Heterogeneously Modified Cellulose Nanocrystals-Stabilized Pickering Emulsion: Preparation and Their Template Application for the Creation of PS Microspheres with Amino-Rich Surfaces

A kind of manipulative oil in water Pickering emulsion stabilized by heterogeneously modified cellulose nanocrystals (CNCs) and its application as a template for the creation of functional polystyrene microspheres were presented in this study. First, 18-carbon alkyl long chains were selectively introduced at the reducing ends of CNCs through a two-step chemical process including the hydrazone reaction and the amidation reaction. The as-obtained heterogeneously modified CNCs (CNC–C18) were then used as emulsifiers for the formation of oil in water Pickering emulsions. Compared with the pristine CNCs used in this study, CNC–C18 exhibited a high emulsifying performance. Highly stable oil in water Pickering emulsions could be formed at a low content of CNC–C18 nanoparticles. Because of the pH-responsive stability of the C═N bond linkages between 18-carbon alkyl chains and CNCs, the introduced 18-carbon alkyl chains could be cleaved completely at a suitable acid condition, and this endowed the formed Pickering emulsions with a pH-triggered de-emulsification character. Upon the replacement of n-hexane with a styrene/divinyl benezene mixed oil, cross-linked PS microspheres with amino-rich surfaces were created by the Pickering emulsion directed-radical copolymerization reaction, followed by acid treatment. The current work revealed CNCs could be used as a promising green and widely available resource for the fabrication of stimuli-responsive particle emulsifiers.