Molecular dynamics simulation of calcium silicate hydrate/tannic acid interfacial interactions at different temperatures: configuration, structure and dynamic

In the paper, the effect of temperature on tannic acid molecular conformation and the interaction between tannic acid and substrate were investigated systematically by molecular dynamics. The tensile force of tannin acid separation from CSH matrix at three temperatures was calculated by SMD simulation, and then the adhesion energy between tannin acid and CSH was calculated by Bell Model. The results showed that high temperature affects the gyration of the single bond in the tannic acid, which leads to the increase of tannic acid molecular chain size and radius of gyration. Tannic acid molecules are more extended and the contact area with the substrate became larger in high temperature, which enhanced interfacial adhesion energy. Further, by analyzing the structure and dynamics of the composite, it comes out that not only the substrate has more sites available for tannic acid but also the interfacial ionic bonding formed is more stable after high temperature. Enhanced interfacial chemical bonds limit the bending motion of tannic acid molecular, which leave them in a well-stretched state, to causes tannic acid to be stably adsorbed on the substrate.