Interfacial regulation and visualization of Pickering emulsion stabilized by Ca2+-triggered amphiphilic alginate-based fluorescent aggregates

Abstract Pickering emulsions stabilized by soft particles have attracted increasing interest in research areas including food, pharmaceutics, and drug delivery. The interface-film properties have a great influence on the stability of Pickering emulsion. However, in situ studies of the stability of Pickering emulsions by direct visualization technology have not been well explored. In this work, a kind of amphiphilic alginate-based fluorescent polymer was synthesized (named Alg-TPVA) by Ugi reaction. The Alg-TPVA which can self-assemble into micellar aggregates in aqueous solution and was used to stabilize Pickering emulsion. The addition of Ca2+ triggered the gelation of Alg-TPVA aggregates and changed the properties of the oil-water interface. The size and morphology of the Pickering emulsion were studied in detail by optical scattering and microscopy analyses. The viscoelasticity of the interface-film was characterized by rheological test. The interface-film was further characterized in situ by confocal laser scanning microscope. The spatial network structure of the interface was observed by scanning electron microscope. Results showed that the Alg-TPVA aggregates can adsorb on the oil-water interface to form an interface-film that stabilizes the emulsion. When Ca2+ is 0.04 M, the interfacial viscoelasticity increases to the maximum, and the thickest interface-film formed rendered the best stability of Pickering emulsion. Moreover, the fluorescence-visualization technology can play a significant role in understanding emulsion stability.