A MOLECULAR MECHANICS STUDY ON THE EFFECT OF SURFACE MODIFICATION ON THE INTERFACIAL PROPERTIES IN CARBON NANOTUBE/POLYSTYRENE NANOCOMPOSITES

We have developed a molecular mechanics approach to study surface modification and its effect on the mechanics of interfaces in nanocomposites. Investigation of this topic is motivated by the exceptional mechanical properties that have been demonstrated in a new generation of nanomaterials. The systems studied mainly include polystyrene polymers that are reinforced by carbon nanotubes subjected to different surface modifications. The interactions among the atoms in the system are governed by the empirical potentials in the form of force fields. To directly probe the interfacial mechanics, a nanotube pull-out test is simulated. The interfacial properties between the carbon nanotube and polystyrene matrix are evaluated from the numerical experiments under different surface modification conditions. The simulation results show that both the interfacial energy and interfacial shear stress can be improved significantly by introducing a functional group on the surface of the carbon nanotube. Interfacial strength up to 486 MPa can be achieved with the employed surf-ace modification. The simulation also indicates the existence of an optimum functional ratio in terms of the energy barrier for interfacial sliding.