A relatively simple way of obtaining highly stable W/O emulsions is to use block copolymers such as PEG-45 dodecyl glycol copolymer. These products, with molecular weights of 2000 to 4000, can improve the stability of W/O emulsions by protection of the droplets from coalescence. The hydrophilic middle part is responsible for a good anchorage in the water phase, while the highly branched ends give a steric hindering effect. The high molecular weight imparts excellent skin compatibility. Contrary to other stabilizers, for example metal soaps, which increase the viscosity of the outer emulsion phase, these copolymers typically reduce the viscosity. It is possible to obtain light, highly stable W/O lotions that are good bases for sun preparations and which give a skin-feel very close to emulsions.
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