Dramatic slowing down of the conformational equilibrium in the silyl derivative of glucose in the vicinity of the glass transition temperature

The vitrification process is usually preceded by a significant change (around 6-8 decades) in the viscosity, structural relaxation times, or diffusion that occurs in a relatively small range of temperatures in fragile liquids. Along with this phenomenon, conformations of the molecules vary as well....

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Bibliographic Details
Published in:Soft matter 2019, Vol.15 (37), p.7429-7437
Main Authors: Wolnica, K, Dulski, M, Kami ska, E, Tarnacka, M, Wrzalik, R, Zi ba, A, Kasprzycka, A, Nowak, M, Jurkiewicz, K, Szeja, W, Kami ski, K, Paluch, M
Format: Article
Language:English
Subjects:
Atomic properties
Carbohydrates
Distribution functions
Glass transition temperature
Molecular weight
NMR
Nuclear magnetic resonance
Polymers
Relaxation time
Temperature
Thin films
Transition temperatures
Viscosity
Vitrification
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Summary:The vitrification process is usually preceded by a significant change (around 6-8 decades) in the viscosity, structural relaxation times, or diffusion that occurs in a relatively small range of temperatures in fragile liquids. Along with this phenomenon, conformations of the molecules vary as well. In fact, this process is studied in bulk polymers and high molecular weight materials deposited in the form of thin films. On the other hand, spatial rearrangement of small glass formers in the supercooled liquid state has not been intensively investigated, so far. Herein, data obtained from measurements carried out using various experimental techniques on supercooled 1,2,3,4,6-penta- O -(trimethylsilyl)- d -glucopyranose (S-GLU) have revealed that rotations of silyl moieties along with the deformation in the saccharide ring are significantly slowed down in the vicinity of the glass transition temperature ( T g ). These intramolecular reorganizations affect the structural relaxation time, atomic pair distribution function, integrated intensity, as well as a number of bands and signals observed, respectively, in the Raman and NMR spectra. Data reported herein offer a better understanding of the conformational variation and time scale of this process in the complex and flexible molecules around the T g . This paper reports significantly slowed down of the rotations of silyl moieties along with the deformation in the saccharide ring in 1,2,3,4,6-penta- O -(trimethylsilyl)- d -glucopyranose (S-GLU) in the vicinity of the glass transition temperature.
ISSN:1744-683X
1744-6848
DOI:10.1039/c9sm01259a