Two representative bulk polymers, polyolefin (PO) and polystyrene (PS), were molecularly connected to form POblock-PS by sequentially performing coordination and anionic polymerizations in one pot. Ethylene/1-octene copolymerization was performed using a typical ansa-metallocene catalyst, rac-[Me 2 Si(2-methylindenyl)] 2 ZrCl 2 , in the presence of (benzyl) 2 zinc to grow PO-chains at the Zn site. Anionic styrene polymerization was subsequently performed using nBuLiÁ(tmeda) (tmeda, N,N,N 0 ,N 0 -tetramethylethylenediamine) initiator to consecutively grow PS-chains at the Zn site. The composition and the molecular weight of the PO-blocks were controllable depend-ing on the feed amounts of 1-octene and (benzyl) 2 zinc (1octene fraction: $20, $40 wt %; PO-M w , 77,000-174,000) and the PS-block size was also controlled (PS-M n , $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.