The judicious choice of reaction conditions permitted living cationic polymerization of vinyl ethers with bulky and strongly interacting pendant groups, such as crystalline long alkyl chains and liquid crystalline mesogenic structures, using appropriate combinations of Lewis acids with added bases. Thus, well-defined random and block copolymers with various pendants were also synthesized. Highly sensitive UCST-type phase separation in various organic solvents was achieved employing crystallization of octadecyl pendants of homopolymers and random copolymers. This phase separation behavior is unusual for a polymer-organic solvent system. Furthermore, thermally induced reversible physical gelation was conducted using this then mosensitive behavior. These specific pendants were very effective not only in organic media but also in water, in obtaining hydrogels with relatively low polymer concentrations. (c) 2008 Wiley Periodicals, Inc.