New Aryloxy and Benzyloxy Derivatives of Titanium as Catalysts for Bulk Ring‐Opening Polymerization of ϵ‐Caprolactone and δ‐Valerolactone

Abstract

AbstractA variety of aryloxy compounds and benzyloxy derivatives of TiIV were synthesized from Ti(iPrO)4 using the alcoholysis route. These compounds were characterized using various analytical methods and single‐crystal X‐ray diffraction. Multinuclear NMR studies prove high degree of fluxional behavior of these compounds in solution. They adopt a dimeric structure in the solid state as seen from X‐ray diffraction studies on a few of them. These compounds are powerful catalysts for the ring‐opening polymerization of ϵ‐caprolactone (CL) and δ‐valerolactone (VL) resulting in high polymers with good number average molecular weights (Mn). Significant control can be achieved by performing such polymerizations in the presence of benzyl alcohol (BnOH). This is reflected by higher Mn and much narrower molecular weight distributions (MWDs) of the resulting polymers. Kinetic studies reveal that the rates of such polymerizations are much higher in the presence of BnOH. 1H NMR and MALDI‐TOF studies of low molecular weight oligomers suggest that these polymerizations proceed by the activated monomer mechanism in the presence of BnOH. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)