Polymeric Surfactant (PIBSA-X) Facilitates the Formation of a Water-in-Oil Emulsion Reactor for the Preparation of Ultrasmall Nanosilica

Despite the widespread application of ultrasmall nanosilica, solving its aggregation problem during the preparation process remains a challenge. In this paper, ultrasmall nanosilica with a controllable size and aggregates were prepared through the water-in-oil (W/O) emulsion method by using polyisobutylene succinic anhydride-type polymeric surfactants (PIBSA-X) as an isolating agent. PIBSA-X polymeric surfactants with different hydrophilic groups were prepared using industrial-grade PIBSA, which can form stable W/O-type emulsions well. Subsequently, the W/O-type emulsion droplets were used as reactors and tetraethyl orthosilicate was hydrolyzed under ammonia alkaline conditions to synthesize ultrasmall nanosilica (10 nm). Furthermore, the morphological evolution of nanosilica aggregates can be tuned by varying the oil/water ratio, which controls the emulsion droplets. A possible mechanism is proposed to explain why the emulsion method approach affords nanosilica aggregates with various morphologies and pellet size in water-in-oil (W/O-type) emulsion droplets. This study provides a precise and simple synthetic method for the development of ultrasmall nanosilica, which has good potential to be industrialized.