Molecular Dynamics simulations using Cerius2 software package were used to study the static and dynamic properties of 2:1 layered silicates ion-exchanged with alkyl-ammonium surfactants.
Figure 1. Schematic of the polymer layered silicate nanocomposite (PLSN) morphologies: (a) intercalated and (b) exfoliated.
Examining Static and Dynamic Properties of Polymer-Silicate Nanocomposites
Polymer-silicate nanocomposites exhibit good mechanical and thermal properties, and can be used in a variety of applications. Molecular dynamics simulations using Cerius2 software package were used to study the static and dynamic properties of 2:1 layered silicates ion-exchanged with alkyl-ammonium surfactants.
Optimizing Design of Polymer-Silicate Nanocomposites
By studying the systems at the experimentally measured layer separations, computer modelling provides the structure and dynamics of the intercalated surfactant molecules, which can assist in the design of polymer-silicate nanocomposite systems.
Challenge in Developing Nanocomposites
A major challenge in developing nanocomposites for systems ranging from high-performance to commodity polymers is the lack of even simple structure-property models. Without such models, progress in nanocomposites has remained largely empirical. The large internal interfacial area between the polymer and the silicates together with the nanoscopic dimensions between nanoelements differentiates Polymer Nanocomposites (PNCs) from traditional composites and filled plastics.
Atomic Level Structure of Nanocomposites
Monte Carlo and molecular dynamics simulation give insight into the structure of nanocomposites on the atomic level. Figure 2 reveals that when confined to a nanoscale gap or near a surface, the polymer chains order into discrete subnanometer layers. This is useful in understanding the intercalation process and the source of some macroscopic properties such as ionic conductivity. Knowledge gained from simulations can be used to better engineer the polymer-silicate interaction.
Figure 2. (a) Molecular Dynamics simulation ‘snapshot’ of a silicate-surfactant-polystyrene nanocomposite. (b) The corresponding ensemble-averaged, number density of carbon atoms as a function of distance.