Comment on “Study of dielectric relaxations of anhydrous trehalose and maltose glasses” [J. Chem. Phys. 134, 014508 (2011)]

Kamiński, Kamil; Włodarczyk, P.; Paluch, Marian

doi:10.1063/1.3647898

Cited by 3 publications

(11 citation statements)

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“…It can be seen that the imaginary and the real components of the complex permittivity cross at some frequency f c which coincides perfectly with the maximum of loss of the relaxation process, labeled by Bhardwaj et al as the structural one. One can add that a similar situation was observed in the case of data presented by Kwon et al…”

Section: Resultssupporting

confidence: 86%

Dielectric Studies on Molecular Dynamics of Two Important Disaccharides: Sucrose and Trehalose

et al. 2012

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Broadband dielectric measurements were carried out in the supercooled as well as in the glassy state of two very important disaccharides: trehalose and sucrose. Multiple relaxation processes were observed. Above the glass transition temperatures of examined disaccharides structural relaxation of cooperative origin was detected, where in the glassy state more local motions (secondary modes) appeared. Our data were discussed in light of the findings reported by other groups. We pointed out that sample preparation might impact mobility and, thus, dielectric loss spectra in a significant way. Consequently, it may lead to misinterpretation of the dielectric relaxation processes. Moreover, impact of physical aging and pressure on dynamics of two secondary relaxation processes observed in the glassy state of trehalose and sucrose has been investigated. Additionally, we have demonstrated that, in contrast to the calorimetric measurements (DSC), activation energies of the β- and γ-relaxation processes observed in the glassy state of sucrose and trehalose do not change as a result of physical aging. Finally, we found out that the β-relaxation process slows down as pressure increases. We interpreted this fact in view of increasing rigidity of the structures of disaccharides.

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Section: Resultssupporting

confidence: 86%

Dielectric Studies on Molecular Dynamics of Two Important Disaccharides: Sucrose and Trehalose

et al. 2012

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“…Changes in temperature (T), pressure, chemical structure and purity have been studied by BDS by several authors revealing a strong impact of all four on the emerging dynamics. [23][24][25][26][27][28][29][30][31] Using FTIR Imamura et al 32 and Wolkers et al 33,34 found a remarkable sensitivity to the glass transition of the spectral positions of hydroxyl group vibrations. In the following we present the temperature dependence of fucose in a wide range around the glass transition temperature, T g , and time dependent (aging) measurements for T o T g .…”

Section: Introductionmentioning

confidence: 99%

Glassy dynamics and physical aging in fucose saccharides as studied by infrared- and broadband dielectric spectroscopy

Kossack

Adrjanowicz

Tarnacka

et al. 2013

Phys. Chem. Chem. Phys.

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Fourier Transform Infra Red (FTIR) and Broadband Dielectric Spectroscopy (BDS) are combined to study both the intra- and inter-molecular dynamics of two isomers of glass forming fucose, far below and above the calorimetric glass transition temperature, T(g). It is shown that the various IR-active vibrations exhibit in their spectral position and oscillator strength quite different temperature dependencies, proving their specific signature in the course of densification and glass formation. The coupling between intra- and inter molecular dynamics is exemplified by distinct changes in IR active ring vibrations far above the calorimetric glass transition temperature at about 1.16T(g), where the dynamic glass transition (α relaxation) and the secondary β relaxation merge. For physically annealed samples it is demonstrated that upon aging the different moieties show characteristic features as well, proving the necessity of atomistic descriptions beyond coarse-grained models.

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“…Comparing the relaxation times at 143 °C, they are 5.88 × 10 –6 s (De Gusseme) and 4.49 × 10 –7 s (Kaminski). These differences were difficult to observe in the earlier publication since the temperature scale was compressed to accommodate numerous relaxation profiles in one figure (Figure 1 in the paper by Kaminski et al). There are similar differences in the relaxation values reported by different groups for the two local relaxations as well (Figure 1 in the paper by Kaminski et al).…”

Section: Resultsmentioning

confidence: 81%

“…Recently, Kwon et al recognized the shoulder in the conductivity tail to be the α-relaxation peak and modeled it without dc conductivity removal . Kaminski et al argued that the relaxation peak, which Kwon et al labeled as the α-relaxation, originated from dc conductivity and the actual primary relaxation was mislabeled as the excess wing . However, in an effort to perform a careful comparison, we digitized the relevant plots from the literature and present all the data in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…However, since the contribution of dc conductivity is significant in the lower frequency range where the α-relaxation and excess wing appear, modeling the data without conductivity removal has the potential to lead to erroneous results. Kaminski et al argued that the peak designated as primary relaxation by Kwon et al is due to dc conductivity and the excess wing observed by Kwon et al is the structural relaxation . Thus, there is still lack of consensus regarding the exact nature of the different dielectric relaxations in amorphous trehalose.…”

Section: Introductionmentioning

confidence: 99%

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Use of Dielectric Spectroscopy To Monitor Molecular Mobility in Glassy and Supercooled Trehalose

Bhardwaj

Suryanarayanan

2012

J. Phys. Chem. B

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Dielectric spectroscopy was used to comprehensively characterize the molecular mobility in amorphous trehalose, an extensively used bioprotective agent. Isothermal frequency sweeps were carried out at different temperatures in the glassy and supercooled liquid states of freeze-dried trehalose. Two previously reported secondary relaxations were observed at temperatures far below its glass transition temperature (T(g)). At temperatures close to T(g), removal of dc conductivity contribution revealed a relaxation peak. The origin of this peak was evaluated using several diagnostic tests and determined to be the α-relaxation. There was also an excess wing in the high-frequency tail of α-relaxation. Sub-T(g) annealing caused the primary relaxation to shift to lower frequencies, enabling resolution of the excess wing, which was characterized to be the true Johari-Goldstein (JG) relaxation. A qualitatively similar effect of annealing on JG relaxation was also observed. The average relaxation times of the two previously reported secondary relaxations were unaffected by annealing.

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Comment on “Study of dielectric relaxations of anhydrous trehalose and maltose glasses” [J. Chem. Phys. 134, 014508 (2011)]

Abstract: Dynamics of glass-forming liquids. III. Comparing the dielectric α-and β-relaxation of 1-propanol and -terphenyl

Cited by 3 publications

References 10 publications

Dielectric Studies on Molecular Dynamics of Two Important Disaccharides: Sucrose and Trehalose

Dielectric Studies on Molecular Dynamics of Two Important Disaccharides: Sucrose and Trehalose

Glassy dynamics and physical aging in fucose saccharides as studied by infrared- and broadband dielectric spectroscopy

Use of Dielectric Spectroscopy To Monitor Molecular Mobility in Glassy and Supercooled Trehalose

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