Anionic polymerizations of 2-methoxyethyl methacrylate (1), 2-(2-methoxyethoxy)ethyl methacrylate (2), and 2- [2-(2-methoxyethoxy)ethoxy]ethyl methacrylate (3) were carried out with 1,1-diphenyl-3-methylpentyllithium/lithium chloride and diphenylmethylpotassium/diethylzinc in THF at -78 degreesC for 2-4 h. The resulting polymers possessed the predicted molecular weights based on the molar ratios between monomers to initiators and the narrow molecular weight distributions (M-w/M-n < 1.1). The stability of the propagating chain ends of poly(2) and poly(3) was confirmed by the quantitative efficiency in the reversible sequential block copolymerizations between 2 and 3. New block copolymers having well-defined chain structures, poly(2)-block-poly(3), poly(3)-block-poly(2), polystyrene-block-poly(1), polystyrene-block-poly(2), and polystyrene-block-poly(3), were anionically synthesized. Both the solubility and the cloud point of polymers strongly depended on the length of hydrophilic oligo(ethylene glycol) unit. Poly(2) and poly(3) with longer oligo(ethylene glycol) chains were readily soluble in water, whereas poly(1) was insoluble in water. The aqueous solutions of poly(2) and poly(3) showed the reversible cloud points at 26 and 52 degreesC, respectively.