Argyrios Karatrantos

Modeling of Polymer Structure and Conformations in Polymer Nanocomposites from Atomistic to Mesoscale: A Review

ABSTRACT Over the past two decades polymer nanocomposites have received tremendous interest from industry and academia due to their advanced properties comparative to polymer blends. Many computational studies have revealed that the macroscopic properties of polymer nanocomposites depend strongly on the microscopic polymer structure and conformations. In this article we review computer simulation studies of the fundamental problem of homopolymers structure and dimensions in nanocomposites containing bare or grafted spherical or rod nanoparticles. Experimentally, there is controversy over whether the addition of nanoparticles in a polymer matrix can perturb the polymer chains.

Topological entanglement length in polymer melts and nanocomposites by a DPD polymer model

We investigate the topological constraints (entanglements) in polymer–nanorod nanocomposites in comparison to polymer melts using dissipative particle dynamics (DPD) polymer model simulations. The nanorods have a radius smaller than the polymer radius of gyration and an aspect ratio of 7.5. We observe an increase in the number of entanglements (50% decrease of Ne with 11% volume fraction of nanorods dispersed in the polymer matrix) in the nanocomposites as evidenced by larger contour lengths of the primitive paths. The end-to-end distance is essentially unchanged with the nanorod volume fraction (0–11%). Interaction between polymers and nanorods affects the dispersion of nanorods in the nanocomposites.

Polymer and spherical nanoparticle diffusion in nanocomposites

Nanoparticle and polymer dynamics in nanocomposites containing spherical nanoparticles were investigated by means of molecular dynamics simulations. We show that the polymer diffusivity decreases with nanoparticle loading due to an increase of the interfacial area created by nanoparticles, in the polymer matrix. We show that small sized nanoparticles can diffuse much faster than that predicted from the Stokes-Einstein relation in the dilute regime. We show that the nanoparticle diffusivity decreases at higher nanoparticle loading due to nanoparticle-polymer interface. Increase of the nanoparticle radius slows the nanoparticle diffusion.

Primitive path network, structure and dynamics of SWCNT / polymer nanocomposites

We investigate the entanglements, structure and dynamics of monodisperse polymer melts in the presence of a single wall carbon nanotube (SWCNT) in comparison to inclusion-free polymer melts by molecular dynamics simulations. The SWCNT has an infinite aspect ratio and radius smaller than the polymer radius of gyration. In the presence of SWCNT with or without attractive interactions, the contour length of the primitive path increases indicating more entanglements. We also find that the overall configuration, as characterized by the radius of gyration, is not perturbed by either the interaction energy between the polymer and the SWCNT or by variations in the SWCNT radius. We also find that there is a large heterogeneity in the polymer dynamics of the polymer melts with a SWCNT due to the polymers in contact with the SWCNT.

Structure, entanglements and dynamics of polymer nanocomposites containing spherical nanoparticles

We investigate the effect of nanoparticles on polymer structure, nanoparticle dynamics and topological constraints (entanglements) in polymer melts for nanoparticle loading above percolation threshold as high as 40.9% using stochastic molecular dynamics (MD) simulations. An increase in the number of entanglements (decrease of Ne with 40.9% volume fraction of nanoparticles dispersed in the polymer matrix) in the nanocomposites is observed as evidenced by larger contour lengths of the primitive paths. Attraction between polymers and nanoparticles affects the entanglements in the nanocomposites and alters the primitive path. The diffusivity of small sized nanoparticles deviates significantly from the Stokes- Einstein relation.

Miscibility and nanoparticle diffusion in ionic nanocomposites

We investigate the effect of various spherical nanoparticles in a polymer matrix on dispersion, chain dimensions and entanglements for ionic nanocomposites at dilute and high nanoparticle loading by means of molecular dynamics simulations. The nanoparticle dispersion can be achieved in oligomer matrices due to the presence of electrostatic interactions. We show that the overall configuration of ionic oligomer chains, as characterized by their radii of gyration, can be perturbed at dilute nanoparticle loading by the presence of charged nanoparticles. In addition, the nanoparticle’s diffusivity is reduced due to the electrostatic interactions, in comparison to conventional nanocomposites where the electrostatic interaction is absent. The charged nanoparticles are found to move by a hopping mechanism.