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A study on the progress of mutarotation above and below the Tg and the relationship between constant rates and structural relaxation times.
- Source :
- Physical Chemistry Chemical Physics (PCCP); 8/21/2017, Vol. 19 Issue 31, p20949-20958, 10p
- Publication Year :
- 2017
-
Abstract
- Comprehensive FTIR studies on the progress of mutarotation in d-fructose mixed with maltitol have been carried out over a wide range of temperatures, both above and below the glass transition temperature T<subscript>g</subscript>. In addition to the analysis of single bands, we have developed a completely new approach considering the full spectral range to follow the overall progress of the reaction. We have found that at the calorimetric T<subscript>g</subscript>, there is a clear change in the temperature dependence of constant rates. The activation barrier for mutarotation changes from around 59 kJ mol<superscript>−1</superscript> (the supercooled state) to around 249 kJ mol<superscript>−1</superscript> (the glassy state). This dramatic variation in the activation barrier is consistent with the change in the mechanism of this specific chemical conversion, as theoretically considered by Wlodarczyk et al. [Phys. Chem. Chem. Phys., 2014, 16, 4694–4698]. Alternatively, it can also be connected to the change in the viscosity of the sample. Additionally, we investigated the relationship between constant rates (k) of mutarotation, structural relaxation times (τ<subscript>α</subscript>), and dc conductivity (σ<subscript>dc</subscript>) above and below the glass transition temperature. It was found that there was a linear correlation between all these quantities; they scale with various exponents changing at T<subscript>g</subscript>. Our results also indicate that a single activation barrier might not be sufficient to describe the mutarotation process. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 14639076
- Volume :
- 19
- Issue :
- 31
- Database :
- Complementary Index
- Journal :
- Physical Chemistry Chemical Physics (PCCP)
- Publication Type :
- Academic Journal
- Accession number :
- 124554296
- Full Text :
- https://doi.org/10.1039/c7cp02046e