Living cationic polymerization of 4-methyl-7-(2-vinyloxyethoxy) coumarin (CMVE) was achieved using SnCl(4) in the presence of nBu(4)NBr as an added salt at 0 degrees C. The number-average molecular weight of the resulting polymers increased in direct proportion to the monomer conversion while retaining relatively low polydispersity. Structural analysis revealed that the resulting polymers carried pendant coumarinyl moieties. These coumarinyl moieties were crosslinked by irradiation with UV light at lambda(max) = 366 nm, and the crosslinked sites were then cleaved by irradiation with UV light at lambda(max) = 254 nm. The crosslinking behaviors of the polymers were studied by UV and FTIR spectroscopic measurement. PolyCMVE was soluble in dichloromethane but was found to be insoluble upon UV light irradiation. We also synthesized amphiphilic block polymers bearing coumarinyl moieties by living cationic copolymerization with an amphiphilic vinyl ether. The resulting block polymers were soluble in an aqueous medium and also formed micelle-like aggregates. Upon UV irradiation of aqueous solutions above the critical micelle concentration, an efficient crosslinking reaction occurred. Photoinduced structural changes of these polymer aggregates in the solution state were further investigated. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4701-4707, 2011