Ring-opening polymerization of L-lactide using half-titanocene complexes of the ATiCl2Nu type: Synthesis, characterization, and thermal properties

Various half-titanocene complexes of the ATiCl2Nu type, where A is the pentamethylcyclopentadienyl (Cp*) or indenyl (Ind) group and Nu a nucleophile (ethoxy group or chloride), were used for the polymerization of L-lactide, LLA. In the cases where Nu is an ethoxy group, a 5% excess of ATiCl3 was used to accelerate the polymerization reaction. These systems were proven to be very efficient initiators for the ring-opening polymerization (ROP) of LLA in toluene at 130 degrees C. Kinetic studies revealed that in most cases the polymerization yield was quantitative and the molecular weight increased linearly with time, leading to well-defined PLLA with narrow molecular weight distributions (Mw/Mn = 1.1). LLA was also polymerized by the in situ formation of the initiating system after mixing IndTiCl3, benzyl alcohol, BzOH, and NEt3. The thermal properties of the produced polymers were examined by differential scanning calorimetry and thermogravimetric analysis. The activation energy of the thermal decomposition was calculated by the OzawaFlynnWall and Kissinger methods. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013