Atomistic investigation of a carbonization process for C/H/O/N-based polymers with use of the reactive potentials: ReaxFF*

During a carbonization process of the raw polymer precursors, the graphitic structures evolve and are responsible for improved mechanical properties of the carbonized carbon fibers. To gain a deeper understanding of a chemistry behind an evolution of these graphitic structures, we perform atomistic simulations using a reactive force field: ReaxFF. We considered three different polymers as a precursor: idealized ladder PAN, proposed oxidized PAN and PBO to understand how underlying molecular details of polymers direct final carbon fibers structure. Since these are C/H/O/N-based polymers, firstly we proposed an improved force field for C/N/H chemistry based on new DFT data. Then, with use of this improved force field, we perform atomistic simulations of the carbonization process for the considered polymers. Based on these simulations we were able to determine small molecules, as well, all carbon rings productions, and analyzed the graphitic structures evolutions. We also performed the stress-strain simulations on the initially carbonized samples and were able to assess how a presence of the graphitic structure affects the mechanical responds.