Two representative bulk polymers, polyolefin (PO) and polystyrene (PS), were molecularly connected to form PO-block-PS by sequentially performing coordination and anionic polymerizations in one pot. Ethylene/1-octene copolymerization was performed using a typical ansa-metallocene catalyst, rac-[Me2Si(2-methylindenyl)](2)ZrCl2, in the presence of (benzyl)(2)zinc to grow PO-chains at the Zn site. Anionic styrene polymerization was subsequently performed using nBuLi(tmeda) (tmeda, N,N,N,N-tetramethylethylenediamine) initiator to consecutively grow PS-chains at the Zn site. The composition and the molecular weight of the PO-blocks were controllable depending on the feed amounts of 1-octene and (benzyl)(2)zinc (1-octene fraction: approximate to 20, approximate to 40 wt %; PO-M-w, 77,000-174,000) and the PS-block size was also controlled (PS-M-n, approximate to 21,000) with the complete conversion of the styrene monomer. Formation of block copolymers was evident in the GPC curves, TEM images, and strain-stress curves. (c) 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3110-3118