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The topology effects of cyclization on thermal phase transition behaviors were investigated for a series of amphiphilic Pluronic copolymers of both hydrophilic-hydrophobic-hydrophilic and hydrophobic-hydrophilic-hydrophobic block sequences. The dye solubilization measurements revealed the lowered critical micelle temperatures (T-CMT) along with the decreased micellization enthalpy (Delta H-mic) and entropy (Delta S-mic) for the cyclized species. Furthermore, the transmittance and dynamic light scattering (DLS) measurements indicated a block sequence-dependent effect on the clouding phenomena, where a profound decrease in cloud point (T-c) was only found for the copolymers with a hydrophilic-hydrophobic-hydrophilic block sequence. Thus, the effect of cyclization on these critical temperatures was manifested differently depending on its block sequence. Finally, a comparison of the linear hydroxy-terminated, methoxy-terminated, and cyclized species indicated the effect of cyclization to be unique from a simple elimination of the terminal hydrophilic moieties.