Process For Controlling Peptization Of Sulfur Modified Polychloroprene Latex And Synthesis Of Graft Copolymer By Controlled/Living Radical Polymerization

The research on the controlled peptization of sulfur modifided polychloroprenelatex,and the synthesis ofpolychloroprene-gra/-polystyrene and polychloroprene-gra/r-ploy (methyl methacrylate) by atom tansfer radical polymerization was carried out in this dissertation.The peptization is meant to breakdown or partial breakdown of sulfur link in polychloroprene to give more plastic product. However, peptization would go on when Mooney viscosity was desired in the presence of peptizors. The first part of research is a process for retarding peptization of sulfur modified polychloroprene with TETD/SDC or TETD by the addition of oxidation agent, such as potassium persulfate. Potassium persulfate added into the sulfur modified polychloroprene latex with TETD/SDC system was successful to retard the peptization process. The temperature between 30 to 50 had little effect on potassium persulfate retarding system in the presence of TETD/SDC. Potassiumpersulfate was also added into the sulfur modified polychloroprene latex from workshop with TETD system. The same results were obtained. Like potassium persulfate, ammonia persulfate, hydrogen peroxide and their mixture could aalso retard the peptization process.Because polychloroprene contains allyl chloride groups as structural defects, it was used as macroinitiator for grafting copolymerization of styrene and methyl methacrylate by atom transfer radical polymerization with toluene or cyclohexatone as the solvent. The polymerization of styrene and methyl methacrylate initiated by allyl chloride as model initiators were investigated. The atom transfer radical polymerization of styrene showed controlled polymerization. When methyl methacrylate was used, the polymerization was uncontrolled which was similar to the conventional free radical polymerization due to the observed initial rate lower than the propagation rate of methyl methacrylate. Polychloroprene as macroinitiators initiated the copolymerization of styrene and methyl methacrylate. The resulting copolymers were characterized by GPC and !H NMR. However, the degradation of polychloroprene during the synthesis results in the decreases of number average molecular weights of copolymers.