Living ring-opening polymerization of cyclic carbonates mediated by bulky titanium bisphenolates

Dichlorotitanium {2,2'-methylenebis(6-tert-butyl-4-methylphenolate)} (2) brought about living homopolymerization and copolymerization of cyclic carbonates with 6- and 7-membered rings to give the corresponding polycarbonates with narrow molecular weight distribution. H-1 and C-13 NMR studies of the polycarbonates and by 2 showed the presence of terminal hydroxy groups at both polymer ends, although no signals assignable to a chlorobutyl group or bisphenolate group were observed. H-1 and C-13 NMR spectroscopy of the polymerization system showed that the cyclic carbonate molecule is coordinated to the titanium complex, whereas the structure of the titanium complex was almost unchanged throughout the polymerization. The polymerization is considered to proceed via a nucleophilic attack of hydroxy groups at the polymer ends on the cyclic carbonates activated by 2.