Tack of Entangled Molecular Bottlebrushes

Polymer softness (i.e., low elastic modulus) is a known requirement for good tack in adhesives. We assess the tack performance of α-olefin molecular bottlebrushes having an elastic modulus from 4 to 30 times lower than a linear polyolefin (polypropylene). Monotonic increases of the tack parameters are observed as the bottlebrush side chain length (N_sc) increases and the modulus decreases. All-atom molecular dynamics simulations reveal that the monomeric bonding energy increases with N_sc due to a strong van der Waals interaction between the side chains and the aluminum sheet, which overcomes the energy penalty imposed by side-chain bending.