(561f) A Multiscale Strategy for Predicting Radiation Damage in Polymers | AIChE

(561f) A Multiscale Strategy for Predicting Radiation Damage in Polymers


Kroonblawd, M. - Presenter, Lawrence Livermore National Laboratory
Yoshimura, A., Lawrence Livermore National Laboratory
Goldman, N., Lawrence Livermore National Laboratory
Maiti, A., Lawrence Livermore National Laboratory
Lewicki, J., Lawrence Livermore National Laboratory
Saab, A., Lawrence Livermore National Laboratory
Polymers are routinely subjected to ionizing radiation as a means for sterilization, as part of planned operation conditions, and as a driver to accelerate aging. Chemical reactions resulting from this exposure can alter polymer networks, leading to undesirable macroscale degradation such as permanent set. A primary mode for radiation damage arises from ballistic electrons that induce electronic excitations, but subsequent chemical mechanisms are poorly understood. We develop a multiscale modeling strategy to predict this chemistry starting from subatomic scattering calculations. Ensembles of nonadiabatic molecular dynamics simulations based on time-dependent density functional theory are used to sample initial bond-breaking events following the most likely excitations. These excited state configurations in turn feed into semiempirical quantum-based simulations of the approach towards chemical equilibrium. Application of our approach to polyethylene shows that local backbone conformation plays a significant role in the initial steps of radiolysis, providing a plausible explanation for experimental observations of a morphology dependence in network crosslinking. Statistical and graph-analysis techniques are described that cast quantum simulations as an easy-to-implement test of degradative chemical reaction schemes.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Approved for unlimited release, LLNL-ABS-833130.