Modeling of PDMS - Silica Nanocomposites

A hydrogen bonding pathway between polydimethylsiloxane (PDMS) and hydroxyl groups on a silica surface was studied using quantum chemistry calculations of disiloxane and hexamethyldisiloxane molecules with small silica clusters. A newly developed classical force field for PDMS was developed for atomistic molecular dynamics simulation studies of PDMS – silica nanocomposites to determine the effect of these interactions on the dynamics and structure of PDMS. A three nanometer silica particle ( -crystobalite) with (111) surface hydroxyl group density of 4.8 OH groups/nm was simulated in a PDMS melt in the temperature range of 300 to 500K. The density and structure of PDMS chains near the silica surface were strongly influenced by the hydrogen bonding interaction which is not properly represented in other current force fields. Residence time correlation analysis confirmed that PDMS oxygen – silica surface hydrogen atom dynamics were consistent with polymer hydrogen bonding.