ABSTRACT:Poly(ε-caprolactone) (PCL) having controlled molecular weight was synthesized by ring opening polymerization of ε-caprolactone (CL) initiated by ethanol with stannous(II) octanoate or scandium(III) trifluoromethane sulfonate as a catalyst. The hydroxyl end group of the resulting polymer was converted to trimethylsiloxyl group by using hexamethyldisilazane. On the other hand, poly(vinyloxy-t-butyldimethylsilane) (PVOTBDMS) was obtained by aldoltype of group transfer polymerization. Under the presence of ZnBr 2 or TiCl 4 as the catalyst, the coupling reaction of above two precursor polymers was carried out so as to build PCL-block-PVOTBDMS with controlled molecular weight and narrow molecular weight distribution. The PCL-block-PVA as the final goal could be obtained by elimination of the silyl groups in the above block copolymer.KEY WORDS Biodegradable Copolymer / Block Copolymer / Aldol-GTP / Poly(vinyloxy-tbutyldimethylsilane) / Poly(ε-caprolactone) / Living Ring-Opening Polymerization / In recent years, biodegradable polymers have attracted more and more attention from many fields to replace the traditional polymers owing to the increasing environmental problems caused by polymer disposal after use. It has been reported that they can be efficiently degraded into non-toxic water-soluble oligomers by a great number of living cells or microorganisms widely inhabited in the natural environment, then the water-soluble oligomers can be reutilized in many ways and finally changed into water, carbon dioxide or methane through several metabolic procedures of microorganisms. [1][2][3][4][5] It is well known that aliphatic polyesters are the most promising class of biodegradable materials which can be prepared by biosynthesis and chemical process 6-8 such as polycondensation and ring-opening polymerization.Poly(ε-caprolactone) (PCL) is one of the wellstudied aliphatic polyesters, which can be easily synthesized by CL with ethanol as an initiator and stannous(II) octanoate (Sn(Oct) 2 ) as a catalyst. 9-11 Up to present, Sn(Oct) 2 and aluminum triisopropoxide (Al(Oi-Pr) 3 ) have been most conventional catalysts for the ring-opening polymerization of lactones. 10, 12 Recently Kobayashi et al. insisted that rare earth metal triflates such as Sc(OTf) 3 can be used as an intriguing Lewis acid catalyst in organic synthesis. 13 Successful ring-opening polymerization (ROP) of CL using Sc(OTf) 3 was firstly reported by Nomura et al., showing the formation of PCL with very narrow molecular distribution even at 25