Amphiphilic diblock copolymers were prepared by the living cationic polymerization of vinyl ethers in the presence of added bases, and their selective solvent-induced physical gelation behavior was investigated. The block copolymerization of 2-phenoxyethyl vinyl ether (PhOVE) and 2-methoxyethyl vinyl ether (MOVE) was carried out in the presence of ethyl acetate with Et1.5AlCl1.5 in toluene at 0 degreesC. Despite the rate difference, diblock copolymers with a very narrow molecular weight distribution were obtained, quantitatively. By adding the selective solvent, water, to the acetone solution of the diblock copolymer, PhOVE200-b-MOVE400, physical gelation occurred suddenly and the system ceased to flow, maintaining transparency. Viscoelastic measurements and transmission electron microscopic observations were performed to examine the characteristic gelation behavior and structure of the obtained gels. Various gelation conditions and physical gelation by other amphiphilic block copolymers were also designed on the basis of the solubility of each block segment. Further, new forms of physical gelation, accompanied by the solubilization of immiscible organic compounds, were achieved using similar diblock copolymers.