SANS measurements have been performed on the water-soluble PEO-PPO-PEO tri-block copolymer P85 [(EO)(26)(PO)(39)(EO)(26)] in presence of salt (KCl), alcohol (hexanol) and oil (benzene) in aqueous solution. The presence of additives entropically favors the dehydration of water from the PPO blocks similar to that increasing temperature and this leads to the micellization of block copolymers. The volume fraction and the size of the micelles increase with the increase in additive concentration. We have also examined the dependence of the micellization on the variation of. (a) ions of the salt, (b) length of the alcohol chain and (c) hydrophobicity of the oil. (c) 2006 Elsevier B.V. All rights reserved.