Interfacial characteristics of block copolymer micelles stabilized Pickering emulsion by confocal laser scanning microscopy

Hypothesis: Novel Pickering emulsions stabilized by self-assembled nano-objects of amphiphilic copolymers are attractive in many applications. However, it is not clear to what extent those nano-objects could stay at the oil/water interface. Owing to the twisted intramolecular charge transfer state (TICT) property of Nile red, the distinguishable fluorescent characteristics of Nile red dissolved in n-dodecane and solubilized in copolymer micelles benefit the investigation of the oil/water interfacial nature of Pickering emulsions in situ. Experiments: Two amphiphilic diblock copolymers PNMP53-b-PFMA(5) and PNMP53-b-PFMA(10) named poly (N-(2-methacryloylxyethyl) pyrrolidone)-block-poly(2-(perfluorooctyl) ethyl methacrylate) were synthesized, they can form spherical and wormlike micelles in water spontaneously, respectively. Oil in water (O/W) emulsions were generally produced at different conditions by employing these copolymer micelles as emulsifiers. The size and morphology of prepared emulsions were studied by light scattering and microscope techniques in detail. Moreover, the effect of emulsification conditions on the interfacial morphology evolution of prepared emulsions were characterized systematically in situ by the proposed method based on the confocal laser scanning microscopy (CLSM) measurements. Findings: We clarified the progressive transition from Pickering emulsions to classic emulsions through the sustained changes of emulsification conditions by the developed CLSM method, in which block copolymer monomers and their assemblies were played as emulsifiers to stabilize emulsion droplets synergistically. Generally speaking, Pickering emulsions were produced in the presence of sufficient micelles at low emulsification shear rates. Otherwise, common emulsions stabilized by block copolymer monomers would be formed. (C) 2019 Elsevier Inc. All rights reserved.