writer：Zhen Zhanga , Yang Jiang , Kai Zhang , Zhong-Yi Cai* , Shi-Hui Li *, and Dong-Mei Cui
keywords：DMAO; Syndiotactic polystyrene; Styrene; Ethylene; Copolymerization
source：期刊
specific source：Chinese J. Polym. Sci. 2021, 39, 1185–1190
Issue time：2021年

The catalytic performance of rare-earth metal dialkyl complexes in combination with DMAO (dry methylaluminoxane) is explored. In the presence of 60 equivalents of DMAO, the half-sandwich complex (C₁₃H₈CH₂Ph)Sc(CH₂SiMe₃)₂(THF) (1) is inert for styrene polymerization, but (C₅Me₄Ph)Sc(CH₂C₆H₄NMe₂-o)₂ (2) converts 18% styrene into syndiotactic polystyrene. Under the same conditions, the constrained-geometry configuration sandium complex (C₁₃H₈CH₂Py)Sc(CH₂SiMe₃)₂ (3a) displays extremely high catalytic activity (>6420 kg·molSc ^?1·h^?1 ) and perfect syndiospecific (rrrr>99%) for styrene polymerization, while its lutetium (3b) and yttrium (3c) analogues are nearly inactive. Although the binary catalytic system 3a/DMAO exhibits very low activity for 4-methoxystyrene polymerization, it is an efficient catalyst for the syndioselective polymerization of other styrene derivatives such as 2-methoxystyrene, 4-methylthiostyrene, 4-fluorostyrene, 4-dimethylhydrosilylstyrene, alkyne- susbstituted styrenes and 4-methylstyrene. In addition, the binary system 3a/DMAO can copolymerize ethylene and styrene to give alternating copolymers with a single glass transition at 80 °C and 0.4 MPa ethylene pressures. By increasing styrene feed amount from 20 mmol to 60 mmol, the styrene content slight increases from 48.2 mol% to 53.8 mol%, but the polymerization activity is obviously promoted from 240 kg·molSc ^–1·h^–1to 532 kg·molSc ^–1·h^–1.