乙烯-降冰片烯共聚物的合成

Synthesis of ethylene-norbornene copolymers

采用不同的工艺合成了一系列乙烯-降冰片稀(NBE)共聚物,利用高温凝胶渗透色谱仪、差示扫描量热仪和核磁共振波谱仪表征了共聚物。相对优化的合成条件为:催化剂A,聚合温度25℃,NBE浓度为0.9 mol/L。乙烯-NBE共聚物的链结构主要以EENEE(E代表乙烯,N代表NBE)形式存在,少数以ENENENE形式存在。共聚物的相对分子质量随聚合温度的升高而明显减小,且低聚物含量增加较多;用催化剂A合成的产物中含有质量分数为0.4%的低聚物,适量的低聚物起到润滑作用,有利于产品的后加工;在低NBE浓度范围,随NBE浓度增加,合成的共聚物重均分子量降低且相对分子质量分布变窄。

A series of ethylene-norbornene （NBE） copolymers were synthesized with different process conditions and then, were characterized by high temperature gel permeation chromatography （HTGPC）, differential scanning calorimetry （DSC） and nuclear magnetic resonance spectroscopy （NMR）. The comparatively optimized synthetic conditions mainly included polymerization temperature of 25 ~C, NBE concentration of 0.9 mol/L and usage of catalyst A. The chain structure of the ethylene-NBE copolymers mostly existed in the form of EENEE, and only small part of it assumed the form of ENENENE. A significant reduction in relative molecular mass of the copolymers and an obvious increase in content of oligomers appeared as the polymerization temperature rose. In the polymers synthesized in the presence of catalyst A the oligomer content accounted for 0.4%. The oligomers in proper amounts could act like lubricant and favor the processing of the ethylene-NBE products. Gradually increasing NBE concentration could decrease weight average molecular mass and narrow the relative molecular mass distribution of the copolymer as long as the NBE kept in the low concentration range.