Anionic Polymerization Of Non-polarity - Polarity Triblock Copolymer Sb-mma,

In this thesis, the polymerization of triblock copolymer of styrene-butadiene-methyl methacrylate(S-B-MMA) was carried out in glass flask ,with n-BuLi as initiator, 1,1-diphenylethylene(DPE) as capping agent and Lithium 2(2-methoxyethoxy) ethoxide(LiOEEM) as additive. The copolymer was characterized by GPC, 1R, 'H-NMR, DSC and TEM; at the same time the mechanical properties of above-mentioned triblock copolymer was tested. At last, S-B-MMA used as compatibilizer and blended with PVC/SBS was also studied .The results of polymerization in the mixed solvent of toluene/THF=9/l(v/v) indicated that the living anionic polymerization of S-B-MMA was difficult to carry out because the living center of the block of PB was active, and so it was easily transferred and terminated.Homopolymerization of MMA was studied at different temperatures, with 1,1-diphenyl hexyl lithium(DPHL) as initiator, LiOEEM as additive, cyclohexane/THF=l/l(v/v) as mixed solvent. The product was identified by GPC and 'H-NMR. The results showed that in this system, the relatively low temperature(<-70℃) was required in order to avoid the side reaction and to carry out the living anionic polymerization of MMA.In cyclohexane with a small amount of THF and n-BuLi used as initiator, at 50℃, the living copolymer of SB"Li+ was prepared at first, Then it was capped with DPE, and the additive of LiOEEM with the same volume of THF as cyclohexane was added. After the temperature was cooled down to the range of -40~-78℃. then MMA was dropped slowly and polymerized. Thus, the block copolymer of S-B-MMA was synthesized. The copolymer was characterized by GPC, 'H-NMR, IR, DSC and TEM. The results showed that the copolymer was block structure and the molecular weight distribution was relatively narrow. The mechanical properties of S-B-MMA were tested. The experimental results showed that the tensile strength of S-B-MMA was equal to 7.58Mpa.The impact performance of the sample processed from the blend of S-B-MMA and PVC/SBS was tested. The results showed that the impact strength of the blending system of PVC/S-B-MMA-SBS was improved by 5~8 times than the system of PVC/SBS. The micrographs of TEM of blends and the micrographs of SEM of fractured surfaces showed that the copolymer of S-B-MMA could improve the compatibility of the blending system of PVC/SBS in effect and it also had the action of toughening agent.