Simulations of materials are required for estimating physical or chemical, static or dynamic properties of interest prior to synthesis and experimentation. Polymers are larger in size compared to inorganic materials and therefore, the cost and energy requirement for computation are higher. Therefore, polymers are the class of materials where multi-scaling is necessary for determining their properties on real time and length scales.
Polymers in blends or composites are widely used for packaging food, electronics, pharmaceuticals, etc. In order to design and develop better barrier materials, simulating the diffusion properties of gases such as H2O and O2 help understanding and estimating the resultant barrier properties. However, due to the limitation on time scales of ab-initio simulations, it is required to model the system hierarchically and determine the diffusivities comparable to the properties of real systems. Therefore, a blend composite system with two polymers and a nano filler is simulated using molecular dynamics and first principle calculations. The binary interaction energies are determined to estimate interaction parameters between any of the two components. These values are further used to build a system with beads. The unit cell is built with the scaled molecular units known as beads, retaining the ab-initio molecular interactions. The system is subjected to dissipative particle dynamics (DPD) and the diffusion coefficients for H2O and O2 beads are determined through various compositions of the composite systems. Further, the trends from multi-scale simulations are compared to experimental results for validating the simulation approach.