(363c) Anionic Hyperbranched Polyethylene Pickering Emulsifier's Synthesis and Its Application in High Internal Phase Emulsion

Pickering emulsifier attracts great research attention because it allows preparation of soap-free emulsion system, which eliminates the potentially detrimental effects of soap in subsequent applications. Furthermore, Pickering emulsifier exhibits resistance to coalescence and retains the basic properties of classical emulsions that are stabilized by surfactants. As organic particles, Pickering emulsifiers have unique advantages such as biocompatibility, biodegradability and anti-oxidizability. In this work, hyperbranched polyethylene (HBPE) with pendent-OH group was synthesized via catalyzed chain walking copolymerization of ethylene and 2-hydroxyethyl acrylate protected by trimethylsilyl group, with cationic Pd(II)-diimine as the catalyst. The resulting HBPE was subjected to treatment by NaH and 1,3-propanesultone to obtain sodium sulfonate HBPE, which can be used as an anionic Pickering emulsifier. This novel Pickering emulsifier can stabilize 83 wt% internal phase content in a W/O high internal phase emulsion (HIPE) system of styrene/divinyl benzene, by using 0.5 wt%-10 wt% emulsifier dosage relative to the oil phase. After polymerization of the oil phase, purification using Soxhlet extraction with water and methanol, and drying under reduced pressure, we obtained interconnected porous material with void and window diameter of 10 μm and 700 nm, respectively. The morphology of this material was analyzed by scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). This Pickering emulsifier has an added benefit of requiring significantly lower dosage to prepare interconnected porous materials than the conventional surfactants, with as low as 1 wt% Pickering emulsifier dosage needed compared to the required 20 wt% - 30 wt% of conventional surfactants.