Copolymerization of ethylene with styrene, catalyzed by 1,4-dithiabutanediyl-linked bis(phenolato) titanium complex and methylaluminoxane, produced exclusively ethylene-styrene copolymers with high activity. Copolymerization parameters were calculated to be r(E) = 1.2 for ethylene and r(S) = 0.031 for styrene, with r(E) r(S) = 0.037 indicating preference for alternating copolymerization. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with styrene content up to 68%. The copolymer microstructure was fully elucidated by C-13 NMR spectroscopy revealing, in the copolymers with styrene content higher than 50%, the presence of long styrene-styrene homosequences, occasionally interrupted by isolated ethylene units. (c) 2006 Wiley Periodicals, Inc.