Stimuli-responsive gradient copolymers, composed of various monomers, were synthesized by living cationic polymerization in the presence of base. The monomers included thermosensitive 2-ethoxyethyl vinyl ether (EOVE) and 2-methoxyethyl vinyl ether (MOVE), hydrophobic isobutyl vinyl ether (IBVE) and 2-phenoxyethyl vinyl ether (PbOVE), crystalline octadecyl vinyl ether (ODVE), and hydrophilic 2-hydroxyethyl vinyl ether (HOVE). The synthesis of gradient copolymers was conducted using a semibatch reaction method. Living cationic polymerization of the first monomer was initiated using a conventional syringe technique, followed by an immediate and continuous addition of a second monomer using a syringe pump at regulated feed rates. This simple method permitted precise control of the sequence distribution of gradient copolymers, even for a pair of monomers with very different relative monomer reactivities. The stimuli-responsive gradient, block and random copolymers exhibited different self-association behavior. (C) 2008 Wiley Periodicals, Inc.