双(水杨醛亚胺)镍配合物催化乙烯-甲基丙烯酸甲酯共聚

Copolymerization of Ethylene and Methyl Methacrylate by Bis-(salicylaldiminato)Nickel(Ⅱ)Complexes

研究了3个在苯胺基邻位含有不同位阻效应的双(水杨醛亚胺)镍配合物C1~C3的合成及其结构的分析与表征。在助催化剂甲基铝氧烷(MAO)作用下,以C3为主催化剂,考察了Al与Ni物质的量之比(nAl/nNi)、催化剂用量、反应温度、压力、甲基丙烯酸甲酯(MMA)浓度、时间等对乙烯与甲基丙烯酸甲酯共聚的影响,得到最佳聚合条件为:nAl/nNi为150,温度25℃,压力2MPa,反应时间2h。在此条件下评价了C1、C2和C3催化剂结构对聚合反应的影响,发现在苯胺基邻位的取代基位阻较小时,催化活性较好,但所得聚合物分子量较低,并对共聚物结构进行了1 H-NMR、13C-NMR、FT-IR等分析和表征。

Three bis-（salicylaldiminato）nickel（Ⅱ）complexes with different steric hindrances on the adjacent position of aniline group,[O-（3,5-I2）C6H3-o-C（H）N-2,6-C6H3（Me）2]2 Ni（C1）,[O-（3,5-I2）C6H3-o-C（H）-N-2,6-C6H3（Et）2]2 Ni（C2）and [O-（3,5-I2）C6H3-o-C（H）-N-2,6-C6H3（i-Pr）2]2 Ni（C3）,were successfully synthesized based on the reaction of Ni（CH3 COO）2·4 H2 O with ligands L1—L3,HO-（3,5-I2）C6H2-o-C（H） N-2,6-C6H3（Me）2（L1）,HO-（3,5-I2）C6H2-o-C（H） N-2,6-C6H3（Et）2（L2）and HO-（3,5-I2）C6H2-o-C（H） N-2,6-C6H3（i-Pr）2（L3）.The ligands were characterized by 1 H-NMR and FT-IR,and the formed complexes were characterized by 1 H-NMR,FT-IR,element analysis（EA）and mass spectrometry（MS）.The complexes were applied for copolymerization of ethylene and methyl methacrylate（MMA）in the presence of methylaluminoxane（MAO）. The effects of different polymerization factors,such as Al、Ni molar ratio（nAl/nNi）,catalyst dosage,polymerization reaction temperature and ethylene pressure,the concentration of MMA and polymerization reaction time were investigated systematically.The optimum polymerization conditions were as follows：nAl/nNi150,25 ℃,ethylene pressure of 2 MPa and 2 hpolymerization.With the increase of nAl/nNi,the catalyst activity first increased and then decreased.The more catalyst dosage uses,the higher molecule mass was obtained.The activity increased with the increasing of polymerization pressure.The increases of polymerization time led to an increase followed by a decrease of catalyst activity.The complexes C1—C3 were evaluated for the copolymerization under the optimum polymerization conditions.The complex C1 with small substituents on the adjacent position of aniline group displayed higher catalytic activity of 12.2 kg/（mol·h）,but lower molecular mass of 5.97×10^5.While C2 and C3 with bulky substituents on the adjacent position of aniline group showed low catalytic activity,6.8 kg/（mol·h）and C3 5.4 kg/（mol·h）respectively,and high molecular mass with 8.06×10^5 for C2 and 9.85×10^5 for C3.The microstructures of the obtained polymers were characterized by ^1 H-NMR,^13 C-NMR and FT-IR spectra,demonstrating that the polymers were the copolymers of ethylene and MMA.