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The cationic polymerization of 1,3-pentadiene using a tert -butyl chloride ( t BuCl)/TiCl 4 initiating system in CH 2 Cl 2 at different reaction conditions is reported. It is shown that the reaction rate increases with the increase of the t BuCl/TiCl 4 molar ratio, while the molecular weight distribution becomes narrower. Well-defi ned oligo(1,3-pentadiene)s (M n ≤ 3500 g mol − 1 ; M w /M n ≤ 3.0) are obtained at high t BuCl/TiCl 4 molar ratio (340) and low temperature (-78 °C). 1 H and 13 C NMR spectroscopy studies reveal the presence of tert -butyl head and -CH 2 -Cl end groups. The number-average functionalities ( F n s) at the α -and ω -ends are calculated to be F n ( t Bu) > 1 and F n (Cl) < 1, respectively. The general mechanism of 1,3-pentadiene polymerization is proposed.

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