Polycarbonate and Carbon Nanotube Composites: Atomistic to Meso-scale Simulation


Polymer composites are known for their improved mechanical and structural properties. Wide and diverse application of polymer composites makes it a vibrant field of study nowadays. It has become essential to investigate the change in dynamical and structural properties of polymer mixed with fillers like carbon nanotubes, nanoparticles, nanorods etc. and look into the interactions between various types of atoms at the interface in details so as to understand the basic factors which drives the change in properties. Molecular dynamics is a powerful tool to study such systems and quite useful to dig into for understanding the properties and behaviour of such composite systems. 

Polycarbonate is a widely used polymer and while embedded with fillers it exhibits change in mechanical, thermal, electrical properties. For our study, we have taken the system of monomer and trimer of polycarbonate and single wall carbon nanotube as filler. Different percentages of mixers have been taken for the study of structural and dynamical properties. Moreover we are investigating the energetics of aggregation of nanotubes in the polymer matrix.

We have performed atomistic simulation to explore local structural and dynamical properties of nanotubes in composite and then meso-scale simulation is carried out to study morphology and dynamics in experimental length and timescale. In atomistic simulation bundle formation of CNTs is observed and the mechanism and energetics of bundle formation are investigated. Bundle formation of nanotubes is found to be energetically favourable. As atomistic simulation is restricted in terms of length and timescale, simulation of long polymer chains with long nanotubes is difficult. So Dissipative Particle Dynamics simulation is performed to study the morphology and dynamics of CNTs in long chain polycarbonate matrices with different concentrations of CNT. Necessary parameters for DPD simulation of nanotube polymer composite is mapped from all-atomistic MD simulations using Flory-Huggins theory. Three different concentrations (2, 5, 10 wt. percentages) of nanotube loading in polycarbonate matrix are simulated to investigate morphology and dynamics of nanotubes. Bundle formation of nanotubes in polycarbonate matrices has been observed. In case 10% mixture, percolation morphology by nanotubes is found to be formed. We explore the dynamics of bundle formation in different mixture and bundle size distribution is studied to investigate relative bundling efficiency of nanotubes in different concentrations.

 Percolation morphology by CNTs in 10% mixture.