Theoretical study on the interaction of polychlorotrifluoroethylene fragments with graphene-like planes

Abstract

The interaction of graphene with fragments of polychlorotrifluoroethylene (PCTFE) has been studied by quantum chemistry methods. Within the frameworks of the density functional theory with B3LYP exchange-correlation functional, 6-31G(d,p) basis set and the Grimme dispersion correction, and the second order Møller-Plesset perturbation theory (MP2), the values of the interaction energy of graphene with polychlorotrifluoroethylene oligomers were calculated and the most probable structures of their intermolecular complexes were optimized. As a graphene model, graphene-like planes (GLP) of different sizes were chosen, namely: С40Н16, С54Н18 and С96Н24. Oligomers of polychlorotrifluoroethylene and graphene-like planes in the formed nanocomposites are located closer to each other than individual polymer links. When comparing the results of calculations by the B3LYP-D3/6-31G(d,p) and MP2/6-31G(d,p) methods, both in the case of interactions of polychlorotrifluoroethylene oligomers with each other and intermolecular complexes of polychlorotrifluoroethylene oligomers and graphene-like planes, it has been found that the second order Møller-Plesset method is characterized by a larger intermolecular distance and a lower energy of intermolecular interactions compared to the method of the density functional theory with the Grimme dispersion correction, which is explained by the fact that the MP2 method does not fully take into account the relatively small components of dispersion interactions. Analysis of the calculation results using quantum chemistry methods shows that the addition of graphene-like planes to the polychlorotrifluoroethylene polymer leads to an increase in the intermolecular interaction energy, regardless of the calculation method used and the sizes of polychlorotrifluoroethylene oligomers and graphene-like planes. This may indicate greater strength and thermal stability of the nanocomposite based on graphene-like planes with polychlorotrifluoroethylene oligomers. The zero value of the Gibbs free energy ΔGreact for the interaction of two dimers with each other is characteristic at 270 K, and the similar value of the interaction of the PCTFE dimer with GLP is at a much higher temperature (420 K). This fact reflects the growth in thermostability of nanocomposites as compared to the polymer itself.