Bulky titanium bis(phenolate) complexes as novel initiators for living anionic polymerization of epsilon-caprolactone

Bulky bis(phenolate) complexes of titanium alcoholates were found to initia te living polymerization of epsilon-caprolactone, affording a polyester wit h a narrow molecular weight distribution. By changing the initial monomer-t o-initiator mole ratio, the molecular weight of the polymer was controlled over a wide range. H-1 NMR studies on the produced polymer showed the prese nce of an alkoxy group originating from the initiator at the polymer termin al, indicating that the polymerization takes place at the titanium alcohola te bond of the initiator. Use of titanium complexes prepared with nonbridge d hindered phenols or a less bulky bisphenol resulted in a poorly controlle d chain growth or no polymerization.