Cosolvent effect on micelle formation of PEO PPO PEO block copolymer in aqueous solutions were studied by fluorescence probe method in the work. The cosolvents used included methanol(MOH)

ethanol(EOH)

1 propanol(POH)

2 methoxyethanol(ME)

ethylene glycol(EG)

ethanolamine(EA) and ethylenediamine(ED) that were introduced to the aqueous solution of block copolymers as a component of solvent. It was found that the introduction of some cosolvents which were compatible well with both water and PPO segments prevented the micelle formation and made the CMT increase

while other cosolvents were favorable for micelle formation and CMTdecreased.The cosolvents with difunctional group and smaller size were benefited for the formation of micelle with closed packaging unclei.It was also found

in condition that there was a little cosolvent introduced

the polarity of internal nuclei of micelle was mainly determined by the degree of packaging

but little relevant with the polarity of cosolvents.