Molecular Dynamics Study on Interfacial Strengthening Mechanisms of Ettringite/Polymer Nanocomposites

Compared with polymer-modified ordinary-Portland-cement-based materials, research on cement materials based on polymer-modified sulfoaluminate is still in the preliminary stage and lacks an understanding of the mechanism of the interaction interface. The aim of this work is to study the bond performance of ettringite, the main hydration product of sulfoaluminate cement, with various types of polymers using molecular dynamics methods. Steered molecular dynamics were used to simulate the separation of polyamide (PA), polyethylene glycol (PEG), polyacrylic acid (PAA) and polypropylene (PP) from ettringite substrate, reflecting the order of bond properties of the four polymers: PAA > PA > PEG > PP. The internal mechanism of bond properties between different polymers and ettringite was analyzed by studying the local structure and dynamic characteristics. The results show that a Ca–O ionic pair is formed between the calcium ions on the surface of the polymer and ettringite substrate, resulting in strong interaction. In addition, the formation of a H bond also contributes to bond performance. The properties of the polymer itself, such as the degree of polymerization and branched-chain freedom, affect the coordination of the polymer to the substrate. This study provides valuable insights for advancing the development of polymer-modified sulfoaluminate-cement-based materials.

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