Six half-sandwich rare earth catalysts Cp'LnR2(THF)n (Cp'=C5H5

C5Me4SiMe3; R=CH2C6H4NMe2-o

CH2SiMe3; Ln=Sc

Y

Lu; n=0 or 1) have been synthesized for polymerization of butadiene activated with [Ph3C]B(C6F5)4] in toluene.The polymerization activity

stereoselectivity

catalyst efficiency

molecular weight and molecular weight distribution have been studied with these catalysts.The obtained polybutadiene was characterized by 1H-NMR

13C-NMR

FTIR

GPC and DSC.The results revealed that catalyst (C5H5)Sc(CH2C6H4NMe2-o)2 shown the highest activity (up to 9600 kg-polymer/mol-Sc h)

better catalyst efficiency (45%)

high cis-1

4 selectivity (cis-1

4 content 96%) and narrow molecular weight distribution (PDI ca. 1.3).The polymerization activity was high when the polymerization was carried out in toluene or chlorobenzene and decreased with the polymerization temperature reduction.Solvents and polymerization temperature have no obviously effects on the structure of polybutadiene.When the [Bd]/[Sc] molar ratio ranged from 500 to 3000

the molecular weight of polybutadiene has increased linearly (up to 44.6104) with the constant low molecular weight distribution.The results indicated that the molecular weight and molecular weight distribution of polybutadiene could be well controlled.The glass transition temperature of polybutadiene was -107 ℃

and there are also two distinct peaks at -63 ℃ and -8 ℃ shown in DSC curves at a heating/cooling rate of 10 K/min

corresponding to the cold crystallization and melting behavior of polybutadiene.