Preliminary Molecular Dynamics Studies of the Montmorillonite, Amylose, Fatty Acids and Water for Polymer-Clay Nanocomposite Modeling

This work shows a part of a theoretical study of Polymer-Clay Nanocomposites (PCN) formed by an acetylated amylose segment and fatty acids present in the Pequi oil, a fruit from the Brazilian Cerrado, in aqueous medium, including or not, organophilized montmorillonite (MMT-O). The simulated systems aim to provide qualitative information about the molecular movement among diverse chemical species; their structural and behavioral correlations and essential intermolecular forces. The calculations were carried out by Molecular Mechanics and Dynamics methods with the Polymer Consistent Force Field-interface. Simulation results had shown behavioral differences between systems. Without MMT-O, the acetyl amylose residues quickly became coiled, most of the fatty acids cover its surface, and water molecules are stabilized over the polysaccharide portions free of fatty acids. With MMT-O the fatty acids show a potential plasticizing effect due to the greater compatibility between the components of the studied system, since the organic assemblage is strongly attracted by the electrostatic force of the clay. Besides, water molecules flow to the clay layer, while the non polar portion of fatty acids increase their flexibility, in spite to stay attached to acetyl amylose, progressively coiled, through hydrogen bonds. This behavior is interpreted as an improvement in the miscibility of the oil. The new knowledge acquired about these molecular systems encourages us to increase the models complexity, and undertake further studies in the design of PCNs with biopolymers.