Poly(isoprene b methyl methacrylate) block copolymer has been synthesized by rare earth coordination catalysts

which are composed of rare earth 2 ethyl hexyl phosphonates RE(P 204 ) 3

triisobutyl aluminum Al( i Bu) 3 and 1

2 dibromoethane DBE .It is found that the rare earth coordination catalysts are highly active for the block copolymerization of isoprene and methyl methacrylate.The diblock copolymer prepared has been characterized by DSC

1H NMR and 13C NMR.The block copolymer has two glass transition temperatures at -75.6℃ and 129℃ corresponding to the isoprene block phase and the methyl methacrylate block phase

respectively.The microstructure of the diblock copolymer is a highly stereoregular.For the isoprene scgment in the diblock copolymer it mainly exists in the form of cis-1

4 addition.The content of cis-1

4 addition is 97% and of 3

4-addition is 3%.For the methyl methacrylatc segment it is mostly syndiotactic

which is 74% syndiotacticity

4% isotacticity and 22% heterotacticity.The n(ad) probabilities of methyl methacrylate units in the block copolymer are calculated

and it is showed that the methyl methacrylate segment obeys second order Markov statistics model.