新型限制几何构型稀土金属有机配合物催化苯乙烯与乙烯共聚合

摘要

合成了2种限制几何构型稀土配合物(IndCH2-Py)2Sc(CH2 SiMe3)(1)、(FluCH2-Py)Sc(CH2 SiMe3)2(2) (Py=Pyridyl；Ind=Indenyl；Flu=Fluorenyl),在有机硼盐与烷基铝的活化下,表现出了不同的催化行为；配合物2组成的催化体系可以引发苯乙烯与乙烯共聚,得到多嵌段共聚物,共聚活性最高达1.21×103 kg/(mol(Sc) ·h).该共聚物经化学溶解性实验和凝胶渗透色谱表征,证明无均聚物存在.共聚物中,聚苯乙烯链段保持间规性,并且其含量可调.由示差扫描量热法得到了不同投料比所得共聚物的熔点(237 ～ 257℃).共聚物的相对分子质量为3.2 ×104 ～10.7 ×104,相对分子质量分布为2.05 ～2.34.%Novel constrained-geometry-configuration ( GGC ) rare-earth metal complexes(IndCH2-Py)2Sc(CH2SiMe3)(l) and (FluCH2-Py) Sc ( CH2 SiMe3 ) 2 (2) (Py = Pyridyl,Ind = Indenyl,Flu = Fluorenyl) have been synthesized by treating rare-earth metal trisalkyls with CpCH2-Py(Cp = Ind,Flu) compound,and fully characterized by NMR and X-ray diffraction analyses.Upon activation with AliBu3 and [Ph3C] [B ( C6F5 )4 ] ,the two compounds showed different catalytic behavior towards copolymerization.A catalytic system containing complex 2 could initiate the copolymerization between styrene and ethylene while complex 1 was inert for the same purpose.Both geLpermeation chromatography ( GPC ) curves and solvent extraction experiments corroborated that the products were mainly consisted of copolymers with negligible by product.The catalytic system based on complex 2,not only exhibited excellent activity ( up to 1.21× 103 kg/(mol(Sc)·h) and selectivity for syndiospecific styrene polymerization and styrene-ethylene copolymerization,but also afforded syndiotactic styrene-styrene sequences with controllable styrene contents in the styrene-ethylene copolymers.These copolymers were further confirmed by the observation of an endothermic peak (Tm) at 237～253℃ in the differential scanning calorimetry ( DSC) curves.These copolymers have moderate relative molecular niass(Mn =3.2×104～10.7×104 ) and relative molecular mass distributions (Mw/Mn =2.05～2.34).