A novel synthesis strategy combining of living ring-opening polymerization of -caprolactone and intramolecular cyclization by high efficient ring-closing metathesis reaction (RCMR) to synthesize cyclic macromolecules has been studied.First

homotelechelic PCL with hydroxyl end groups (PCLOH) was generated via living ring-opening polymerization of -caprolactone by using 2

2-dibutyl-2-stanna-1

3-dioxepane (DSDOP) as initiator.Second

homotelechelic PCLOH was reacted with vinylacetic acid

1

3-dicyclohexylcarbodiimide (DCC) and 4-(dimethylamino)pyridine (DMAP) by utilizing p-toluenesulfonic acid monohydrate (PTSA) as catalyst and then converted to homotelechelic PCL with allyl end groups (allylPCL).Finally

cyclic ploy(caprolactone) was synthesized by ring-closing metathesis reaction of allylPCL by using bis(tricyclohexylphosphine) benzylidine ruthenium (IV) dichloride(Cl2(Cy3)2Ru CHPh)as catalyst under high dilution.The structures and thermodynamic properties of polymers were characterized by SEC

NMR

TGA and DSC technologies.The characterization by SEC and viscosity showed that the hydrodynamic volume of cyclic poly(-caprolactone) was smaller than that of its linear precursor.DSC study showed that the Tm and Hm of cyclic poly(-caprolactone) was lower than those of its linear precursor.TGA test showed that the Tmax of cyclic poly(-caprolactone) was 13 K higher than that of its linear precursor.The results indicated that the intra-molecular cyclization of homotelechelic allylPCL by RCMR was high efficient under the high dilution (2.510-5 mol/L) because the resulted cyclic PCL was pure and no need for further purification.