CATALYTIC HYDROSILYLATION OF DIENE-BASED POLYMERS .2. HYDROSILYLATION OF STYRENE BUTADIENE COPOLYMER AND NITRILE BUTADIENE COPOLYMER

The hydrosilylation of styrene-butadiene copolymer (SBR) and nitrile-butadiene copolymer (NBR) using triethylsilane in the presence of RhCl(PPh3)3 was investigated at 110-degrees-C in toluene under Ar. The hydrosilylation products were characterized by IR and C-13 NMR. It was found that the reaction mechanism was markedly influenced by the nature of the functional groups in the polymer chain. In the case of SBR, the reaction occurred via a typical anti-Markovnikov addition leading to a linear adduct. However, when strong electronegative groups such as nitrile were present (i.e., in the case of NBR), the addition appeared to occur via a Markovnikov addition mechanism which led to a branched adduct. The styrene units in SBR appeared to retard the hydrosilylation, compared with pure polybutadiene, while the nitrile groups of NBR appeared to have less of an effect.