Molecular modeling of polymer clay nanocomposites: Lysine and arginine in montmorillonite

CHED 271

Lorena Tribe, lut1@psu.edu, Alicia Davis, and Gary Joanis. Division of Science, Penn State Berks, Tulpehocken Rd., Reading, PA 19610
The interactions of the amino acids arginine and lysine with sodium montmorillonite were studied using theoretical molecular modeling methods. The interlayer spacing of montmorillonite was increased by incorporating water molecules and allowing the system to evolve with molecular mechanics. Care was taken to retain the sodium cations in the interlayer. The amino acid conformations were obtained by surrounding the molecules with numerous discrete water molecules and minimizing the system at the semi empirical level. The optimized amino acids were then placed in the interlayer space in a series of initial positions. Molecular mechanics calculations were performed and the final positions were analyzed. The results tend to indicate the preponderance of configurations which include surface-sodium-amino acid complexes. This result is compared with molecular dynamics calculations of elastic properties of these systems from the literature.