| Metallocene catalyst is a high quality olefin catalyst developed from conventional Ziegler-Natta catalyst. Compared with the conventional Ziegler-Natta catalyst, homogeneous polymerization, higher activity and narrower molecular weight distribution make it much more outstanding. However, the narrow molecular weigh distribution induces following industrial process difficult. In order to broarden the molecular weight distribution of metalloene polymer, dinuclear metallocene has been developed from the idea that two metal centers and their interaction may produce two or more catalytic centers. Many dinuclear metallocenes have been synthesized and used for olefin polymeriazation and obtained broad or bimodal molecular weight distribution polymers.In this paper, four novel dinuclear titanocenes A, B ,C ,D were synthesized and used for the bulk polymerization of methyl methacrylate(MMA) in combination with cocatalyst Al(i-Bu)3. These four catalysts can be divided into two groups based on their structure: A/Al(i-Bu)3 and B/Al(i-Bu)3 form the symmetry dinuclear titanocene group, C/Al(i-Bu)3 and D/Al(i-Bu)3 form the asymmetry dinuclear titanocene group. Each group was studied in details and obtained the following results.To the symmetry dinuclear titanocene group:Under the polymerization condition (MMA/Cat=2000, Al/Cat=20, 60℃, 15h) of A/Al(i-Bu)3 catalytic system, the conversion of MMA reached 54.80%, Mn of PMMA was 340 000 around, molecular weight distribution of PMMA was 1.68, syndiotactic content of PMMA was about 68%. Under the polymerization condition (MMA/Cat=1500, Al/Cat=10, 60℃, 15h) of B/Al(i-Bu)3 catalytic system, the conversion of MMA reached 87.21%, Mn of PMMA was about 60 000, molecular weight distribution of PMMA was 7.84, syndiotactic content of PMMA was about 76%. Compared the results of the above two catalytic systems, it is clear that A/Al(i-Bu)3 catalytic system had lower activity and obtained PMMA with higher molecular weight than B/Al(i-Bu)3 catalytic system.To the asymmetry dinuclear titanocene group:Under the same polymerization condition (MMA/Cat=2000, Al/Cat=10, 60℃, 24h) of C/Al(i-Bu)3 and D/Al(i-Bu)3 catalytic systems, the conversion of MMAreached 43.85% and 44.54% respectively, Mn of PMMA was about 125 000 and 237 000 respectively, molecular weight distribution of PMMA was 7.00 and 5.03 respectively, sydiotactic content of PMMAwas 61% and 75% respectively. Compared the results of these two catalytic systems, it is clear that these two catalytic systems have similar catalytic activity and Mn of PMMA obtained from D/Al(i-Bu)3 catalytic system higher than C/Al(i-Bu)3 catalytic system.
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