Water Effects in Polymers Through Molecular Dynamics

Unless hermetically sealed, one issue that will always be a concern for any polymer used in electronics is the effect of water on the physical properties of the polymers used, and the reliability of the final composite structure. Over the years, molecular modeling has proven that it can be used in a qualitative fashion to target the most likely interface impacted by water and determine trend-wise how the adhesion or integrity will change. This paper will show specific examples of how water influences were modeled and deduced, both in pure molecular models and in scaled mesoscale models. These models demonstrate that newtonian dynamics on such a small scale is still sufficient to inform the developer how the molecular structure can impact the expected mechanical integrity such as adhesion, and how water or other molecules (that can influence interfacial properties) may arrive at an interface through diffusion. For instance, when molecular simulations of specific interfaces are targeted, the trajectories show very graphically how water interacts at the interface and serves to drop the energy resistance to an applied stress. The same may be said for the effect of water on the diffusion properties of unwanted molecules through polymer layers, however in the case of diffusion, there are issues of association/agglomeration that may impact the diffusing species. The paper will also capture work showing the scalability of molecular models up thru the coarse-grained molecular-mesoscale level (using parameters derived from molecular models), and the possibilities of scaling further.