Synthesis Of Polyvinyl Alcohol With Low Degree Of Polymerization And Ultra-low Degree Of Polymerization

Polyvinyl alcohol is a widely used water-soluble polymer material,and the degree of polymerization and alcoholysis are the main factors affecting its performance.In this paper,vinyl acetate was used as raw material,azobisisobutyronitrile as initiator,methanol as solvent and carbon tetrachloride as chain transfer agent to prepare low molecular weight PVAc.After investigating the influence of initiator concentration,monomer concentration,chain transfer agent dosage,polymerization temperature and polymerization time on the degree of polymerization of polyvinyl acetate,orthogonal experimental results showed that the optimum conditions were as follows:n_{?monomer:initiator?}=25:1,V_{?monomer:solvent?}=4:3,T=65?,t=3 h,and the mass ratio of chain transfer agent to monomer is 3:100.Synthetic of PVAc with a DP of 100,PVAc alcoholysis to PVA with a molecular Weight of 5000.The polyvinyl alcohol was characterized by IR,NMR,GPC,DSC,TGA,SEM.The results show that we successfully synthesized fully and partially alcoholylated low molecular weight polyvinyl alcohols.The water solubility of PVA with different degree of polymerization and alcoholysis was investigated.It was found that the water solubility of the products with low degree of polymerization and alcoholysis was very good.The degree of alcoholysis had a great influence on the water solubility compared with the degree of polymerization.The synthesis of ultra-low degree of polymerization PVAc was investigated by using VAc as raw material,cumene hydroperoxide as initiator,methanol as solvent and dodecylmercaptan as chain transfer agent.Through optimization,the optimum conditions were as follows:n?monomer:initiator?=100:1,V?monomer:solvent?=4:3,T=90?,t=3 h,dodecyl The thiol was 0.0558 g,Poly?vinyl acetate?with the lowest polymerization degree of 100 was synthesized.By scanning electron microscopy images,we can find ultra-low molecular weight PVA morphology such as petal-like crystals;The DSC image shows that the ultralow molecular weight PVA has a crystallization temperature of33.78°C and a melting temperature of 66.40°C,which is greatly reduced compared to the market products.