ReaxFF Reactive Force Field Study of Polymerization of a Polymer Matrix in a Carbon Nanotube-Composite System

Abstract

Human transport to Mars and deep space explorations demand the development of new materials with extraordinary high performance-to-mass ratios. Promising candidates to fulfill these requirements are ultra-high strength lightweight (UHSL) materials, which consist of polymer matrices fortified by pristine carbon nanotubes (CNTs). Previous investigations have showed that with an increase in CNT diameter, its preferred configuration changes from a circular form to a flattened shape that can be obtained in high pressure or tension conditions. The ReaxFF reactive force field can reveal detailed chemical interactions at the atomistic scale. To enable ReaxFF simulations on CNT/polymer interfaces, we trained force field parameters to capture the proper structure of flattened carbon nanotubes (flCNTs), i.e. dumbbell-like shape CNTs, against available polymer consistent force fieldinterface force field (PCFF-IFF) data which had good proximity to density functional theory (DFT) data. In this study we used accelerated ReaxFF molecular dynamics simulation using the optimized force field to study the polymerization of diglycidyl ether of bisphenol F (Bis F) and diethyltoluenediamine (DEDTA) molecules in vicinity of circular and flattened carbon nanotubes. Our results indicate that the flat regions of flCNT are more favorable spots for the polymers to settle compared to curved regions due to higher binding energies. Moreover, higher dimer generation around flCNT results in more effective coating of the nanotube which leads to higher load transfer in compared to circular CNT. According to our results there is a high alignment between polymers and nanotube surface which is due to strong π-π interactions of aromatic carbon rings in the polymers and nanotubes. These atomistic ReaxFF simulations indicate the capability of this method to simultaneously observe the polymerization of monomers along with their interactions with CNTs.

Wetting Simulations of High-Performance Polymer Resins on Carbon Surfaces as a Function of Temperature Using Molecular Dynamics

“…A lattice constant of 2.46 Å was used with the primitive lattice vectors given by Gray et al [ 26 ]. Virtual pi electrons were modeled using dummy atoms to capture the effect of the pi electrons on aromatic carbon [ 8 , 27 ]. A detailed discussion about these virtual pi electrons can be found elsewhere [ 28 ].…”

Molecular Alignment of a Meta-Aramid on Carbon Nanotubes by In-Situ Interfacial Polymerization.

“…Here the angle brackets stand for the average value over all angles, and We use a ReaxFF reactive force field framework 24 with chemical acceleration tools to enable reaction barrier sampling at time-scales accessible to ReaxFF-based molecular dynamics [25][26][27][28][29] .…”

Comparative Study of Carbon Force Fields for the Simulation of Carbon Onions

“…Recently, a reparametrization version of the ReaxFF force field [52] was developed (ReaxFF-20). [53] The force field parameters were optimized to adequately capture the flattened carbon nanotube structure and the corresponding energy values. Its parameters were trained against the PCFF-IFF force field data, which shows good agreement with DFT-D2 data.…”