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合成了4种α-二亚胺镍催化剂Ar—NC(R1)C(R2)N—ArNiBr2[Ar=2,6-dimethylphenyl,R1=CnH2n+1,R2=CmH2m+1;其中Cat1:m=1,n=1;Cat2:m=2,n=1;Cat3:m=3,n=1;Cat4:m=2,n=2],考察了聚合温度、催化剂浓度和催化剂配体骨架碳原子上烷基取代基对乙烯聚合反应活性、聚合物链结构和结晶性能的影响.实验发现,当配体骨架上烷基取代基R1和R2不同时,催化剂具有较高的活性,且聚合物分子量也较高;其中,Cat2和Cat3在20℃,乙烯常压和5.8mmol/L催化剂用量下,乙烯聚合活性达1.86×103kgPE/(molNi.h)和1.92×103kgPE/(molNi.h),聚合物分子量(Mw)达6.82×105和1.019×105.聚乙烯链结构分析表明,甲基支链在聚乙烯支链中占主导地位,支化度主要受反应温度的影响;同时还发现,配体骨架碳原子上烷基取代基不同的二亚胺镍催化合成聚乙烯的长支链比例相对较高,特别是在较高反应温度40℃下,己基及以上长支链比例明显增加.
Four kinds of α-diimine nickel catalysts Ar-NC (R1) C (R2) N-ArNiBr2 [Ar = 2,6- dimethylphenyl, R1 = CnH2n + 1, R2 = CmH2m + Cat 2: m = 2, n = 1; Cat 3: m = 3, n = 1; Cat 4: m = 2, n = 2]. The polymerization temperature, catalyst concentration, The influence of the alkyl substituents on the polymerization of ethylene, the polymer chain structure and the crystallization behavior was investigated. It was found that when the R1 and R2 alkyl substituents on the ligand were different, the catalyst had high activity. And the polymer Among them, Cat2 and Cat3 had ethylene polymerization activity of 1.86 × 103kgPE / (molNi.h) and 1.92 × 103kgPE / (molNi.h) at 20 ℃, ethylene pressure of 5.8mmol / L and catalyst dosage of 5.8mmol / The molecular weight (Mw) of the polymer reached 6.82 × 105 and 1.019 × 105. The analysis of the structure of the polyethylene chain showed that the methyl branch was dominant in the branch of polyethylene and the degree of branching was mainly affected by the reaction temperature. The proportion of long chain branch of polyethylene catalyzed by nickel imide with different alkyl substituents on the carbon atom of the ligand skeleton is relatively high. Especially at the higher reaction temperature of 40 ℃, the proportion of long chain branches of hexyl and above obviously increases.