The water-soluble polymer, poly(enolate-co-vinyl alcohol-co-vinyl acetate) (PEW), prepared by controlled oxidation of poly(vinyl alcohol-co-vinyl acetate), is a valuable ligand for the rhodium biphasic catalytic hydroformylation of olefins. The average turnover frequency for the catalytic hydroformylation of 1-octene was 5.46 x 10(-5) kmol (kg(Rh)s)(-1) at 90 degrees C, and that of 1-dodecene was 2.36 x 10(-4) kmol (kg(Rh)s)(-1) at 60 degrees C. Selective hydroformylation of styrene and its derivatives gave up to 97% of branched-chain aldehyde using Rh-PVV under biphasic reaction conditions but at low conversions.