, 04510 M exico DF, MexicoThis article reports the synthesis and characterization of four arm star-shaped poly(styrene-b-[(butadiene) 12x -(ethylene-co-butylene) x ]-b-styrene) (SBEBS) copolymers. A series of SBEBS copolymers with different compositions of the elastomeric block were produced by hydrogenating a given poly(styrene-b-butadiene-b-styrene) (SBS) copolymer using a catalyst prepared from bis(g 5 -cyclopentadienyl)titanium(IV) dichloride and nbutyllithium. The characterization was accomplished by proton nuclear magnetic resonance spectroscopy ( 1 H NMR), infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The results indicate that there is a selective saturation of the polybutadiene block over the polystyrene block; this selectivity was determined by the Ti/Li molar ratio and the concentration of Ti. It was observed that the saturation rate of the 1,2-vinyl was higher than that of the 1,4-trans and 1,4-cis poly(butadiene)-b isomers. The DSC and DMA results indicate that the degree of hydrogenation had a profound effect on the polymer's relaxation behavior. All samples exhibited a biphasic system behavior with two distinct transitions corresponding to the elastomeric and polystyrene blocks. SBEBS copolymers with higher saturation levels (>33%) exhibited a crystalline character. The TGA results indicated a characteristic weight loss temperature in all samples, with slightly higher thermal degradation stabilities in the materials with higher degrees of saturation.