(167o) Atomistic Simulation Study of a Polycarbonate/Silica Composite System: Dynamics of the Interphase

Polymer composites ideally combine the advantageous mechanical properties of a fiber or filler material with a polymer matrix material. This combination makes for a strong and durable material that also has an improved strength to weight ratio. The mechanical reinforcement by the filler relies on the transfer of loading from the matrix to the filler material where molecular scale interactions play a role in the overall strength of the composite. Load transfer depends upon the bonding of the filler and matrix, defining the interface, and also upon modifications of the matrix material from its bulk behavior near the interface, defining the interphase region. Here, we use atomistic molecular dynamics (MD) to model a composite system, specifically polycarbonate (PC) confined between silica surfaces, to determine how the structure and dynamics of the PC matrix material is modified by confinement by these specific molecular interactions. We measure and compare PC structure and dynamics as a function of distance from the silica surface and also compare the matrix properties to a bulk PC system to detect and quantify signatures of the interphase region and how dynamics are affected by confinement. The interfacial dynamics of PC are used to interpret how behavior introduced by the presence of the silica might influence properties such as toughness based on various types of evidence from experimental measurements. We also study the influence of the cooling rate upon the growth, dynamics, and chain conformation in interphase region.