Stimuli-responsive Pickering emulsions: recent advances and potential applications

Abstract

Pickering emulsions possess many advantages over traditional surfactant stabilized emulsions. For example, Pickering emulsions impart better stability against coalescence and, in many cases, are biologically compatible and environmentally friendly. These characteristics open the door for their use in a variety of industries spanning petroleum, food, biomedicine, pharmaceuticals, and cosmetics. Depending on the application, rapid, but controlled stabilization and destabilization of an emulsion may be necessary. As a result, Pickering emulsions with stimuli-responsive properties have, in recent years, received a considerable amounts of attention. This paper provides a concise and comprehensive review of Pickering emulsion systems that possess the ability to respond to an array of external triggers, including pH, temperature, CO2 concentration, light intensity, ionic strength, and magnetic field. Potential applications for which stimuli-responsive Pickering emulsion systems would be of particular value, such as emulsion polymerization, enhanced oil recovery, catalyst recovery, and cosmetics, are discussed.

In vitro digestion of Pickering emulsions stabilized by soft whey protein microgel particles: influence of thermal treatment

“…For instance, if the contact angle is smaller than 90 , particles are more wetted by the continuous phase in an O/W emulsion rather than the oil phase. Although the stabilization of colloids using particles at the interface was proposed a century ago by Ramsden 1 and proven four years later experimentally by Pickering 2 , there has been a renewed upsurge of research interest, illustrated by the growing number of reviews in the last few years [3][4][5][6][7][8][9][10] . This is largely due to the demand for highly stable emulsions and the growing requirements for biocompatible surfactant--immediately suitable for use in food, pharmaceutical, cosmetics, agrochemicals and other allied soft matter applications.…”

CO2/N2 triggered switchable Pickering emulsions stabilized by alumina nanoparticles in combination with a conventional anionic surfactant

“…6 It is obvious that the formation of switchable or stimuliresponsive emulsions relies on developments in the corresponding particulate stabilizers, which can be transformed between surface-active and surface-inactive via appropriate triggers. 5,6 For this purpose particles have to be coated or grafted with functional groups which can be transformed between hydrophilic and lipophilic in response to appropriate triggers.…”

“…5,6 For this purpose particles have to be coated or grafted with functional groups which can be transformed between hydrophilic and lipophilic in response to appropriate triggers. 6 Currently several triggers have been developed, including light irradiation, 7-10 CO 2 /N 2 , 11-14 temperature, [15][16][17] pH, 18-24 redox, 25,26 magnetic eld, 27,28 and dual triggers like pH-temperature, 29,30 light-temperature 31 and magnetic eld intensity-temperature.…”

“…6 These triggers however are convenient to achieve with a variety of suitable chemicals. Light irradiation is environmentally benign, but the efficiency of demulsication may be signicantly inhibited by the turbidity or opacity of the emulsions.…”

Calcium phosphate substrates with emulsion-derived roughness: Processing, characterisation and interaction with human mesenchymal stem cells

“…Recent advances demand greater functional control from them, such as the ability to control the rheology for extrusion [7] or to respond to external stimuli [8]. Different stimuli such as temperature [3], CO2 [8], magnetic fields [9], salt concentration [10] and light intensity [11] have been used. pH is another very commonly used external trigger.…”