Authors: R.C. Picu
Affilation: Rensselaer Polytechnic Institute, United States
Pages: 395 - 398
Keywords: polymer dynamics, stress relaxation, polymer molecular structure
A new framework is being developed to describe stress production and relaxation in dnse polymeric systems. Stress is traditionally defined on the molecular scale, with the chaines being regarded as entropic springs. In this view, the polymeric chains are considered to be always in tension and stress is due exclusively to bonded interactions along the chains. Stretching the chains leads to a retractive force of an entropic nature. Non-bonded interactions between atoms belonging to neighboring chains are considered to lead to hydrostatic stress only. The new description is defined on the atomic rather than on the molecular scale. It takes into account all (bonded and non-bonded) interactions, and makes no apriori assumption about the behavior of any component of the system. Since it is defined on the atomic scale, the description captures all fast and slow relaxatio modes that correspond to short and long wavelength perturbations, respectively. It is therfore equally applicable to small and large volumes of material and to short and long chaings. This report presents a bried overview of this new framework. It is discussed which assumptions made inth e molecular theory are justified by atomistic simulation results and which are not. It is shown that both theories are in qualitative agreement with th experimentally observed physical picture, while the atomic scale description offers the advantages mentioned above.
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