Large-scale simulation of adhesion dynamics for end-grafted polymers

The adhesion between a polymer melt and substrate is studied in the presence of chemically attached chains on the substrate surface. Extensive molecular dynamics simulations have been carried out to study the effect of temperature, tethered chain areal density (Σ), tethered chain length (Nt), chain bending energy (kθ), and tensile pull velocity (v) on the adhesive failure mechanisms of pullout and/or scission of the tethered chains. We observe a crossover from pure chain pullout to chain scission as Nt is increased. Below the glass transition, the value of Nt for which this crossover begins approaches the bulk entanglement length Ne. For the values of Nt and Σ used here, no crossover to crazing is observed.