Heterogeneity of the state and functionality of water molecules sorbed in an amorphous sugar matrix

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Amorphous materials, comprised of sugar molecules, exhibit high hygroscopicity and the sorbed water exerts a major influence on physical stabilities of the matrix. To date, the water sorption behavior of amorphous sugars has been extensively investigated. However, most studies of the behavior of water, when sorbed to an amorphous sugar matrix, have implicitly assumed that all of the sorbed water molecules are in a single state: It is naturally expected that the random allocation and configuration of sugar molecules would result in heterogeneity of states for the sorbed water. Recently, we demonstrated the heterogeneity of state and functionality of water sorbed in amorphous sugar matrices by combining a Fourier transform IR spectroscopy and Fourier self-deconvolution technique; The sorbed water molecules were classified into five states, and the three of them mainly served to lower the glass transition temperature of an amorphous sugar matrix while the other two are independent.