Bulk ring-opening copolymerization of γ-valerolactone(γ-VL)and ε-caprolactone(ε—CL)was carried out with boron trifluoride etherate complex(BF3·OEt2)as catalyst．The structures of the resultant copolemers were determined by 1H—NMR and13C-NMR spectroscopies．The molecular weight

composition and melting point of the copolymers were characterized by means of GPC

1H—NMR and DSC

respectively．Although being unable to ring—opening homopelymerize

γ-VL was ring—opening copelymerized with ε-CL to give copelymem P(γ-VL-co-ε-CL) containing certain amount of γ—VL unit．The introduction of γ—VL unit resulted in significant deerease of the molecular weight and melting point of the copolymers．The reactivity ratio of ε-CL and γ-VL was estimated as 17．6and 0．0078

respectively

by the K—T metllod．