Polyethylene Containing Triblock Copolymers Synthesized by Post-polymerization Functionalization

We report the synthesis of amphiphilic triblock copolymers containing a polyethylene block as the center block. The synthetic methodology consists of performing four consecutive post-polymerization reactions on polyethylene to yield a dihydroxyl-terminated polymer. First, a cross-metathesis reaction converts the olefinic end-group of the polyethylene into an α,β-unsaturated ester followed by isomerization of the double bond and then its hydroformylation. This sequence introduces an aldehyde group randomly distributed along the polymer backbone. Finally, the reduction of the aldehyde- and ester-functionalized polymer yields two terminal hydroxyl groups. The methodology was first established using low-molecular-weight model substrates before being performed on a polyethylene with a molecular weight of M n = 13 kg mol –1 . The functionalized polyethylene was used to initiate the ring-opening polymerizations of ε-caprolactone and tert -butyl glycidyl ether to yield the corresponding triblock copolymers. Subsequent hydrolysis of the tert -butyl groups in the polyether yielded an amphiphilic polymer that formed micelles in water.