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.