The potential of magnetic heating for fabricating Pickering-emulsion-based capsules

Rafał Bielas,Dawid Surdeko,Katarzyna Kaczmarek,Arkadiusz Józefczak

doi:10.1016/j.colsurfb.2020.111070

Abstract

Pickering emulsions (particle-stabilized emulsions) have been widely explored due to their potential applications, one of which is using them as precursors for the formation of colloidal capsules that could be utilized in, among others, the pharmacy and food industries. Here, we present a novel approach to fabricating such colloidal capsules by using heating in the alternating magnetic field. When exposed to the alternating magnetic field, magnetic particles, owing to the hysteresis and/or relaxation losses, become sources of nano- and micro-heating that can significantly increase the temperature of the colloidal system. This temperature rise was evaluated in oil-in-oil Pickering emulsions stabilized by both magnetite and polystyrene particles. When a sample reached high enough temperature, particle fusion caused by glass transition of polystyrene was observed on surfaces of colloidal droplets. Oil droplets covered with shells of fused polystyrene particles were proved to be less susceptible to external stress, which can be evidence of the successful formation of capsules from Pickering emulsion droplets as templates.

Highlights

Colloidal capsules have become the emerging class of structures due to their applications, mainly in the pharmaceutical industry [1], where they may provide great possibilities for controlled release of capsulated species [2,3]
In order to show the efficiency of heating induced by magnetic particles in an external magnetic field, we investigated such low-concentrated Pickering emulsions (10% silicone oil to castor oil mass ratio) stabilized with both polystyrene and magnetite particles, and compared them with corresponding pre-emulsions exposed to the same conditions
We showed that under alternating magnetic field magnetite particles acted as a good heat source in both Pickering emulsions and suspensions

Summary

Introduction

Colloidal capsules have become the emerging class of structures due to their applications, mainly in the pharmaceutical industry [1], where they may provide great possibilities for controlled release of capsulated species [2,3]. There are several routes for fabricating colloidal capsules from particle-stabilized emulsions (Pickering emulsions), including the use of polyelectrolyte complexation on the particle layers [4], gel trapping [5], polymerization [6] or sintering [7]. An important factor here is the glass transition temperature (Tg). This value particles can fuse without being completely melted [8]. Other factors, such as time of sintering and particle concentration, should be taken into account [9]. We propose the potential new technique of production of colloidal capsules from oil-in-oil Pickering emulsions by using magnetic particles in the alternating magnetic field

Methods

Results

Discussion

Conclusion