Ring-opening Polymerization And Copolymerization Of ?-pentadecalactone And ?-caprolactone Catalyzed By Organocatalytic With MgI₂

In this paper,the cooperative interaction of 2,3,6,7-tetrahydro-5H-thiazolo [3,2-a]pyrimidine?ITU?with MgI₂ as Lewis acidic cocatalyst was employed for the homo-and copolymerization of ?-pentadecalactone?PDL?and ?-caprolactone?CL?.In order to assess the catalytic activity of ITU/MgI₂,the effects of reaction conditions,including reaction time and temperature,the molar ratio of ITU to MgI₂,the molar ratio of monomer to catalyst,the molar ratio of monomer to initiator,and the concentration of monomer on polymerizations were discussed systematically.And the kenitic of ring-opening polymerization of PDL catalyzed by ITU/MgI₂/BnOH system was studied in detail.The structure of the polymers was characterized by GPC,DSC,IR,1H NMR and 13 C NMR.And the possible polymerization mechanism was speculated.In the presence of benzyl alcohol,ring-opening homopolymerization of PDL catalyzed by ITU/MgI₂ cocatalyst has been carried out.By varying the experimental conditions,a high molecular weight?Mn = 66.7 kg/mol?and relatively narrow molecular weight distribution polymer?PDI = 1.31?was obtained.The optimum conditions can be described as: [ITU]:[MgI₂] = 1:1?molar ratio?,[M]/[ITU] = 200?molar ratio?,[M]/[I] = 100?molar ratio?,[M] = 1.0 mol/L,70 ?,12 h,in toluene.The kinetic studies indicated that the polymerization rate was first-order with respect to monomer and catalyst concentration,which can be written as: Rp = Kp[PDL][ITU].According to the Arrhenius equation,the apparent activation energy of the polymerization was 40.95 KJ/mol.The DSC curve of the PPDL showed a melting point of 93.0 ? and a crystallization temperature of 73.7 ?.Results of IR and 1H NMR indicated that the homopolymer of PDL catalyzed by ITU/MgI₂/BnOH was prepared successfully.And we speculated the possible mechanism.We also utilized ITU/MgI₂ as the cocatalyst and BnOH as the initiator to synthesize the P?PDL-co-CL?in toluene.Effects of different reaction conditions on the copolymerization have been examined systematically and the optimum conditions of the ring-opening copolymerization of PDL with CL can be described as: [ITU]:[MgI₂] = 1:1,[PDL]/[CL] = 1:1in feed,[PDL+CL]/[ITU] = 100,[PDL+CL] = 2.0 mol/L,[PDL+CL]/[I] = 100.The copolymerization proceeded under appropriate conditions?70 ?,in toluene,12 h?affording copolymer with Mn value up to 56.8 kg/mol?99.6 %?and rather moderate dispersity value?PDI = 1.33?.Thermal transition temperatures measured by DSC further supported the random nature of these copolymers.The copolymers were all shown to cocrystallize to produce polymers with melting and crystallization temperatues that displayed a linear relationship with respect to the molar ratio of PDL and CL.The random structure of the copolymers can be confirmed by IR,1H NMR and 13 C NMR analyses that P?PDL-co-CL?is a nearly ideal random copolymer.