乙丙共聚型聚合物的制备与结构表征

Preparation and Structure Characterization of Ethylene-Propylene Rubber-type Polymers

后过渡金属催化剂以其独特的“链行走和链伸直”机理在催化α-烯烃聚合时可得到结构独特与性能优异的聚烯烃弹性体。本文以经典的α-二亚胺镍(Ⅱ)配合物(C1~C6)为催化剂,在倍半乙基氯化铝(EASC)作用下,催化丙烯聚合,制得了结构为乙丙共聚型聚合物(EPR-型聚合物)。系统考察了催化剂用量、n(Al)/n(Ni)、丙烯压力、聚合时间、聚合温度、溶剂和催化剂结构对丙烯聚合的影响,得到了最优化的聚合条件。通过核磁共振波谱(NMR)、红外光谱(IR)、凝胶渗透色谱(GPC)、差示扫描量热(DSC)和热重分析(TGA)对所得聚合物的微观结构、热性能进行了分析与表征。结果表明,α-二亚胺镍(Ⅱ)配合物的催化活性最高可达6.33×10^(5)g/(mol·h),所得聚合物的分子量范围为6.27×10^(4)~40.75×10^(4)g/mol,1,3-成键率为21%~35%(mol),玻璃化温度为–28.95~–40.57℃,分解温度在400℃以上。

Late-transition metal catalysts can be applied in the polymerization ofα-olefins with a unique“chain-running and chain-straightening”mechanism to produce polyolefin elastomers with special structures and excellent properties.In this study,ethylene-propylene rubber(EPR)-type polymers were prepared by polymerization of propylene with classicalα-diimine nickel(II)complexes(C1~C6)in the presence of ethylaluminum sesquichloride(EASC).The effects of catalyst dosage,n(Al)/n(Ni),propylene pressure,polymerization time,polymerization temperature,solvent,and structures of the catalysts on the polymerization were investigated systematically,and the optimal polymerization conditions were obtained.The microstructures and thermal properties of the obtained polymers were characterized by using nuclear magnetic resonance spectroscopy(NMR),infrared spectrum(IR),gel permeation chromatography(GPC),differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA).The highest catalytic activity ofα-diimine nickel(II)complexes could reach 6.33×10^(5) g/(mol·h),the molecular weight of EPRtype polymers was in the range of 6.27×10^(4)–40.75×10^(4) g/mol,the 1,3-enchainment content was 21%to 35%(mol),the glass transition temperature(Tg)was from–28.95℃to–40.57℃,the decomposition temperature exceeded 400℃.