ИСТИНА

One way to increase the affinity of epoxy matrices to carbon fibers consists in creating oxidative defects on the surface of the latter by treating it with oxidizing agents. However, experimental study of the structural organization of the epoxy binder and the interface between it and carbon fiber is complicated by the lack of long-range order in such systems. However, molecular dynamics modeling methods make it possible to study the structure and resulting properties of such composite materials [1]. We investigated the interaction between one common matrix, triethylenetetramine-cured epoxy resin ED-20, and graphene sheets containing oxidative defects (Figure 1A). We simulated four systems using molecular dynamics methods: with normal graphene (GP) and with graphene bearing hydroxyl (GP/OH), carbonyl (GP/2O) and carboxyl (GP/COOH) groups. The epoxy resin was cured in their presence in the same way as in [1] so that the epoxy resin formed one large aggregate. The epoxy matrix densifies near the surfaces of the graphene sheets, forming a mesophase enriched in bisphenol A and epichlorohydrin residues (Fig. 1B), due to the fact that they are able to form π-stacking interactions with graphene. It is worth noting that the presence of an oxidative defect increased the density of the hydrogen bond network inside the epoxy matrix. The dependences of the free energy of the systems on the gap between the graphene sheet and the surface of the ED-20 resin were calculated by the metadynamics method (Fig. 1C). Introduction of an oxidative defect of any kind more than doubles the free energy of graphene sheet detachment—that is, the affinity for the epoxy matrix, with hydroxylation being the largest (Figure 1D). We believe, that the nature of this phenomenon is that the introduction of even a point defect on the surface of a graphene sheet leads to the propagation of the electron density disturbance over a significant area, increasing its ability to undergo polar interactions with the matrix. This research was funded by the Ministry of Science and Higher Education of the Russian Federation (grant FENU 2024-0003).