Understanding demulsification in pickering emulsions

Lead Research Organisation: University of Leeds
Department Name: Chemical and Process Engineering


Pickering emulsions are dispersions of two immiscible fluids of any type either oil-in-water (o/w), water-in-oil (w/o) stabilized by solid particles instead of molecular surfactants. They possess ultrastability due to strong particle adsorption at the fluid-fluid interface with high desorption energies. These emulsions can be stabilized by microgel particles, that could be either made of synthetic polymers like poly-(N-isopropylacrylamide) (pNIPAM) or biocompatible microgels made by the physical crosslinking of various animal and plant proteins. Because of their ultra-stability, often these particles are difficult to desorb unless external stimuli or forces are applied. Nevertheless, demulsification is important to allow release of actives or hydrophobic nutrients from the internal (emulsified) droplets, which has attracted relatively little attention in literature.

The aim of this review is to understand the factors affecting demulsification in Pickering emulsions, particularly fabricated using synthetic polymeric particles to inform future demulsification in emulsions stabilized by biocompatible particles. From the detachment energy theories, the variation of the force with displacement is largely governed by the interfacial tensions between the fluids, the wettability and the particle size [1]. Preliminary findings suggest that even though the adhesion of particles to a surface can be strong and appear irreversible in many situations, it is possible to cause desorption or detachment of these particles through the application of a suitable external field. A range of physical conditions (pH, temperature, heat, shearing) or mixing with additives (surfactants, enzymes, salts, bacteria) have been used in literature to demulsify Pickering emulsions. There is significant research in this area on synthetic particles, however, there are still uncertainties regarding the mechanisms that trigger demulsification. In contrast, there is very limited research on demulsification of biocompatible particles.

Having a better understanding of the factors that influence demulsification can help unlock the full potential of Pickering emulsions and its many applications such as the release of active ingredients in the chemical, food, and pharmaceutical industries.

Planned Impact

The CDT in Molecules to Product has the potential to make a real impact as a consequence of the transformative nature of the underpinning 'design and supply' paradigm. Through the exploitation of the generated scientific knowledge, a new approach to the product development lifecycle will be developed. This know-how will impact significantly on productivity, consistency and performance within the speciality chemicals, home and personal care (HPC), fast moving consumer goods (FMCG), food and beverage, and pharma/biopharma sectors.
UK manufacturing is facing a major challenge from competitor countries such as China that are not constrained by fixed manufacturing assets, consequently they can make products more efficiently and at significantly lower operational costs. For example, the biggest competition for some well recognised 'high-end' brands is from 'own-brand' products (simple formulations that are significantly cheaper). For UK companies to compete in the global market, there is a real need to differentiate themselves from the low-cost competition, hence the need for uncopiable or IP protected, enhanced product performance, higher productivity and greater consistency. The CDT is well placed to contribute to addressing this shift in focus though its research activities, with the PGR students serving as ambassadors for this change. The CDT will thus contribute to the sustainability of UK manufacturing and economic prosperity.
The route to ensuring industry will benefit from the 'paradigm' is through the PGR students who will be highly employable as a result of their unique skills-set. This is a result of the CDT research and training programme addressing a major gap identified by industry during the co-creation of the CDT. Resulting absorptive capacity is thus significant. In addition to their core skills, the PGR students will learn new ones enabling them to work across disciplinary boundaries with a detailed understanding of the chemicals-continuum. Importantly, they will also be trained in innovation and enterprise enabling them to challenge the current status quo of 'development and manufacture' and become future leaders.
The outputs of the research projects will be collated into a structured database. This will significantly increase the impact and reach of the research, as well as ensuring the CDT outputs have a long-term transformative effect. Through this route, the industrial partners will benefit from the knowledge generated from across the totality of the product development lifecycle. The database will additionally provide the foundations from which 'benchmark processes' are tackled demonstrating the benefits of the new approach to transitioning from molecules to product.
The impact of the CDT training will be significantly wider than the CDT itself. By offering modules as Continuing Professional Development courses to industry, current employees in chemical-related sectors will have the opportunity to up-skill in new and emerging areas. The modules will also be made available to other CDTs, will serve as part of company graduate programmes and contribute to further learning opportunities for those seeking professional accreditation as Chartered Chemical Engineers.
The CDT, through public engagement activities, will serve as a platform to raise awareness of the scientific and technical challenges that underpin many of the items they rely on in daily life. For example, fast moving consumer goods including laundry products, toiletries, greener herbicides, over-the-counter drugs and processed foods. Activities will include public debates and local and national STEM events. All events will have two-way engagement to encourage the general public to think what the research could mean for them. Additionally these activities will provide the opportunity to dispel the myths around STEM in terms of career opportunities and to promote it as an activity to be embraced by all thereby contributing to the ED&I agenda.


10 25 50

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S022473/1 01/04/2019 30/09/2027
2746347 Studentship EP/S022473/1 01/10/2022 30/09/2026 Gloria Hernandez Rodriguez