2018-06-06
10:15 at HCP F 43.4

Modeling of dense polymer melts near spherical and anisotropic nanoparticles

Argyrios Karatrantos

Luxembourg Institute of Science and Technology, Luxembourg

The addition of nanoparticles (nanospheres, nanotubes, nanoplatelets) to a polymer melt can result in materials with significantly improved properties. Understanding the polymer structure and dynamics near nanoparticles is important when designing fabrication methods for nanocomposites [1]. The effect of bare spherical nanoparticles on polymer structure and dimensions was investigated by means of molecular simulations. It has been shown unambiguously that polymer chains are not disturbed by the presence of repulsive nanoparticles. In contrast, even short polymer chains can be perturbed by the presence of attractive nanoparticles when the polymer radius of gyration is larger than the nanoparticle radius [2]. The diffusivity of nanoparticles with radius smaller than the tube diameter does not follow the Stokes – Einstein formula [3]. Moreover, the primitive path can be determined, by using topological algorithms [4], and was observed a decrease in the number of entanglements with the addition of nanoparticles. Furthermore, a family of new nanocomposites (ionic), in which nanoparticles with ionic functionalities react with a polymer with a functionality of the opposite charge, is investigated. The presence of oppositely charged ions at the polymer/nanofiller interphase can promote dispersion, which is always a major challenge in conventional polymer nanocomposites where the ionic interactions are absent [5]. There is a strong research interest in nanocomposites with anisotropic cylindrical nanoparticles, such as single wall carbon nanotubes (SWCNT). The polymer tracer diffusivity in SWCNT / polymer nanocomposites is suppressed at low SWCNT concentrations (<0.4%) to a surprising extent [6]. The structure and dynamics of SWCNT / polymer nanocomposites was investigated by means of molecular dynamics. It was found that polymers follow unperturbed Gaussian statistics in the vicinity of the SWCNT for polymer radius of gyration greater than the SWCNT radius in dilute nanoparticle loading. Moreover, there was a large heterogeneity in the polymer dynamics due to the adsorbed polymers along the SWCNT surface [7]. In addition, dissipative particle dynamics simulations were performed in order to investigate the polymer structure and entanglements up to the percolation threshold [8].

[1] C. C. Lin, E. Parrish, R.J. Composto; Macromolecules; 2016, 49, 5755.
[2] A. Karatrantos, N. Clarke, M. Kroger; Polymer Reviews, 2016, 56, 385.
[3] A. Karatrantos, N. Clarke, R.J. Composto, K. I. Winey; J. Chemical Physics, 2017, 146, 203331.
[4] R. S. Hoy, K. Foteinopoulou, and M. Kroger; Phys. Rev. E. 2009, 80, 031803.
[5] A.Karatrantos, Y. Koutsawa, P. Dubois, N. Clarke, and M. Kroger; İn preparation, 2018.
[6] M. Mu, N. Clarke, R.J. Composto, K.I. Winey; Macromolecules, 2009, 42, 7091.
[7] A. Karatrantos, R. J. Composto, K. I. Winey, M. Kroger, and N. Clarke. Macromolecules, 2012, 45, 7274.
[8] A. Karatrantos, N. Clarke, R.J. Composto, K. I. Winey; Soft Matter, 2013, 9, 3877.