Amphiphilic nature
Emulsifiers are typical amphiphilic compounds with polar or hydrophilic (i.e. water-soluble) moieties and non-polar (i.e. hydrophobic or lipophilic) moieties. Emulsifiers that are more soluble in water (on the contrary, less soluble in oil) usually form oil in water lotion, while emulsifiers that are more soluble in oil will form water in oil lotion.
Influence on stability of lotion
Emulsifier can increase the stability of lotion through various mechanisms during the emulsification process. For example, by reducing the interfacial tension between two phases (surface tension theory); Forming a thin film on a phase to form mutually repulsive small balls (repulsion theory); Emulsifiers (hydrocolloids) such as arabic gum and tragacanth gum, as well as PEG (or polyethylene glycol), glycerol, and other polymers (such as CMC carboxymethyl cellulose), maintain the stability of dispersed phase microspheres in suspension by increasing the viscosity of the medium (viscosity modification).