Hydrogenation of polystyrene-b-polybutadiene-b-polystyrene block copolymers using a metallocene/n-butyllithium catalyst - the role of n-butyllithium

A metallocene catalyst system, primarily the bis(eta(5)-cyclopentadienyl)co balt (Cp2Co) combined with n-butyllithium (n-BuLi), was found to be active for the hydrogenation of polystyrene-b-polybutadiene-b-polystyrene (SBS) bl ock copolymer. Data from the UV spectroscopy of the catalyst system indicat ed that one of the Cp ligand in the original Cp2Co was substituted by the b utyl group forming a CpCoBu as the major catalytic species. The kinetics of the hydrogenation reaction were studied by monitoring the extent of satura tion of double bonds on the polybutadiene segment of the copolymer using FT IR spectroscopy. The temperature dependence of the hydrogenation rate was a nalyzed and the activation energy was determined as 14.11 kcal/mol of the d ouble bond. (C) 1999 Elsevier Science Ltd. All rights reserved.