A detailed knowledge about the physics and chemistry of multiphase materials on different length and time scales is essential to tailor their macroscopic physical and mechanical properties. A better understanding of these issues is also highly relevant to optimize their processing and, thus, their elucidation can be decisive for their final industrial application. In this paper, we develop a new multiscale modeling method, which combines the self-consistent field theory approach with the kinetic Monte Carlo method, to simulate the structural-dynamical evolution taking place in thermoplastic elastomers, where hard glassy and soft rubbery phases alternate. Since the early seventies, it is well established that the properties of the core nanophases in these multiphase materials considerably affect their overall mechanical properties. However, recent experimental studies have clearly demonstrated that, besides the efficient handling of the core nanophases, the appropriate treatment of their interfacial region is another major challenge one has to face on the way of target-oriented development of these materials. In this work, we set a particular focus on the complex structural-dynamical processes occurring at the interphases, and study their influence on the local structural and mechanical properties. To reach our objectives, we apply the new methodology on a thermoplastic elastomer composed of ABA triblock copolymers, subjected to a sizeable external perturbation, and determine its time-averaged internal stress and composition profile. We deduce from this investigation that, to obtain the correct local mechanical properties of these multiphase materials, their structure and dynamics need to be taken into account on an equal footing. Finally, our investigation also provides an explanation and confirms the importance of the chain-pullout mechanism in the viscoelastic and stress relaxation behavior of these materials. (c) 2006 Elsevier Ltd. All rights reserved.