Isospecific (Co)polymerization of Unmasked Polar Styrenes by Neutral Rare-Earth Metal Catalysts.

Syndioselective polymerization of unprotected polar styrenes has achieved great success via specially designed catalysts and the establishment of "self-assisted" theory. In contrast, isospecific polymerization of polar styrenes has remained less explored. Herein, we present new racemic ansa-bis(benz[e]indenyl) rare-earth metal complexes and their high activity and perfect isoselectivity (mmmm>99 %) for the polymerization of unmasked polar styrenes without any activators. Moreover, the copolymerizations of para- and meta-methoxystyrenes with styrene give gradient and random copolymers, respectively. The insertion rate of polar monomers could be readily tuned in the range of 0-100 mol % by changing their loading ratios. The resultant isotactic polar polystyrenes are quantitatively transformed into hydroxyl or methylsulfonyl polystyrenes with high T g s. DFT calculations reveal the isospecific mechanism.