Effect of Moisture Content on Glass Transition Temperature and Diffusion Properties of Low-molecular-weight Sugars by Molecular Dynamics Simulation
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Abstract:
In this study, the effect of different moisture contents on glass transition temperature (Tg) and diffusion properties of low-molecular-weight sugars (such as sucrose and trehalose) were evaluated, using the COMPASS force field and isothermal-isobaric (NPT) ensemble. Molecular dynamics simulation was used to obtain the glass transition temperatures of sugars by simulating a plot of the specific volume of low-molecular-weight sugar in a temperature range of 180 K to 460 K versus the corresponding temperature. At 298 K, the mean square displacement (MSD) of water molecules in the sugar systems with varying moisture content was simulated, and the effect of moisture content on the diffusion properties was analyzed. In addition, when the temperature was 298K and the moisture content was 5%, the radial distribution function (RDF) of oxygen atoms in water and in the low-molecular-weight sugar system was studied. The results indicated that the value of Tg and the ability to form hydrogen bonds with water molecules were higher for trehalose than for sucrose at the same moisture content. With increasing moisture content, the value of Tg in the two sugar models showed a significant downward trend, water molecules more easily diffused into the sugar systems, and the chance to interact with sugar molecules increased.
