Novel vinyl polymers bearing monoazacrown ether-type side chains with a number average molecular weigh of over 5000 were radically synthesized from the 16-membered alpha-methylenemacrolide monomers. The obtained polymers possessed a Na+ or K+ selective extraction ability, whereas K+ was preferentially extracted by the monomers. The polymer having the N-(2- naphthoyl) azacrown ether pendant groups showed a selective UV-responsive complexation with Li+ in 1,2-dichloroethane-CH3CN.