Stabilisation of surfactant-free emulsions

Nanoemulsions are usually used as impregnating emulsions for moisturised tissues, while microemulsions are emerging for the preparation of oily cleansing agents. Although confusing information is reported when comparing the difference in particles’ size between nanoemulsions and microemulsions, the major difference relies on the thermodynamic stability: nanoemulsions are thermodynamically unstable, whereas microemulsions are thermodynamically stable.² Although these innovations are very attractive, cosmetic markets still rely on conventional emulsions for personal care fundamentals for the formulation of cosmetic products such as body lotions, skin creams, and sunscreens. 

One of the most important properties for industrial formulations is the emulsion’s stability.³ Therefore, Pickering emulsions,^4,5 stabilised by solid particles, have gained interest due to their surfactant-free character and their numerous practical applications.⁶ A large variety of natural and synthetic particles have been reported as film-formers and Pickering emulsion stabilisers. The most commonly used inorganic natural particles are smectites⁷ and high purity natural clays such as sodium/calcium bentonites.⁸ Layered double hydroxides (LDH) were also used to stabilise paraffin oil-in-water (O/W) emulsions.⁹

Herein, we report on the design of new amphiphilic organosilicates EBISilc with the adjusted ratio of hydrophilic and lipophilic organosilanes. Compared with the conventional synthesis of organosilicate first described by Fukushima and Tani10 as a one-pot sol-gel inspired reaction under mild conditions, our team developed a process introducing a doublefunctionalisation. We obtained organicinorganic hybrids with a tailored hydrophilic/hydrophobic ratio and which include both aluminium and calcium within the inorganic interlayer space (Fig. 1).^11,12