The living, isoselective polymerization of 4-methyl-1,3-pentadiene, 4-methylstyrene, and 4-tert-butylstyrene was promoted by using the titanium complex 1 activated by methylaluminoxane (MAO) at room temperature producing highly isotactic polymers. The synthesis of highly isotactic polystyrene-block-poly(4-methyl-1,3-pentadiene), poly(4-methylstyrene)-block- polystyrene, poly(4-methylstyrene)-block-1,4-trans-poly(1,3-butadiene), poly(4-methylstyrene)-block-polystyrene-block-poly(4-methylstyrene), poly(4-methylstyrene)-block-polystyrene-block-poly(4-methyl-1,3-pentadiene), and poly(4-methylstyrene)-block-polystyrene-block-poly(4-tert-butylstyrene) copolymers was also accomplished for the first time, by sequential monomer addition, in the presence of the system 1 activated by MAO. The thermal features of these polymers clearly show that all copolymer blocks, except the 4-methylstyrene one, are crystalline with melting point values typical of the corresponding homopolymers. The synthesis of a low molecular weight polystyrene sample allowed us to detect the polymer chain ends, giving useful information about the polymerization mechanism. © 2011 American Chemical Society.

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