Manipulating connectivity to control fracture in network polymer adhesives

Coarse-grained molecular dynamics (MD) simulations are applied to fracture in highly cross-linked, polymer networks. Random polymer networks between t wo solid surfaces are created by simulating the dynamical cross-linking pro cess. Simple, ordered networks are constructed geometrically, which enables easy manipulation of the network connectivity. The failure strain of tensi le pull and shear simulations is related to the minimal paths through the n etwork connecting the solid surfaces. This result is confirmed by using the ordered networks to explicity vary the minimal paths over a very wide rang e. Failure strains are constructed in the ordered systems to be either larg er or smaller than the dynamically formed networks. The constraints imposed by the network connectivity control the tightness of local deformations.