Molecular dynamics simulations on dextran hydrogels

To probe the detailed structure of dextran hydrogels, periodical models for three dextran hydrogel systems with different dextran contents have been constructed and compared using molecular dynamic simulations. The software packages of Amorphous and Discover in Material Studio with COMPASS force field were used for the simulation. Energy minimization and geometry optimization were used to refine the models. In particular, the structure and dynamic movement of dextran chains which impose on water in the dextran hydrogel systems have been studied. The results show that in the physically crosslinked dextran hydrogels, KCl served as the crosslinker and it interacted with dextran via the oxygen atoms of hydroxyl groups in dextran ring. With increasing dextran content, the free volumes of the hydrogels and the diffusion coefficients of water in the hydrogel decrease. By the radial distribution analysis, the water in the hydrogel networks was found to interact with dextran via hydrogen bond and there are at least three kinds of water in the physically crosslinked dextran hydrogels. These results have a great significance for understanding the structure and properties of the hydrogel.