A series of poly(2-methoxyethyl vinyl ether)s with narrow molecular weight distributions and with perfectly defined end groups of varying hydrophobicities was successfully synthesized by base-assisting living cationic polymerization. The end group was shown to greatly affect the temperature-induced phase separation behavior of aqueous solutions (lower critical solution temperature-type phase separation) or organic solutions (upper critical solution temperature-type phase separation) of the polymers. The cloud points were also influenced largely by the molecular weight and concentration of the polymer. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012