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 BR₂, OH, NH₂, OSi(CH₃)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 (Cp₂ZrCl₂ [bis(cyclopentadienyl) zirconium dichloride] and Et(Ind)₂ZrCl₂ [1,1′‐ethylenedi‐η⁵‐indenyl‐zirconium dichloride] with MAO (methylaluminoxane)) and one heterogeneous (TiCl₃·AA/Et₂AlCl) ones, were studied in the copolymerization reactions. The single site Et(Ind)₂ZrCl₂/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.