The invention relates to novel demulsifiers for use in the demulsification of oils from water and vice versa, including the demulsification of crude oil from sea water or brine. In particular, the present invention relates to novel demulsifiers which are environmentally friendly, or ‘green’, and which can be used without restriction on-site in offshore oil drilling fields, for example in the North Sea. The novel demulsifiers are based on the reaction product of alkoxylated polyols or polyol esters with dicarboxylic acids.