Single Electron Transfer Living Free Radical Polymerizations Of Vinyl Chloride And Butyl Acrylate

The glass transition temperature of poly(vinyl chloride) (PVC) can be reduced, and the flexibility of PVC can be improved by copolymerizing of soft monomer or flexible polymer with vinyl chloride (VC). In all kind of copolymerization methods, synthesizing of internal plasticized PVC block copolymer is the most difficult due to the difficulty and lower controllability of VC living radical polymerization. In this thesis, based on a goal of synthesizing internal plasticized PVC block copolymer, the living polymerizations of VC and butyl acrylate (BA) by single electron transfer(SET) mechanism were carried out, and influences of polymerization method, the concentrations of catalyst and initiator, polymerization on the polymerization kinetics were investigated.Firstly, SET suspension living radical polymerizations of VC were conducted by using CHI3 as the initiator, and Na2S2O4 as the catalyst. Through polymerizations in sealed tube, it was found that that the primary radicals decomposed from CHI3 and Na2S2O4 had a great effect to polymerization rate. CHI3 with high purity should be used in polymerization. Then, VC SET-LRPs were scaled-up in a 5L reactor and the kinetics was studied. SET-LRP of VC could proceed under a mild condition, but the polymerization rate was low. By measuring the conversion of VC, mean molecular weights and molecular weight distribution (MWD) of PVC, it was found that there were two kinds of polymer with different molecular weights formed during polymerization process. The weight fraction of PVC with high molecular weight was almost linearly increased as the conversion increased. In a certain conversion range, the as-prepared PVC has a polydispersity index (PDI) within 1.5. The resulted PVC had chlorine methyl iodide active chain end structure, indicating the living nature of VC polymerization.It is considered that the heterogeneous characteristics of VC suspension polymerization influenced the diffusion and activity of free radicals and monomer, leading the lower controllability of polymerization and the formation of PVC with relatively wider distribution. SET suspension living radical polymerizations of BA exhibited a much great polymerization rate than VC at the same concentrations of CHI3 and Na2S2O4. In suspension polymerization, PBA was easy to form the flocculation and coagulation. The emulsion polymerization was not very stable and prepared PBA had a wider molecular weight distribution.It is considered that the monomer droplets and polymer particles formed in BA suspension polymerization were bigger, which was not favor to the diffusion of free radicals. CHI3 had a distribution in monomer droplets and latex particles in emulsion polymerization of BA, the diffusion of the free radicals was complicated, leading the lower controllability of polymerization.The SET miniemulsion polymerization of BA were carried out using CHI3 as the initiator, Na2S2O4 as the catalyst, and sodium dodecyl sulfate (SDS)/hexadecane as emulsifier/co-emulsifier. It was found that SET miniemulsion polymerization of BA exhibited greater reaction rates and better controllability, and the usage of catalyst and initiator was lower. Furthermore, the results show that the miniemulsion polymerization of BA was better to conducted near 30?.The initiator content should not be greaterr than [CHI3]/[BA]=1/400. As the concentrations of emulsifier and co-emulsifier increased, the stability of polymerization system could be improved and the reaction could be speeded up. Continuously adding the catalyst in the polymerization would maintain the catalytic activity for a long time and increase the controllability on the reaction.The prepared PVC and PBA were used as macro-initiator to re-initiate the further SET of VC and/or BA. It was found that PVC and PBA exhibited livingness and re-initiation the copolymerization to obtain PVC block copolymers. Specially, using the miniemulsion polymerization of VC initiated by PBA prepared by miniemulsion polymerization, the stable PBA-b-PVC copolymer emulsion could be prepared, and homogeneous soft PVC block copolymers could be obtained finally.