Entanglement Network of the Polypropylene/Polyamide Interface. 1. Self-Consistent Field Model

We present a lattice-based self-consistent mean-field theory of polymer interfaces composed of free and grafted chains and apply it to polypropylene/polyamide interfaces strengthened with graft copolymers. The theory takes into account the molecular weight distributions and stiffnesses of all chain species present in the system and the surface density of the copolymer. As our main interest is in the terminal mechanical properties of the interface, in our model we treat the PP/PA6 interface by envisioning an equivalent “solid” PA6 substrate on which the PP chains of the copolymeric compatibilizer are terminally grafted, extending into a bulk PP phase. All parameters of the model are obtained from experimentally known properties of the PP homopolymer. We investigate the influence of the molecular weight distribution and of the surface density of the grafted chains on bond order parameters, volume fraction profiles, and chain dimensions, as well as on the width of the region where surface-grafted and bulk PP chains intermingle. Results from the theory can be used as a starting point for generating an entanglement network representative of the interfacial region.