乙烯与1-己烯共聚及其共聚物的微观结构

采用限制几何构型催化剂2-四甲基环戊二烯基-4,6-二叔丁基苯氧基二氯化钛/助剂Al(i-Bu)3-Ph3C]+B(C6F5)4]-催化体系催化乙烯与1-己烯共聚,采用13 C NMR、GPC和DSC表征了共聚物的结构和性质,探讨了反应温度(40~80℃)和共聚单体初始浓度(0.1~0.4mol/L)对该体系催化活性和共聚物性质及其微观结构的影响,并采用一级Markovian模型和Bernoullion模型对共聚物序列分布进行概率统计分析。结果表明,在实验条件下,得到的共聚物是无规结构的聚合物,具有较低的相对分子质量((0.87~6.73)×104)、适中的共聚单体质量分数(8.8%~28.8%)和熔点(107.5~121.0℃)。该共聚物的链增长符合一级Markovian模型的链增长机理,1-己烯共聚单体配位或插入到{共聚物链-1-己烯-1-己烯-催化剂}序列(HH])要比配位或插入到{共聚物链-乙烯-1-己烯-催化剂}序列(EH])更容易(概率参数PHHPEH),乙烯共聚单体配位或插入到{共聚物链-乙烯-乙烯-催化剂}序列(EE])要比配位或插入到{共聚物链-1-己烯-乙烯-催化剂}序列(HE])更容易(概率参数PEEPHE)。PEH0.5和PHE0.5表现出了随机分布的乙烯基共聚物的特征。

Copolymerization of Ethylene and 1-Hexene and Microstructure of the Copolymers

Copolymerization of ethylene and 1-hexene was performed by using a constrained geometry catalyst of 2-(tetramethyl cyclopentadienyl)-4,6-di-tert-butylphenoxy-titanium dichloride with Al(i-Bu)3-Ph3C]+B(C6F5)4]-. The copolymers were characterized by 13C NMR, DSC and GPC methods. The effects of reaction temperature (40-80℃) and the concentration of 1-hexene comonomer（0.1-0.4mol/L）on the copolymerization activity and properties of the copolymers were investigated. The probability analysis of the monomer triad sequence distribution was carried out based on the first-order Markovian model and Bernoullion model. The effect of the concentration of 1-hexene and reaction temperature on monomer sequence distribution was discussed. The results showed that the copolymers possessed a atactic structure, with the relative molecular mass of (0.87-6.73)×104, the co-monomer content of 8.8%~28.8% and the melting point of 107.5-121.0℃. The propagation mechanism of the copolymerization process was corresponded to the first-order Markovian model. It is more probable that a 1-hexene monomer unit is added to the sequence {polymer-1-hexene-1-hexene-catalyst} than to the sequence {polymer-ethylene-1-hexene-catalyst} (PHH>PEH), meanwhile, anethylene monomer unit is added to the sequence {polymer-ethylene-ethylene-catalyst} more easily than to the sequence {polymer-1-hexene-ethylene -catalyst} (PEE> PHE).The value of probability parameters (PEH0.5) showed a feature of vinyl copolymer possessing a random distribution.