Novel series of one-ended monooleate-modified poly(ethylene glycol) with active carboxylic terminal were synthesized by two steps of chemical modification of poly(ethylene glycol) by esterification, one with succinic anhydride to obtain active carboxylic terminal, and the other with oleic acid to obtain sufficiently hydrophobic terminal. The associative polymers were characterized by IR and H-1 NMR, their molecular weights were measured by gel permeation chromatography (GPC). The results showed that the synthesis procedure allows us to reach total grafting. The electron microscopy images, associative behaviour of the polymers in aqueous solution and their abilities to prolong the circulation time of emulsion in mice were also investigated. (c) 2006 Elsevier Ltd. All rights reserved.