2014-11-26
10:15 at HCI J 574

Development of scale-bridging methodologies for the reliable prediction of the viscoelastic properties of polymer melts

Pavlos S. Stephanou

Department of Mathematics and Statistics, University of Cyprus

Polymeric chains are characterized by a broad spectrum of length and time scales, which gives rise to properties that are totally different from those of the simple Newtonian liquids, especially under flow conditions. Our aim is to contribute to the understanding of the complex interplay between microscopic chain configurations or conformations and macroscopic behaviour, which is a central goal in polymer science and technology and a prerequisite for the design of improved polymers tailored for specific applications. Guided from the reptation theory of de Gennes and Doi/Edwards, we will first show how one can predict the linear viscoelastic properties of polymer melts by using atomistic trajectories from detailed MD simulations to calculate the primitive path (PP) segment survival probability function ψ(s,t) for entangled melts, both for mono and bidisperse polymers. This function is at the heart of the Doi/Edwards reptation theory but also of all tube models. Next, we will show how one can use modern formalisms of non-equilibrium thermodynamics to construct differential constitutive equations for polymer melts. Our emphasis here will be on the derivation of a set of dynamic equations describing in a unified way the microstructure, the linear and nonlinear rheology, and the phase behaviour of polymer melts filled with nanoparticles (also known as polymer nanocomposite melts).