title: Predict the glass transition temperature and plasticization of β-cyclodextrin/water binary system by molecular dynamics simulation.
abstract: The glass transition temperature, diffusion behavior and plasticization of β-cyclodextrin (β-CD), and three amorphous β-CD/water mixtures (3%, 5% and 10% [w/w] water, respectively) were investigated by molecular dynamics simulation, which were performed using Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) force field and isothermal-isobaric ensembles. The specific volumes of four amorphous cells were obtained as a function of temperature. The glass transition temperatures (T(g)) were estimated to be 334.25 K, 325.12 K, 317.32 K, and 305.41 K for amorphous β-CD containing 0%, 3%, 5% and 10% w/w water, respectively, which compares well with the values observed in published literature. The radial distribution function was computed to elucidate the intermolecular interactions between amorphous β-CD and water, which acts as a plasticizer. These results indicate that the hydrogen bond interactions of oxygen in hydroxyl ions was higher than oxygen in acetal groups in β-CD amorphous mixtures with that in water, due to less accessibility of ring oxygens to the surrounding water molecules. The mobility of water molecules was investigated over various temperature ranges, including the rubbery and glassy phases of the β-CD/water mixtures, by calculating the diffusion coefficients and the fractional free volume. In β-CD amorphous models, the higher mobility of water molecules was observed at temperatures above Tg, and almost no change was observed at temperatures below T(g).
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China.
authors.forename: Guohui
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Center for High Performance Computing, Northwestern Polytechnical University, Xi'an 710071, Shanxi, China.
authors.forename: Tianhai
authors.initials: T
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China. Electronic address: wanjiencu@aliyun.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Wan
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China.
authors.forename: Chengmei
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China.
authors.forename: Risi
authors.initials: R
authors.lastname: Wang
mesh_terms: D002236:Carbohydrate Conformation; D004058:Diffusion; D005898:Glass / Q000737:chemistry*; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D010969:Plastics / Q000737:chemistry*; D044366:Transition Temperature; D014867:Water / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D010969:Plastics; D047392:beta-Cyclodextrins; D014867:Water; C031215:betadex
keywords: Glass transition; Molecular dynamics simulation; Plasticization; β-Cyclodextrin