Atomistic Scale Analysis of the Carbonization Process for C/H/O/N-Based Polymers with the ReaxFF Reactive Force Field

Abstract

During the carbonization process of raw polymer precursors, graphitic structures can evolve. The presence of these graphitic structures affects mechanical properties of the carbonized carbon fibers. To gain a better understanding of the chemistry behind the evolution of these structures, we performed atomistic scale simulations using the ReaxFF reactive force field. Three different polymers were considered as a precursor: idealized ladder PAN (polyacrylonitrile), a proposed oxidized PAN and PBO (poly(p-phenylene-2,6-benzobisoxazole)). We determined the underlying molecular details of polymers conversion into a carbon fiber structure. Since these are C/H/O/N-based polymers, we first developed an improved force field for C/H/O/N chemistry based on the Density Functional Theory (DFT) data with a particular focus on N2 formation kinetics and its interactions with polymer-associated radicals formed during the carbonization process. Then, using this improved force field, we performed atomistic scale simulations of the initial stage of the carbonization process for the considered polymers. Based on our simulation data we determined the molecular pathways for the formation of low-molecular weight gas-species, all-carbon rings crucial for further graphitic structures evolution and possible alignment of the evolved all-carbon 6-membered rings clusters.

Molecular dynamics simulation of reversible electroporation with Martini force field

“…Since the electric field E ion is also much higher than E ext , the influence of the external electric field can be even neglected.As this work is based on coarse-grained (not atomistically detailed) force field, it is preferred to analyze or understand the results in a qualitative or semiquantitative way rather than comparing specific values with other results. Nevertheless, results including pore formation time and pore size are even comparable with previous simulations [8–11] which adopted different models and initial conditions.In this investigation, the simulation of reversible electroporation mechanism was performed with a non-reactive Martini force field, but in reality, the system involves chemical reactions [14–16] that cannot be simulated using this force field. In order to achieve this, a more accurate model is needed, including: (a) adopting all-atom force field directly with reactive force field.…”

“…In this investigation, the simulation of reversible electroporation mechanism was performed with a non-reactive Martini force field, but in reality, the system involves chemical reactions [14–16] that cannot be simulated using this force field. In order to achieve this, a more accurate model is needed, including: (a) adopting all-atom force field directly with reactive force field.…”

Graphene reinforced carbon fibers

“…Moreover, the force field is extended to C/H/O/N atoms widening its application to alternative polymer precursors such as stable oxidized PAN and PBO (poly(p-phenylene-2,6-benzobioxazole)). For a detailed description of this force field development process, see our previous published work (51).…”

Computational study of the effect of core–skin structure on the mechanical properties of carbon nanofibers

“…The mechanical properties of CNFs with and without the graphitic skin layer are investigated in this study using large-scale molecular dynamics (MD) simulations. This computational technique has been successfully applied to analysis of chemical reactions leading to the formation of carbon fiber microstructure from molecular precursors [25][26][27][28][29][30][31][32], oxidation of carbon fibers [33], as well as the elementary processes involved in mechanical deformation of carbon fibers [27,28,[34][35][36][37]. The high computational cost of MD simulations, however, prevents application of this technique for direct evaluation of the mechanical properties of fibers with heterogeneous microstructure, such as the ones of core-skin carbon fibers.…”