Polymer Bulletin, Vol.75, No.11, 5179-5195, 2018
Kinetics, mechanisms and polymer property studies of ring-opening polymerization of -caprolactone and lactides initiated by (benzimidazolylmethyl)amino Zn(II) alkoxides
The reactions of substituted (benzimidazolylmethyl)amines ligands (L1-L3) with ZnEt2 in the presence of either BnOH or t-BuOH afforded the corresponding Zn(II) metal alkoxides [Zn(L1)(OBn)](2) (1), [(Zn(L2)(OBn)](2)(2), [Zn(L3)(OBn)](2) (3), [Zn(L2)(t-BuO)](2) (4), respectively. Complexes 1-4 formed effective initiators in the ring-opening polymerization (ROP) reactions of -caprolactone (-CL), (D,L)-lactide ((D,L)-LA) and (L)-lactide ((L)-LA). The ROP reactions followed pseudo-first-order kinetics with respect to monomer. Moderate molecular weight polymers of 10,650gmol(-1) exhibiting relatively narrow molecular weight distributions (1.16-1.54) were obtained. Predominantly crystalline isotactic poly((L)-LA) and heterotactic poly((D,L)-LA) were produced, respectively. Thermal analyses of PLA also supported the formation of isotactic poly((L)-LA) with decomposition temperature of 298 degrees C.