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

Abstract

AbstractSummary: 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. 13C 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.imageSchematic 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.