新型镍二亚胺配合物/甲基铝氧烷催化剂催化丙烯酸甲酯聚合

2,6-二异丙基苯胺经浓硝酸硝化,硝化产物3-硝基-2,6-二异丙基苯胺与乙二醛通过Schiff碱缩合反应,合成了N,N′-二(3-硝基-2,6-二异丙基苯基)乙二亚胺配体,该配体直接与无水氯化镍反应制得N,N′-二(3-硝基-2,6-二异丙基苯基)乙二亚胺二氯化镍配合物。采用核磁共振光谱、傅里叶变换红外光谱及元素分析的方法对配体和配合物进行了表征。在甲基铝氧烷的助催化作用下,研究了以该配合物为主催化剂催化丙烯酸甲酯聚合反应的机理,考察了催化剂浓度、聚合温度、聚合时间、n(Al)∶n(Ni)等因素对聚合反应的影响,得到最佳聚合条件:催化剂浓度0.7mmol/L、n(Al)∶n(Ni)=250、聚合温度35℃、聚合时间2h。在此条件下,聚合物相对分子质量为2.41×104,催化剂活性为23.2kg/(mol.h)(以每小时每摩尔Ni生成的聚丙烯酸甲酯质量计)。

Polymerization of Methyl Acrylate with Novel Nickel α-Diimine Complex/ Methylaluminoxane Catalyst

N,N′-bis-(3-nitro-2,6-diisopropylphenyl)-ethanediimine nickel dichloride complex, used in catalyst system of methyl acrylate polymerization, was synthesized by reaction of anhydrous nickel dichloride with N,N′-bis-(3-nitro-2,6-diisopropylphenyl)-ethanediimine ligand. The latter was obtained by Schiff base condensation of 3-nitro-2,6-diisopropyl aniline with glyoxal. 3-Nitro-2,6-diisopropyl aniline was prepared by nitration of 2,6-diisopropyl aniline with concentrated nitric acid. Both the ligand and complex were characterized by means of 1H NMR, FTIR and elemental analysis. Polymerization of methyl acrylate with above prepared complex as catalyst and methylaluminoxane(MAO) as cocatalyst was studied. The optimal conditions and mechanism of polymerization were investigated. Effects of complex concentration, polymerization temperature, polymerization time and mole ratio of aluminum to nickel were studied. Under optimal conditions: catalyst concentration 0.7 mmol/L, polymerization time 2 h, polymerization temperature 35 ℃ and n(Al) ∶n(Ni) 250, relative molecular mass of the polymer is 2.41×104 and activity of catalyst is 23.2 kg/(mol · h).