Quantum chemical investigation of the influence of the presence of a graphen-cluster on the energy of covalent bonds on the polyamid fragment in nanocomposite

The energy values have been calculated by the density functional theory with the exchange-correlation functional B3LYP, the basic set 6-31G(d,p) and Grimme dispersion corrections of covalent bonds in a free molecule of dioligomer e−aminocaproic acid (ACA) and when it is part of an intermolecular complex with a graphene plane. The calculations has been performed to determine the effect of the presence of carbon fillers on the stability of thermoplastic polymers to which ACA oligomers belong, because it is known that the bonding energy in the polymer matrix correlates with the tear energy of the corresponding nanocomposite. As a fragment of the polyamide, ACA dioligomer was used, which is formed by the condensation of two ACA molecules, and for the graphene plane poliaromatic molecule with gross composition C48H18 was selected, which is commensurate with the dimer of the considered amide. The energy of the covalent bond was calculated based on the fact that this value is numerically identical to the energy effect of the reaction of its homolytic rupture with the formation of two radicals in the doublet state. An analysis of the results of quantum chemical studies shows that the bond between nitrogen and carbon atoms (−HN−CO−), in the amide group of the free molecule of the ACA dioligomer, is the strongest and its energy is 447.1 kJ/mol. In the formed nanocomposite of polyamide – fragment of the graphene plane, the energy of all the covalent bonds studied is significantly increased compared to the free molecule of the ACA dioligomer. This indicates a possible increase in the thermal stability of this nanocomposite, which correlates with the experimental data.