An anionic inverse emulsion thickener which imparts an extremely short flow to a wide variety of aqueous and non-aqueous compositions and is effective over a wide pH range. Supplied as an easy to use, low viscosity liquid which gives an instantaneous thickening effect on direct mixing into the composition. The polymer in is already in solution (as the ammonium salt) and not requiring any other additives to promote thickening e.g. alkali, surfactant etc. APEO free.