Isolated Ethylene Units in Isotactic Polystyrene Chain: Stereocontrol of an Isospecific Post‐Metallocene Titanium Catalyst

Summary: Copolymerization of styrene with small amounts of ethylene using the catalyst system dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐ tert ‐butyl‐phenoxy)}titanium/methylaluminoxane results in the unprecedented formation of isotactic polystyrene containing isolated ethylene units. 13 C NMR spectroscopic analysis of the copolymer indicates that an “enantiomorphic site” control mechanism for isospecific propagation is operating. DSC measurements also indicate the presence of isolated ethylene units which modify the crystallization behavior of the isotactic polystyrene. Schematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system. image Schematic representation of the copolymerization of styrene with small amounts of ethylene using dichloro{1,4‐dithiabutanediyl‐2,2′‐bis(4,6‐di‐tert‐butyl‐phenoxy)}titanium/methylaluminoxane as catalyst system.