Study On A New Preparation Method Of Epoxidized Natural Rubber Grafted Copolymer

At present, graft modification of natrual rubber is mainly through radical polymerization. Because of this method is always out of control of the reaction of the chain termination and transfer, it's hard to control the molecular weight of graft chains accurately, the graft density is also undeterminable. Applying atom transfer radical polymerization (ATRP) to graft copolymerization, the molecular weight of graft chains will be controllabled. And because the graft copolymrization only take place on initiation point, the graft copolymer has a clear structure.There are two ways to graft polymer chain noto NR, one is to insert the chain in the a-H position of NR molecule chain, the other in the double-bond position. In this thesis, the second way was taken, using two-step method to prepare macroinitiator and then to initiate ATRP. First of all, NR was partially epoxidized to prepare epoxidized natural rubber (ENR), the epoxy introduced being capable to react with bromo-carboxylic acid to prepare macroinitiator, bromo-functionalized ENR (ENR-Br), in which the graft site locates in the double-bond position. And then ENR-Br was used to initiate polymerization of methyl methacrylate (MMA) and styrene (St), two new kinds of ENR grafting materials, ie ENR-g-PMMA and ENR-g-PS, being obtained.In the section of preparing macroinitiator, the reaction conditions and the structures of products of ENR ring-opening reacting with2-bromo-2-methylpropionic acid was studied. Results show that during the ring-opening reaction side reactions as ring-rearrangement into allyl alcohol and cyclization to form five-membered ring structure occurred. Studies on the effect of reaction conditions such as acid dosage, temperature and reaction time indicate that the side reactions can be aggravated when the acid dosage and the temperature is too high and reaction time too long. Ring-opening byproducts should be controlled by selecting reaction conditions appropriately to reduce the amount of by-products and improve the content of the component being active to initiate ATRP.In the section of ATRP grafting, ENR-g-PMMA and ENR-g-PS were prepared using ENR-Br as initiator, CuBr/PMDTA as catalyst, toluene as solvent. The structure of reaction product was researched by IR and1H NMR. An effect of polymerization conditions on grafting was studied too. The linearity of plot of ln([M]0/[M]t) versus time was observed in the system, which indicates of first-order kinetic reaction. PS grafts was cleaved from NR backbone by hydrolysis and GPC was used to analyze the molecular weight (Mn,GPC) and polydispersity indexe of the grafts, results show that Mn,GPC increases with monomer conversion. This thesis provided a new way to prepare NR grafting copolymer, and also a research basis to high properties of NR graft copolymer with well-defined structure.