Ring-opening polymerization of 2,2-dimethyltrimethylene carbonate using rare earth aryl oxides substituted by alkyl groups

Single component rare earth aryl oxides substituted by various alkyl groups [Ln(OAr)3] such as methyl,isopropyl,and tertbutyl have been developed to initiate the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate(DTC).The catalytic activity of rare earth aryl oxides,characteristics of the ring-opening polymerization as well as the polymerization kinetics and mechanism were intensively examined.The experimental results turn out that the catalytic activity of Ln(OAr)3 changes in good concordance with variation of ligands' structure and number of alkyl groups on benzene ring.The greater the ability of electron-donation of alkyl groups,the greater the catalytic activity.Moreover,the greater the number of substituted alkyls on benzene ring,the greater the catalytic activity.The results show that rare earth tris(2,4,6-tri-tert-butylphenolate)s [Ln(OTTBP)3](Catalyst 1) exhibit rather great activity in all lanthanide aryl oxides.Investigations of the polymerization mechanism by 1H NMR spectroscopy revealed that the DTC monomer inserted into the growing chains with acyloxygen bond cleavage.