Study On The Ring-Opening Polymerization Of ?-caprolactone Catalyzed By PCL Depolymerase

Poly(?-caprolactone)is an aliphatic polyester polymerized by ring-opening polymerization of ?-caprolactone,having a wide application in packaging materials,pharmaceutical products,environmental engineering and other fields.Currently,synthetic methods of PCL are mainly chemical synthesis and biological enzymatic synthesis.Among them,the chemical synthesis method requires high reaction temperatures(150-280?),the metal catalysts are toxic and the selectivity is less.These shortcomings have limited the synthesis and production and application of PCL in certain specific areas.In contrast,biological enzymatic synthesis method using a biological enzyme catalysis,mild reaction conditions,avoiding the introduction of metal ions,as well as protection and deprotection selectively by controlling the structure of the enzyme,showing unique advantages of biocatalysis,become a hot research of polymer synthesis in recent years.In this paper,the research object were two PCL depolymerases of different properties,lipase and cutinase.The ability to catalyze reverse polyester synthesis in the non-aqueous medium of them were discussed.The process and kinetics of enzymatic ring-opening polymerization of ?-caprolactone of two enzymes were studied systematically for further study.The results are as follows:(1)Both condensation reaction between acids and diols with different lengths of chain and ring-opening polymerization of ?-caprolactone and ?-valerolactone were catalyzed by lipase DS0801 and cutinase DS1001 in the organic phase,indicating the ability of synthesizing polyester reversely of two PCL depolymerases.(2)The best result of PCLase0801 was a polymer with a uniform molecular weight distribution,the value of Mn was 6,050 g/mol,the value of Mw was 11,074 g/mol,the value of PDI was 1.7024,obtained in a reaction conducted at 100 mg enzyme powder,45?,8 h,hexane solvent,0.11 aw.The best result of PCLase1001 was a polymer with a uniform molecular weight distribution,the value of Mn was 4,326 g/mol,the value of Mw was 5,899 g/mol,the value of PDI was 1.3636,obtained in a reaction conducted at 100 mg enzyme powder,45?,8 h,solvent free,0.11 aw.(3)Characterization of the production,including 1H NMR,FT-IR,GPC,DSC,TGA and Polarized optical microscope observation,showed that the production polymerized by PCLase0801 and PCLase1001 had a value of crystallinity with 84% and 79%,and had good thermal stability,liquidity and strong penetration,and were suitable for drug delivery carrier systerm.(4)Michaelis-Menten kinetics analysis showed that,Vmax of PCLase0801 and PCLase1001 were 9.25 mg/h and 11.53 mg/h,Km of PCLase0801 and PCLase1001 were 4.21 mol/L and 2.44 mol/L,and the binding ability between enzyme and substrate was stronger than PCLase0801.(5)The adsorption rate of Amberlite XAD1180 N macroporous resin immobilized carrier for PCLase0801 and PCLase1001 was 81% and 100% respectively.Compared with the free enzyme,the immobilized enzyme improved recycling rate of enzyme with the value of 79.87%(second time)and 63.52%(third time)of PCLase0801,98.10%(second time)and 70.25%(third time)of PCLase1001 respectively.In this paper,the ability of synthesizing polyester reversely of two PCL depolymerases were studied.Combining with immobilization technology,we established the PCL synthetic route technology of enzymatic catalyzing at the laboratory level,providing a research foundation for PCL's application in the industrial production.