The sodium amides of telechelic polytetranydrofuran with secondary amine as endgroup (PTHF-NHR，where R represents benzyl

n-butyl or phenyl group)synthesized by termina-ring the dicationicaUy living polymerization of tetrahydrofuran (THF) with a large excess of primary amine were used as polymeric catalysts for anionic block copolymerization of vinyl monomers (methyl methacrylate，styrene or acrylonitrile)．When R is a phenyl group，the PTHF-NHR can be almost completely metallated by sodium naphthalene．On the poly-meric anion from the subsequendy formed sodium amide a quantitative polymerization of MMA leads to the formation of a block copolymer，poly(MMA-b-THF-b-MMA)，which ex- hibits the general properties of thermoplastic ehstomer with a tensile strength of 157 kg／cm2 and dongation of 700%．