The anionic polymerization of ethoxyethyl glycidyl ether (EEGE) initiated by cesium alkoxide was studied. The ring‐opening polymerization of EEGE in the presence of cesium alkoxide of 1‐methoxy‐2‐ethanol does not involve any side reactions. The presence of an additional alcohol leads to a significant increase of the initiator efficiency.

Aqueous solutions of poly (ethoxyethyl glycidyl ether) (PEEGE) exhibit lower critical solution temperature (LCST), and the polymer solubility in water is extremely sensitive to its MW. Two novel types of block copolymers based on PEEGE were synthesized: triblock‐copolymers of ABA (A′:BA′) structure, where A is the PEEGE block, A′ polyglycidol (PG) and B the polypropylene oxide (PPO) block, and A₂S (A′₂S) and A₄S (A′₄S) heteroarm stars, where S is the polystyrene block.

The synthesis of the ABA block was performed by polymerization of EEGE initiated by bi‐functional PPO/Cesium alkoxide macroinitiator. The PEEGE blocks were converted into PG blocks by successful cleavage of the ethoxyethyl group.

Polystyrene/PEEGE and polystyrene/PG three‐ and five‐ heteroarm star copolymers were synthesized by a coupling reaction between well‐defined chain‐end‐functionalized polystyrenes carying dendritic benzyl bromide moieties with living anionic polymers of PEEGE with one cesium alkoxide terminal group. The coupling reaction proceeds quantitatively without any side reactions, and thus series of star‐branched polymers can be systematically synthesized. Polystyrenes with two or four PG arms have been obtained after the cleavage of the protecting group. The compact structure of these multi‐arm star polymers and their amphiphilic character leads to the formation of nanoparticles in aqueous solution with rather uniform size distribution and a mean diameter of 15 nm.