De-gassed water and surfactant-free emulsions: History, controversy, and possible applications

Recent reports claiming stabilisation of surfactant-free oil-in-water emulsions (o/w SFEMʹs) have intrigued the colloid science community, and been reported in both the scientific literature and popular press. Key to the formation of SFEMʹs is a sequence of solidification by freeze quenching, degassing by action of vacuum, then thawing, known as freeze-pump-thaw (F-P-T). It is believed that the “emulsification” is caused by a reduction of hydrophobic interactions owing removal of dissolved gas after these F-P-T cycles. This review summarises literature on SFEMʹs, covering experiments, proposed mechanisms, and some potentially exciting applications.