Computer simulation of nylon-6/organoclay nanocomposites: prediction of the binding energy

Molecular mechanics/dynamics computer simulations are used to explore the atomic scale structure and to predict binding energy values for polymer/clay nanocomposites based on nylon-6, montmorillonite (MMT) and several, different quaternary ammonium salts. Our results reveal that the energy of binding between the polymeric matrix and the montmorillonite platelet shows a decreasing trend with increasing molecular volume V of the quaternary ammonium salt used as surfactant. On the other hand, both the binding energy between the polyamide and the quat, and between the quat and the montmorillonite increase with increasing V, although with a different slope. Shorter hydrocarbonic chains are more effective in producing favorable binding energies with respect to longer ones, and the substitution of hydrogen atoms with polar groups, such as –OH or –COOH on the quaternary ammonium salt generally results in a greater interaction of the quat with the polymer. Finally, under the hypothesis that the clay platelets are uniformly dispersed within the polymer matrix, the pristine clay still yields a high interfacial strength between MMT and nylon-6.