Mechanical and dynamic properties of resin blend and composite systems: A molecular dynamics study

Molecular characterization of polymer resin systems is significantly important in prediction and advancing understanding of properties and phenomena of resin-based composites. In this work, molecular dynamics simulations of a resin composite model, i.e., silica nanoparticle reinforced Bis-GMA/TEGDMA resin composite, were performed to investigate the effects of organic and inorganic components on the structure and properties of the resulting composites. It was revealed that even a small amount of silica nanoparticles (up to 10 wt%) could improve the mechanical properties considerably due to increased intermolecular hydrogen bonds and polymer chain contraction. The reinforcement effect induced by silica nanoparticles is much more intensive than that caused by the stiff resin monomer of Bis-GMA. The composite modulus, increasing with the silica nanoparticle content, was further compared with micromechanics methods and exhibited good agreement with the Counto model, indicating strong matrix-particle interactions. Moreover, it was found that the diffusion dynamics of the resin matrix is significantly suppressed at higher contents of Bis-GMA or silica nanoparticles, which signifies a strong dependence on the hydrogen bonds and chain conformational changes. The findings in this work are believed to provide the atomic/molecular scale understanding of the structures and performances of Bis-GMA/TEGDMA resin blend and composite systems.