Modeling of Polyethylene and Functionalized CNT Composites: A Dissipative Particle Dynamics Study

Dissipative particle dynamics (DPD), a mesoscopic simulation approach, has been used to investigate the effect of volume fraction, the different degree of functionalization, and the effect of PE length on the structural property of the immiscible polyethylene (PE)/carbon nanotube (CNT) in a system. In this work, the interaction parameter in DPD simulation, related to the Flory−Huggins interaction parameter, χ, is estimated by the calculation of mixing energy for each pair of components in molecular dynamics (MD) simulation. The immiscibility property of CNT and PE polymer induces the phase separation and exhibits different architectures at different volume fractions. In order to observe the effects of different degrees of functionalization, we change the repulsive interaction parameter to simulate the different degrees of functionalization. In order to observe the effect of volume fraction and different degrees of functionalization, the radius of gyration and order parameter are used to observe the arrangement of the polymer chains and CNT, respectively. We find that different degrees of functionalization will affect the final equilibrium structure significantly when the volume fraction of CNT is lower than 50%. We also find that the microstructure arrangement of PE is dependent on the equilibrium phase. Finally, for a shorter PE chain system, we only need to decrease the repulsive interaction parameter slightly in order to distribute the CNT and the PE in the system. In addition, it should be noted that different interaction parameters do not relate to any real functional group, but only present different interaction degree in the simulation, which can reflect the different chemical functionalizations.