Exfoliation of stacked sheets: Effects of temperature, platelet size, and quality of solvent by a Monte Carlo simulation
Can a layer of stacked sheets (coarse grained description of clay platelets) exfoliate in a given solvent? Computer simulations are performed to address this question with a stacked layer of four sheets. A sheet is described by a set of nodes (N) tethered to gether by flexible (fluctuating) bonds in a planar structure with linear scale L-s, N = L-s(2) on a cubic lattice of size L-3. The initial distance between the sheets is small and kept constant for different sets of stacked sheets. Quality of the effective solvent is controlled by a short range interaction (c) between sheets, that is, their nodes and the empty lattice sites (epsilon = -2, -1, 1, 2). Nodes execute stochastic movement with the Metropolis algorithm subject to bond fluctuation and excluded volume constraints. Simulations are also performed at different temperatures. Visual analysis shows that the exfoliation depends on the size of the sheet and temperature. We find that it is easier to exfoliate smaller sheets and that the exfoliation is enhanced by raising the temperature. The exfoliation becomes very slow for large sheets at low temperatures because of longer relaxation times. Exfoliation is enhanced by increasing the attractiveness (i.e., the quality) of the solvent interaction with the platelets. (c) 2006 Wiley Periodicals, Inc.