Experimental Study On The Preparation Of Poly(?-Caprolactone)from Cyclohexanone Catalyzed By Lipase

Poly(?-caprolactone)(PCL)is a highly biodegradable material with excellent biocompatibility,material compatibility and solvent solubility,and has important application value in biomedicine,agriculture,chemical and other fields.The synthesis of polycaprolactone mostly uses caprolactone as a monomer for polymerization,and the raw material cost is high.Traditional chemical synthesis methods can obtain high molecular weight polycaprolactone,but there are heavy metal residues and toxicity problems.The existing enzyme-catalyzed method has mild reaction conditions,but also has problems such as large amount of enzyme and low catalytic efficiency.Therefore,the research on the efficient synthesis process of polycaprolactone has important practical significance.This study directly synthesized poly?-caprolactone by lipase-mediated potting with cyclohexanone as a raw material,greatly simplified the process step.In this thesis,the research on the reaction conditions of lipase-mediated one-pot synthesis of polycaprolactone was carried out,and the reaction conditions were optimized.The influence of factors such as reaction temperature,molar ratio of substrate,type of acyl donor,reaction time and other factors on the yield and molecular weight of PCL were mainly investigated.The response surface method(RSM)was used to optimize the key parameters of lipase-mediated one-pot synthesis of PCL.The optimized conditions were as follows:the lipase addition amount was 28.5 mg/m L system,the reaction temperature was 60?,the molar ratio of urea hydrogen peroxide(UHP):cyclohexanone is 1.32:1,under these optimal conditions,the PCL yield was96.5%and the molecular weight(Mn)was 3312.The optimal mathematical model based on RSM was established,and the quadratic polynomial regression equation was obtained.The analysis of variance showed that the addition of lipase had the most significant effect on the yield of poly?-caprolactone.The R~2 value of the model was 0.9997,indicating that the model can better predict the experimental results.In addition,a preliminary analysis of the reaction mechanism was carried out.According to the experimental results,it is concluded that there is a fourth reaction in the reaction system,that is,the immobilized lipase catalyzes the reaction of acetic acid with UHP to form in-situ peracetic acid.It not only reduces the amount of urea hydrogen peroxide used in the reaction,but also recycles the generated acetic acid,thereby reducing its damage to enzymes and improving the economic benefits of the reaction.The above research results show that the lipase-mediated one-pot polycaprolactone synthesis process is expected to become an effective alternative to the traditional process and has a good application prospect.