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 alpha-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 (Nsc) increases and the modulus decreases. All-atom molecular dynamics simulations reveal that the monomeric bonding energy increases with Nsc 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.

Automated summary

Polymer softness is important for good tack in adhesives. We studied the tack performance of alpha-olefin molecular bottlebrushes with a lower elastic modulus compared to linear polyolefin. The tack parameters increased as the bottlebrush side chain length increased and the modulus decreased. Molecular dynamics simulations showed that the bonding energy increased with side chain length due to strong van der Waals interactions between the side chains and the aluminum sheet.