A series of novel hyperbranched multiarm copolyethers of PEHO-star-PPO with different molar ratios of PPO arms to PEHO cores (R-A/C) were synthesized. NMR and SEC measurements confirm the molecular structure of PEHO-star-PPOs. Both glass transition temperature (T-g) and decomposition temperature (T-d) of PEHO-star-PPO decrease with increasing R-A/C. The self-assembly behavior of PEHO-star-PPO copolymers was investigated by TEM, SEM, DLS, etc. The results indicate that the ill-defined PEHO-star-PPO molecules could aggregate into large spherical micelles (over 100 nm) with controlled sizes, and the micelle size decreases as R-A/C increases. The structure of the large micelles was explored by FT-IR, NMR, etc. Accordingly, a possible self-assembly process is put forward, and a new aggregate model termed as multimicelle aggregate (MMA) (Figure 9C) is suggested to explain the formation of the large micelles. In MMA model, the large micelles are the aggregates of small micelles associated by intermicellar interactions such as hydrogen bonds.