The preparation of a new surface-active sulfonated phosphine and its catalytic performance in aqueous biphasic hydroformylation of long chain olefins were reported. The amphiphilic phosphine: sodium salt of sulfonated n-C12H25O C6H4P(C6H4-p-CH3O)(2) (DMOPPS) was prepared by sulfonation of the hydrophobic phosphine DMOPP in concentrated H2SO4 under N-2 atmosphere at 30 degrees C for about 5 h. The rhodium complex, RhCl(CO)(TPPTS)(2) [TPPTS=P(C6H4-m-SO3Na)(3)], was used as the catalyst precursor. The catalytic active species with the DMOPPS as ligand was in situ formed by adding DMOPPS to the RhCl(CO)(TPPTS)(2) catalyst precursor. The surface-activity and micelle-forming property of this new amphiphilic phosphine were confirmed by using cryogenic transmission electron microscope (Cryo-TEM). Under the same conditions, the biphasic hydroformylation of I-decene using DMOPPS as ligand was compared with that using traditional TPPTS as ligand. The catalysis system using DMOPPS was also compared with the previous Rh-TPPTS-surfactant [C12H25N(CH3)(3)I (DTAI)] system. Some reaction parameters such as stirring rates, alkyl chain length of olefins, the molar ratio of phosphine/rhodium, and the catalyst recycle were also studied in detail. The results showed that the ligand DMOPPS exhibited a micelle-forming property that could significantly enhance the hydroformylation reaction rate of long chain olefin. Moreover, the surface-active phosphine may also stabilize the aqueous/oil phase boundary, which could enhance the biphasic catalytic reaction rates. (C) 2008 Elsevier B.V. All rights reserved.