High-Frequency Dielectric Relaxation in Trehalose-Glycerol Mixtures
O. Anopchenko, J. Obrzut, B. W. Rust *
Polymers Division, MSEL
* Mathematical and Computational Sciences Division, ITL
National Institute of Standards and Technology, Gaithersburg, MD 20899
Broadband dielectric measurements were performed on a series of trehalose-glycerol mixtures in a wide concentration range of glycerol and temperature swept from 220 K to 350 K. Relaxation spectra were obtained directly from the measured dielectric spectra by means of a regularization technique. A relaxation map for a high frequency dielectric relaxation in the mixture is obtained. It is found that glycerol slows down the high frequency relaxation in trehalose. The effect is more pronounced at low temperatures. A composition diagram of the slowing down effect is presented. An activation energy and entropy of the high frequency relaxation of the mixture are increasing with glycerol concentration. An excess permittivity of the mixture demonstrates a transition from antiparallel to parallel alignment of molecular dipole moments. The transition occurs at a composition that corresponds to 2 glycerol molecules to 1 trehalose molecule. Our findings suggest that at the concentration of glycerol above this threshold glycerol-rich dynamic domains are being formed in the mixture. This study is aimed at mechanisms of high frequency dielectric relaxation in organic hybrid materials which are of interest to electronics and nano technology. The results are also helpful in getting an insight into the increased anhydrous preservation of proteins.
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