Polyethylene-Grafted Sheet-like Silsesquioxane Nanocomposites with Unprecedented Adhesion to Polar Substrates

Polyethylene is a highly apolar polymer with very poor adhesion to most substrates, necessitating the use of tie layers. Therefore, the synthesis of functional polyethylene is a long-standing challenge in catalytic ethylene polymerization. Here, we report the preparation of a nanocomposite comprising polyethylene covalently grafted onto sheet-like silsesquioxanes, with unprecedented adhesion to metal and glass. A norbornene-grafted, layered Mg-silsesquioxane is treated with Grubbs second-generation catalyst (G-II), and the identity of covalently tethered G-II is unambiguously ascertained. Covalently tethered G-II catalyzes the ring opening metathesis polymerization of cyclooctene to poly(cyclooctene). The resulting poly(cyclooctene) is catalytically hydrogenated to yield polyethylene. This polyethylene nanocomposite exhibited a bonding strength of the order of 100 MPa on stainless steel and aluminum, 10-fold higher than reported for engineered polyethylene copolymers. The nanocomposite exhibits an increase in the polar component of surface energy, yet remains compatible and cocrystallizes with a polyethylene matrix.