Molecular dynamics simulations of the elastic properties of polymer/carbon nanotube composites

Carbon nanotubes (CNTs) are promising additives to polymeric materials due to the potential for their enhancement of the structural, mechanical and electronic properties of the resulting composite. However, improvements in properties are by no means guaranteed, and the results are often sensitive to the particular polymer chosen, in addition to the quantity and quality of CNTs used in the composite. In this paper, we present classical molecular dynamics (MD) simulations of model polymer/CNT composites constructed by embedding a single wall (10, 10) CNT into two different amorphous polymer matrices: poly(methyl methacrylate) (PMMA) and poly{(m-phenylenevinylene)-co-[(2,5-dioctoxy-p-phenylene) vinylene]} (PmPV), respectively, with different volume fractions. A constant-strain energy minimization method was then applied to calculate the axial and transverse elastic moduli of the composite system. The simulation results support the idea that it is possible to use CNTs to mechanically reinforce an appropriate polymer matrix, especially in the longitudinal direction of the nanotube. In addition, the results show that detailed interfacial ordering effects cannot be ignored when interactions between the nanotube and polymer matrix are strong. The comparison of the simulation results with the macroscopic rule-of-mixtures for composite systems showed that for strong interfacial interactions, there can be large deviations of the results from the rule-of-mixtures.