11-12 February 2016 | Edinburgh
Speaker: Paul Clegg, University of Edinburgh
Time: 14:30 - 15:00
Location: St Trinnean's Room

Colloidal particles are often regarded as building blocks for creating new materials, so guiding them to form specific structures is crucial. In carefully chosen systems, observation of the assembly process is possible in real-time using fluorescence confocal microscopy. Here we assemble a cellular network starting from a colloid-stabilized emulsion of partially miscible liquids. Network formation is induced by the disappearance of the continuous phase via evaporation, a process that can be followed in detail [1]. The particles are driven into a cellular network as the droplets are squeezed together. Re-mixing of the liquid phases eventually occurs, leaving a stable structure surrounded by a single fluid phase. We relate this formation process back to the underlying phase behaviour of the partially miscible liquids.

We then apply our understanding to create a non-aqueous (oil-in-oil) Pickering high internal phase emulsion (HIPE) stabilized by chemically modified fumed silica [2]. In this case, a 75 vol % ethylene carbonate (EC)-rich internal phase is emulsified in 25 vol % p-xylene (xylene)-rich continuous phase using interfacial nanoparticles. Incorporating polystyrene (PS) into xylene enables one-step formation of PS-filled HIPEs in place of a multi-step polymerization of the continuous phase. Here, drying the pure HIPE results in the selective removal of xylene and coalescence of EC-rich droplets. By contrast, with the PS in the xylene-rich continuous phase, we show that EC-rich droplets can be retained even though the xylene is evaporated off, and a new semi-solid composite containing both liquid phase and solid phase is formed.


[1] N. Hijnen and P.S. Clegg, Mater. Horiz., 1, 360 (2014)

[2] D. Cai, J.H.J. Thijssen and P.S. Clegg, ACS Appl. Mater. Interfaces, 6, 9214 (2014)