C 2 -symmetric group 4 metallocenes based catalysts (rac-[CH 2 (3-tert-butyl-1-indenyl) 2 ]ZrCl 2 (1), rac-[CH 2 (1-indenyl) 2 ]ZrCl 2 (2) and rac-[CH 2 (3-tert-butyl-1-indenyl) 2 ]TiCl 2 (3)) are able to copolymerize styrene and 1,3-butadiene, to give products with high molecular weight. In agreement with symmetry properties of metallocene precatalysts, styrene homosequences are in isotactic arrangements. Full determination of microstructure of copolymers was obtained by 13 C NMR and FTIR analysis and it reveals that insertion of butadiene on styrene chain-end happens prevailingly with 1,4-trans configuration. In the butadiene homosequences, using zirconocene-based catalysts, the 1,4-trans arrangement is favored over 1,4-cis, but the latter is prevailing in the presence of titanocene (3). Diad composition analysis of the copolymers makes possible to estimate the reactivity ratios of copolymerization: zirconocenes (1) and (2) produced copolymers having r 1 × r 2 = 0.5 and 3.0, respectively (where 1 refers to styrene and 2 to butadiene); while titanocene (3) gave tendencially blocky styrene-butadiene copolymers (r 1 × r 2 = 8.5). The copolymers do not exhibit crystallinity, even when they contain a high molar fraction of styrene. Probably, comonomer homosequences are too short to crystallize (n s -16, in the copolymer at highest styrene molar fraction). © 2008 Wiley Periodicals, Inc.

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