DFT study of lactide ring-opening polymerizations by aluminium trialkoxides: Understanding the effects of monomer, alkoxide substituent, solvent and metal

摘要

The initiation of the ring-opening polymerization (ROP) of l-lactide, d-lactide and meso-lactide (namely, LLA, DLA and mLA, respectively) initiated by aluminium trialkoxide complex with formulae Al(OR)(3)(R = Me, Pr-i and Bu-s) are investigated using DFT calculations. The results show that all Al(OR)(3)/lactide systems initiate through a coordination-insertion mechanism, involving the rate-limiting "pendulum" transition state. The reactivities of the lactides are predicted to increase as mLA < DLA < LLA. The rate for the LA ROP initiation was slightly slower in polar solvents. Metal substitutions show a reactivity trend (Al < Sc < Y) with different reaction steps.