Structural order of water molecules around polyrotaxane including PEG, alpha-cyclodextrin, and alpha-lipoic acid linker on gold surface by molecular dynamics simulations

TMN Le and L Van Sang and H Washizu, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 24, 2176-2184 (2022).

DOI: 10.1039/d1cp04487g

In materials science, water plays an important part, especially at the molecular level. It shows various properties when sorbed onto surfaces of polymers. The structure of the molecular water ensemble in the vicinity of the polymers is under discussion. In this study, we used molecular dynamics methods to analyze the structure of water in the vicinity of the polymer polyrotaxane (PR), composed of alpha- cyclodextrins (alpha-CDs), a poly(ethylene glycol) (PEG) axial chain, and alpha-lipoic acid linkers, at various temperatures. The distribution of water around the functional groups, hydrogen bond network, and tetrahedral order were analyzed to classify the various types of water around the polymer. We found that the tetrahedral order of water had a strained relationship from the XES experiment. Four water regions were separated from each other in the vicinity of 1 to 5 angstrom around PR. The intermediate and non-freezing water were formed due to the interaction between water molecules and the functional groups, such as hydroxyl, ether, and ester.

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