Hydrogenation of Styrene-Butadiene Rubber Catalyzed by Tris(triisopropylphosphine)hydridorhodium(I)

Abstract

The hydrogenation of C=C bonds in styrene−butadiene rubber (SBR), catalyzed by RhH(P(i-Pr)3)3, was experimentally investigated. Tris(triisopropylphosphine)hydridorhodium(I), RhH(P(i-Pr)3)3 (i-Pr=CH(CH3)2) was prepared by using rhodium chloride (RhCl3), tetrahydrofuran (THF), triisopropylphosphine (P(i-Pr)3) and a sodium mercury amalgam. The effect of catalyst/polymer ratio, reaction temperature, and hydrogen pressure on the reactivity of the catalytic system has been studied. The optimal experimental condition was obtained. The hydrogenated styrene-butadiene rubber (HSBR) was analyzed by FT-IR and 1H-NMR. In the absence of any additives, the conversion of C=C bonds in SBR could easily reach 95% in a short period of time, and no obvious cross-linking was observed. The dynamic properties of SBR did not change after the hydrogenation of the unsaturated C=C bonds. A preliminary reaction mechanism was also proposed. This study provides a new route, not only for the chemical modification of SBR by using a rhodium complex but also for the hydrogenation of other unsaturated polymers, such as diene-based rubbers.