C10MPAN+ showed excellent CO2-responsive properties. Novel CO2-responsive soybean oil-in-water Pickering gel emulsions were further prepared using C10MPAN+ combined with cellulose nanocrystals (CNCs). Due to the strong hydrogen bonds and electrostatic interactions, C10MPAN+ could firmly absorb on the surface of CNCs. The C10MPAN+&CNCs could form a rigid shell on the water/oil interface, resulting in the stable Pickering emulsions. Demulsification could be easily achieved upon bubbling N2 into the emulsions. The microstructure, size distribution, viscoelasticity, and stability of the Pickering emulsions were investigated using a laser particle size analyzer, an optical microscope, and rheology. Emulsions prepared by C10MPAN+&CNCs showed no obvious coalescence or phase separation over 3 months. Importantly, Pickering gel emulsions were formed at C10MPAN+concentration higher than 1 mM. The viscoelasticities of the emulsions were enhanced with the increase of C10MPAN+ concentration and CNCs content. In addition, after five cycles of emulsification/demulsification by alternative bubbling CO2/N2, the Pickering gel emulsions exhibited less difference on the droplets size and viscoelasticity. This work provides a fully bio-based responsive Pickering gel emulsion, and promotes the exploitation and utilization of biomass resources.