Styrene/ethylene copolymerization was performed by Longo et al. with the use of a cyclopentadienyltitanium trichloride (CpTiCl3)/methylaluminoxane (MAO) system with various aluminuni/titanium ratios and various monomer compositions. The obtained polymer consisted of a mixture of an ethylene-styrene pseudorandom copolymer, polyethylene, and poly(styrene-block-ethylene) with a syndiospecific styrene-styrene unit (SPS-b-PE). In this work, from the whole polymer obtained with the CpTiCl3/MAO catalyst system, the SPS-b-PE copolymer was separated with the temperature rising elution fractionation method, and the structure was specified by C-13 NMR. The polymer obtained from the trivalent titanium catalyst, which was thought to be the active species of syndiotactic polystyrene, included both a styrene-styrene sequence and a styrene-ethylene-ethylene-styrene sequence. However, neither the styrene-ethylene-styrene sequence nor the long chain of polyethylene was included. (c) 2005 Wiley Periodicals, Inc.