Amphiphilic H‐shaped block copolymers (PTMSPMA)2PEG(PTMSPMA)2 with 91 ethylene glycol (EG) units and four PTMSPMA chains have been synthesized by atom transfer radical polymerization of trimethoxylsilylpropyl methacrylate (TMSPMA) at room temperature in methanol. The structure, molecular weight, and molecular weight distribution have been characterized by 1H NMR spectroscopy and GPC traces. These H‐shaped block copolymers can self‐assemble in DMF/water, and multiple vesicle aggregates from large‐compound vesicles, to multilayer vesicles and unilamillar vesicles are formed. These morphologies can be simply controlled by variation of the chain length ratios.
