Polyepichlorohydrin containing reactive chloromethyl side groups was found to be highly soluble in polar ionic liquids containing halide anions such as 1-n-butyl-3-methyl imidazolium chloride, 1-n-ethyl-3-methyl imidazolium bromide, and 1-n-hexyl-3-methyl imidazolium chloride, whereas it was insoluble in less polar ionic liquids such as 1-n-butyl-3-methyl imidazolium tetrafluoroborate and 1-n-butyl-3-methyl imidazolium hexafluorophosphate. The reaction of polyepichlorohydrin with thiolates and thiol compounds in the polar ionic liquids as reaction media produced polyoxyethylenes with thioether side groups in very high conversions and yields. When polyepichlorohydrin was reacted with sodium 1H,1H,2H,2H-perfluorinated decanethiolate in 1-n-hexyl-3-methyl imidazolium chloride at 70 degrees C and the product was separated through centrifugation, the ionic liquid could be used more than four times, and high conversions (>70 mol %) and yields (>62 wt %) were maintained. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 132-138,2009