Four Lanthanum Schiff－base complexes were synthesized

and the polymerizations of alkyl isocyanates were studied using these complexes as single component catalysts. Lanthanum Schiffbase complexes La(HSalen1~4)3 have been synthesized by metathesis reaction of anhydrous LaCl3 with Schiffbase sodium salts NaSalen. The complex La(HSalen2)3 with the formula of ［3

5－tBu2－2－(O)C6H2CHNC6H5］3La(THF) was characterized by Xray diffraction

and the structure around Lanthanum center could be described as a pentagonal bipyramid. The polymerization of alkyl isocyanates was successfully carried out by using these complexes as single component catalysts

and the ［OC6H2CHNC6H5］3La(THF) complex (La(HSalen1)3) shows the highest catalytic activity to the polymerization of isocyanates. The influences of polymerization temperature

polymerization time

the concentration of catalyst and monomer

and the polymerization solvent on the polymerization of hexyl isocyanate (HIC) catalyzed by La(HSalen1)3 were investigated. It was found that under the polymerization conditions examined

PHIC can be prepared under -40℃~20℃ with complex La(HSalen1)3 as catalyst. Due to the depolymerization

higher reaction temperature leads to low polymer yield and molecular weight of PHIC obtained. Confirmed by GPC analysis

prolonging polymerization time is also in favor of depolymerization

the GPC profile of PHIC prepared after 12 h polymerization indicates the exist of dimmers and trimers. PHIC could be prepared with yield of 75.5%

numberaverage molecular weight (Mn) of 6.00104and MWD of 3.86 under the following optimum conditions: ［HIC］= 3.43 mol/L

［La(HSalen1)3］= 8.5810-3mol/L

polymerization at -40℃ for 12 h in toluene.