Two new L-cysteine-derived zwitterionic arnphiphiles with poly(ethylerie glycol) methyl ether (mPEG) tail of chain ain lengths were synthesized and their surface activity and self-assembly p r operties were investigated. Inaeqs eo phosphate buffered solution of pH 7.0, the am hi aqueous P observed to form stable unilamellar vesicles, the bllayer membrane of which is constituted by the inPEG chains. The vesicle phase was characterized, by a number of methods including fluorescence spectroscopy, dynamic light scattering, and transmission also studied nthaepyd b change (aHo elseetctroni microscopy. The thermodynamics of self-assembl y w yisaothermaltitration the standard Gibbs free energy change (G m), st n d a m) an d micellization. The self-assembly process was found to be entropy-driven, which implies on taitof conentional surfa t hydrocar c ants. The effects of pH temperature salt d aging investigated. Encapsulation,ana 'pH-triggered release of model hydrophobic and and ay h and calorimetry through measurements standard entropy change (Als that the mPEG.chgn behaves like time on the bilayer stabilitrveretals ic drugs is demonstrated.