Allene Polymerization Catalyzed By Vanadium Complex Containing Bulky Aryloxo Ligand

Allene is a 1,2-propadiene derivative with accumulated double bonds.Due to its unique structure,the electron cloud density of the three carbon atoms on the two double bonds is different,so it has a variety of reactivity and selectivity.Combining the unique chemical structure of allenes with ethylene to obtain functionalized polyolefins has attractive development prospects.Based on the research foundation of this research group on polyolefins,this thesis designed and synthesized seven high transition state vanadium complexes（V）with different electronic effect substituents and steric structures.The designed and synthesized vanadium complexes were employed as pre-catalyst for allene polymerization.Different alkyl aluminum reagents were used as co-catalysts for homo-polymerization of allene derivatives,norbornene,ethylene and the copolymerization of allene and ethylene respectively.First,we selected the typical phenyl allene monomer as the research object and screen the influence of different polymerization conditions on the reaction.Also a series of allene homopolymers with different types of allene derivative monomers were studied to unclose the reaction between vanadium complex and allene.The reactivity between double bonds is tested and characterized by ¹H NMR,¹³C NMR,GPC,FT-IR,DSC,TGA,etc.The analysis results found that the obtained polyphenylallene has very good 2,3-regioselectivity（>99%）.High molecular weight PPA（M_n=740 k Da）can be obtained under the polymerization conditions of high monomer concentration.Subsequently,we studied the catalytic performance of vanadium complexes on norbornene and ethylene,and the results showed that the catalytic reactivity toward norbornene was relatively low,but the vanadium complex C4 had a high trans-selectivity to the ROMP of NBE（>95%）.Whereas the reported vanadium complexes give the cis and trans mixtures in Poly-NBE.In addition,the designed of vanadium complex exhibits extremely high catalytic activity in the polymerization of ethylene,up to 1.01×10⁶ g-PE/mol-V·h.Also in the copolymerization of ethylene and allene monomers by vanadium complex could give the corresponding copolymer.