Influence of polymer matrix composition and architecture on polymer nanocomposite formation: Coarse-grained molecular dynamics simulation

Coarse-grained molecular dynamics simulations of stacks of two-dimensional platelets immersed in a polymer melt were performed to investigate aspects of the polymer matrix that promote the formation of intercalated or exfoliated nanocomposite structures. Such factors include temperature, copolymer architecture, and blend composition. Increasing the polymer-sheet attractive interaction led to binding of the sheets, where individual beads simultaneously attract two neighboring sheets, thus kinetically blocking intercalation by occupying the perimeter of the affected gallery. Polymers with a small polymer-sheet attraction, but having a strongly attractive chain end (end-functionalized polymers) minimized the bonding of adjacent sheets. These systems exhibited some sheet sliding because a majority of the confined polymer beads only interacted weakly with adjacent sheets; however, the number density of intercalated polymer was low. Mixtures of end-functionalized and nonfunctionalized polymers, however, yielded better intercalation efficiency. For the mixed system, the reduced number of highly attractive beads provided sufficient interaction for intercalation to occur, enabling greater intercalation rates, less sheet-bridging, and incorporation of the nonfunctionalized polymers into the galleries. (C) 2003 Wiley Periodicals, Inc.