There is provided a novel chain-end functionalized PEO of formulas (I) to (IV) prepared via living anionic polymerization and chain-end functionalization, as well as a simple method of preparing nano-sized transition metal or metal salt particles using the same, which can be readily stabilized even in an aqueous medium. The water-soluble PEO-based polymers having various functional groups (including a drug group such as vitamin and anti-cancer agent) and the process of preparing nano-sized transition metal or metal salt particles using the same can be advantageously used in the development of new materials for drug delivering system and imaging, e.g., a contrast agent and an anti-cancer agent simultaneously.
