Stereoselective Polymerization of an Aromatic Vinyl Monomer to Access Highly Syndiotactic Poly(vinyl alcohol).

ABSTRACT

Streoregular poly(vinyl alcohol) is hard to obtain because vinyl alcohol is unstable relative to its tautomer acetaldehyde, and the monomer precursor vinyl ester is poisonous to the coordination catalyst. Herein, the coordination polymerization of 2-vinyl-2,1-borazanaphthalene (BN2VN) is reported by the linked or unlinked half-sandwich ligands attached scandium precursors ((FluSiMe3 )Sc(CH2 SiMe3 )2 (THF) (THF = tetrahydrofuran, 1), (FluCH2 CH2 -NHC-R)Sc(CH2 SiMe3 )2 (THF) (R = mesityl 2, i Pr 3, Me 4), and (FluCH2 Py)Sc(CH2 SiMe3 )2 (5) for the first time. Among these precursors, complex 5 converts 600 equivalents of BN2VN into polymer within 5 min to reach an activity as high as 8.99 × 105 g molSc -1 h-1 . The resultant products show excellent syndiotacticity and melting temperatures above 300 °C, which can be transferred to syndiotactic poly(vinyl alcohol) with 90% rr triad content by postpolymerization oxidation.