Search

This article reports the synthesis and characterization of four arm star-shaped poly[(styrene-b-[(butadiene).sub.1-x][(ethylene-co-butylene).sub.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([η.sup.5]-cyclopentadienyl)titanium(IV) dichloride and n-butyllithium. The characterization was accomplished by proton nuclear magnetic resonance spectroscopy (1H 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)-t) 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., INTRODUCTION Polymers containing conjugated dienes and vinyl aromatic monomers are extensively used for producing composite systems due to their interesting thermoplastic behavior and compatibility with a number of different materials [...]