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Polymer/polymer interfaces reinforced with block copolymers or grafted chains can fail by the pull-out of these chains. A number of constitutive models have been proposed in the literature to describe the pull-out of a single chain. In this paper, we use these models to construct a continuum theory of a weak interface, and we study the stability of such an interface subjected to a homogeneous deformation. We show tht if the perturbation contains a Fourier component with wavelength exceeding a critical value Λc, then the homogeneous deformation is unstable. The dependence of Λc on the geometry, the stiffness of the material outside the interface, and the pull-out models is derived. We also study the stress field near the tip of a preexisting interface crack using the different pull-out models.

In this paper, we study the relationship between crack nucleation and failure of an interface reinforced by chains and the results of a linear stability analysis presented in part 1 of this study (preceding paper in this issue). We develop a numerical procedure to simulate the deformation and failure of such an interface. We demonstrate that instabilities lead to spatial localization of the deformation which determines the failure mode of the interface. The dependence of the failure modes on the material parameters of the system, such as the number of entanglements of the pull-out chains, the level of applied load, and the amplitude of the initial perturbation, is studied.