An MD study of the polymer–polymer adhesion via connector chains: some aspects of the competition between bulk dissipation in the interphase and pull-out of interface-connecting molecules

Abstract

Atomistic simulation approach was used to analyze the separation behavior of polymer–polymer interfaces. This was achieved using coarse-grained molecular dynamics (MD) simulations of some connector chains embedded in two adjacent polymer entangled melts. To separate the contribution of polymer molecules pull-out from the micro-bulk dissipation in the viscoplastic interphase, surrounding the surface of separation, two kinds of simulations were considered: (a), simulations of the pull-out mechanism, where the extraction of the connectors out of the melts takes place through a complex mechanism of forced reptation only; (b), simulations of the full debonding process where the micro-bulk dissipation contributes to the overall crack opening and can skew the description of the interface separation by pure connector molecules pull-out. From the MD simulation results, some relevant parameters (e.g., a cohesive strength or an adhesion energy) of the separation behavior of the interface being modelized were extracted. In addition, one was able to separate quantitatively connector pull-out from micro-bulk dissipation (in the surrounding bulk region of the interface). This means that we were able to emphasize: (i) how the straining divides into interface opening and bulk deformation and (ii), how the macroscopic opening rate diffuses throughout the melts and the interface opening rate, since the mechanical behavior of polymers is strain-rate dependent. A comparison between two kinds of MD simulations, where a system is stretched along one direction, is shortly discussed as a necessary prelude to future investigations.