New Aryloxy and Benzyloxy Derivatives of Titanium as Catalysts for BulkRing-Opening Polymerization of ε-Caprolactone and δ-Valerolactone

摘要

A variety of aryloxy compounds and benzyloxy derivativesof TV' were synthesized from Ti(iPrO)4 using the alcoholysisroute. These compounds were characterized using variousanalytical methods and single-crystal X-ray diffraction. Mul-tinuclear NMR studies prove high degree of fluxional be-havior of these compounds in solution. They adopt a dimericstructure in the solid state as seen from X-ray diffractionstudies on a few of them. These compounds are powerful cat-alysts for the ring-opening polymerization of e-caprolactone(CL) and δ-valerolactone (VL) resulting in high polymerswith good number average molecular weights (Mn). Signifi-cant control can be achieved by performing such polymeriza-tions in the presence of benzyl alcohol (BnOH). This is re-flected by higher Mn and much narrower molecular weightdistributions (MWDs) of the resulting polymers. Kinetic stud-ies reveal that the rates of such polymerizations are muchhigher in the presence of BnOH. 1H NMR and MALDI-TOFstudies of low molecular weight oligomers suggest that thesepolymerizations proceed by the activated monomer mecha-nism in the presence of BnOH.