All-atom molecular dynamics simulations of amorphous, crosslinked PDMS

The structure, dynamics, and self-diffusion properties of an amorphous, binary mixture of large poly(dimethylsiloxane) (PDMS) and small poly(hydromethylsiloxane) (PHMS) are characterized with atomic-level molecular dynamics simulations. Molar masses and mixing properties are comparable and relevant to commerical products, and simulations require massively parallel molecular dynamics simulations. The system consists of 100 vinyl-terminated PDMS molecules ($\sim$72,500 g/mol) and 200 crosslinker PHMS molecules ($\sim$1960 g/mol), for a total of more than 1 million atoms. Molecular diffusion is studied as a function of temperature, electric field, and end-crosslinking density. Simulation results provide an atomic-level description for molecular motion and an understanding of the local structure that contributes to molecular self-diffusion.