Influence of high intensity ultrasonication on the fabrication of poly(lactic-co-glycolic acid)/ chitosan nanocomposites based on pickering emulsions

Previously, by introducing High intensity ultrasonication (HIU) technique into Pickering emulsions, a modified Pickering emulsions is proposed by our group to facilely fabricate biodegradable composite nanospheres with narrow size distribution. In this study, in order to further study the influence of HIU in Pickering emulsions on the formation of monodisperse nanospheres, comparisons between HIU-assisted and non-HIU-assisted emulsions stabilized by chitosan colloids based on different initial molecular weight were conducted. It was found that in non-HIU-assisted emulsions, no matter the difference of the molecular weight of the used stabilizers, microcapsules were formed instead of nanospheres. Moreover, in contrast to the obtain of monodisperse nanospheres from HIU-assisted emulsions, it was observed that the sizes of the resulting microcapsules are widely distributed. The illustration of the solidification process of solvent evaporation further revealed the formation of microcapsules based on non-HIU-assisted emulsions. The results therefore suggest that the assistance of HIU as a generator of strong shear force is effective in reducing emulsion droplet sizes as well as improving monodispersity and without the assistance of HIU, the formation of hollow structure can be led within larger emulsion droplets due to the deposition of the polymer crust on the wall of stabilizers as outer coating.