Functionalization of polyethylene using borane reagents and metallocene catalysts

A new method to prepare functionalized polyethylene involving borane intermediates and transition metal catalysts is described. Two processes, direct and post polymerizations, were employed to prepare borane-containing polyethylene (PE-B), which can be transformed to functionalized polyethylene (LLDPE-f) with various functional groups, such as -BR 2 , -OH, -NH 2 , -OSi(CH 3 ) 3 . In the direct process, the PE-B copolymers were prepared in one step by copolymerization of ethylene with a borane monomer (ω-borane-α-olefin). The post polymerization process requires two steps : copolymerization of ethylene and 1,4-hexadiene, and subsequential hydroboration reaction of unsaturated PE. Three transition metal catalysts, including two homogeneous metallocene (Cp 2 ZrCl 2 [bis(cyclopentadienyl) zirconium dichloride] and Et(Ind) 2 ZrCl 2 [1,1'-ethylenedi-η 5 -indenyl-zirconium dichloride] with MAO (methylaluminoxane)) and one heterogeneous (TiCl 3 .AA/Et 2 AlCl) ones, were studied in the copolymerization reactions. The single site Et(Ind) 2 ZrCl 2 /MAO homogeneous catalyst, with a strained ligand geometry and opened active site, is by far the most effective system in the incorporation of high olefins into polyethylene structures.