Effect of end-tethered polymers on surface adhesion of glassy polymers

The adhesion between a glassy polymer melt and substrate is studied in the presence of end-grafted chains chemically attached to the substrate surface. Extensive molecular dynamics simulations have been carried out to study the effect of the areal density Sigma of tethered chains and tensile pull velocity v on the adhesive failure mechanisms. The initial configurations are generated using a double-bridging algorithm in which new bonds are formed across a pair of monomers equidistant from their respective free ends. This generates new chain configurations that are substantially different than the original two chains such that the systems can be equilibrated in a reasonable amount of cpu time. At the slowest tensile pull velocity studied, a crossover from chain scission to crazing is observed as the coverage increases, while for very large pull velocity, only chain scission is observed. As the coverage increases, the sections of the tethered chains pulled out from the interface form the fibrils of a craze that are strong enough to suppress chain scission, resulting in cohesive rather than adhesive failure. (C) 2003 Wiley Periodicals, Inc.