Morphology, Structure and Dynamics of Ionic Polydimethylsiloxane-Silica Nanocomposites

We designed ionic polydimethylsiloxane (PDMS)-silica nanocomposites from (cationic) ammonium-functionalized PDMS and (anionic) sulfonate-functionalized nanosilicas, with the aim of influencing the distribution and dispersion of the nanoparticles. The impact of the PDMS molecular weight, charge density and charge location on the distribution, dispersion of ionic nanosilicas and on the mechanical reinforcement of the nanocomposites is explored. Self-healing property arises from reversible ionic interactions located at the interface between PDMS matrix and nanosilicas. We use coarse grained equilibrium molecular dynamics to model ionic nanocomposites and to investigate their behavior, in particular, polymer conformations, entanglements and dynamics for different loadings, for two types of charge-sequenced polymers at two different Bjerrum lengths. We calculate the lifetimes of temporary ionic crosslinks that are created between ionic nanoparticles and polymers. Non equilibrium molecular dynamics is used to investigate the stress - stress behavior, ionic crosslinks and entanglements under deformation.