From Stereochemically Tunable Homopolymers to Stereomultiblock Copolymers: Lewis Base Regulates Stereochemistry in the Coordination Polymerization of 2-Vinylpyridine.

Excellent isoselectivity (mmmm > 99%) and high activity (TOF > 4000 h-1) were achieved for the first time in the polymerization of the polar 2-vinylpyridine by using the simple lutetium-based catalysts, Lu(CH2SiMe3)3(THF)x(Py)2-x (x = 0, 1, 2). The isoselectivity (mm) of the polymer could be varied between 37% and 99% through simply altering the quantity of Lewis base (tetrahydrofuran, 1,4-diazabicyclo[2.2.2]octane, 3-bromopyridine, and pyridine) added. Moreover, a novel method for preparing isotactic-atactic stereomultiblock poly(2-vinylpyridine)s was developed by the addition and removal of THF during polymerization. The polymerization process including stereoselective control mechanism was deduced by DFT calculations. [ABSTRACT FROM AUTHOR]