单茂钪催化对氟苯乙烯间规聚合及与乙烯共聚合的研究

Syndiotactic Homo-and Co-polymerization of p-Fluorostyrene and Ethylene Catalyzed by Half-sandwich Scandium Complexes

采用(C5Me4Si Me3)Sc(CH2C6H4NMe2-o)2(1)和(C5Me4Si Me3)Sc(CH2Si Me3)2(THF)(2)2种单茂钪催化剂,考察了其催化对氟苯乙烯均聚合以及与乙烯共聚合的性能,并通过1H-NMR、13C-NMR、GPC和DSC对所获聚合物的微观结构和热性能进行了分析.结果表明,单茂钪1可以催化对氟苯乙烯均聚合,获得间规聚合物,但聚合活性较低.采用单茂钪2,控制溶剂种类和用量可以获得间规和无规2类聚合物:控制对氟苯乙烯单体在氯苯溶剂中浓度低于2.4 mol/L,可获得间规聚对氟苯乙烯(rrrr≥99%,Tm≥319oC),且聚合活性高达105 g polymer molSc-1 h-1;控制对氟苯乙烯单体在氯苯溶剂中浓度高于4.8 mol/L或者选用氟苯做溶剂,可获得无规聚对氟苯乙烯;固定单体浓度调控对氟苯乙烯和催化剂的比例,可获得分子量(Mn)在3.10×104~2.08×105间调控的间规和无规聚对氟苯乙烯.在常压乙烯下,单茂钪1和2还可以催化对氟苯乙烯与乙烯共聚合,获得了组成(对氟苯乙烯含量41 mol%~88 mol%)和分子量(3.10?104~1.84?105)可控的两元共聚物,共聚合活性高达106 g polymer molSc-1 h-1.当共聚物中乙烯含量高于对氟苯乙烯含量时,共聚物仅有源自聚乙烯嵌段的熔点(119~126oC).当共聚物中对氟苯乙烯含量高于乙烯含量时,共聚物出现聚对氟苯乙烯嵌段;由单茂钪1获得聚对氟苯乙烯嵌段为间规结构,共聚物具有熔点(269~282oC)和玻璃化转变温度(Tg,79~82oC);单茂钪2获得聚氟苯乙烯嵌段为无规结构,共聚物仅有1个Tg(94~96oC).

Syndiotactic polymerization ofp-fluorostyrene and its copolymerization with ethylene catalyzed by half-sandwich scandium complex （CsMe4SiMe3）Sc（CH2C6H4NMe2-o）2 （1） and （CsMe4SiMe3）Sc（CH2Si- Me3）2（THF） （2） have been examined. The microstrucmres and thermal properties of the obtained polymers were characterized by 1H-NMR, 13C-NMR, GPC and DSC. Scandium complex 1 showed syndiotactic selectivity for the polymerization ofp-fluorostyrene with low activity （103 g polymer moist-1 h-l）. Scandium complex 2 proved to be a high activity catalyst for the polymerization of p-fluorostyrene to afford syndiotactic or atactic poly（p-fluorostyrene） by controlling the type and the volume of the solvent. When the concentration of p-fluorostyrene in chlorobenzene was below 2.4 mol/L, the syndiotactic poly（p-fluorostyrene） （rrrr 〉 99%） was obtained with scandium complex 2 possessing high activity （105 g polymer moist-1 h-l）. The melting point （Tm） of syndiotactic poly（p-fluorostyrene） reached up to 324 ℃, suggesting the semicrystalline morphology of this polymer. The molecular weight of the syndiotactic poly（p-fluorostyrene） （Mn = 3.10 × 10^4 - 2.08 × 10^5） was easily controlled by changing the feed ratio ofp-fluorostyrene to catalyst. When the concentration ofp-fluorostyrene in chlorobenzene was above 4.8 mol/L or fluorobenzene used as solvent, atactic poly（p-fluorostyrene） with controllable molecular weight （3.80 × 10^4 - 1.88 × 10^5） was obtained. Moreover, the copolymerizations of p-fluorostyrene with ethylene catalyzed by complexes 1 or 2 have also been prepared, leading to novel copolymers with controlled composition （p-fluorostyrene content： 41 mol% - 88 mol%） and molecular weight （3.10 x 104 - 1.84 x 105）, and with high activity （up to 106 g polymer moist-1 h-l）. When ethylene content in the copolymer is higher than that ofp-fluorostyrene, the copolymers showed a Tm around 119 - 126 ℃ owing to polyethylene blocks. When p-fluorostyrene content in the copolymer is higher than that of ethylene, the obtained copolymers with syndiotactic poly（p-fluorostyrene） blocks, prepared by scandium complex 1, showed a Tm around 269 - 282 ℃ and a Tg around 79 - 82 ℃; In contrast, the copolymers with atactic poly（p-fluorostyrene） blocks prepared by scandium complex 2 showed their Tg around 94 - 96 ℃.