Molecular Mobility in Supercooled Trehalose

Abstract

The molecular mobility of amorphous anhydrous trehalose (C12H22O11) was investigated by means of temperature-modulated differential scanning calorimetry (TMDSC) and dielectric analysis (DEA). TMDSC was used to perform a specific heat spectroscopy, which appeared essential, as dielectric measurements above T g were hampered by dc conductivity. TMDSC and DEA are useful complementary techniques for the study of the molecular mobility of this important bioprotecting agent. The study of the primary relaxation of trehalose, above the glass transition temperature, yielded the determination of the fragility index m and the stretching exponent β. Τhe correlation between m and β was also discussed. Dielectric studies of the sub-T g domain highlighted two distinct secondary relaxation processes, whose dynamical features were evaluated.

Ideally glassy hydrogen-bonded networks

“…The glass transition temperatures T g of a few polyalcohols and sugars are listed in Table I, together with the extrapolated slopes of reduced viscosity (fragilities m) on reduced temperature scale, that is, m = dlog τ/dlog(T g /T) T = Tg [14]. Saccharide data [15,16] are also included, as these also have strong H-bonding interactions.…”

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

“…However, one should emphasis that the opposite pattern of behavior is usually observed. It is worth mentioning that trehalose and maltose were also previously investigated by Kaminski et al 3 and De Gusseme et al 4 All these authors found that the structural relaxation peak in dielectric spectra of the mentioned disaccharides can be visible only at very high temperatures (much above Tg) in a very high frequency region. It was shown that upon lowering temperature the dc conductivity begins to obscure structural relaxation process.…”

“…At this place, it should be also explained why this process was visible in loss spectra of trehalose and maltose shown by Kwon et al, 1 while it is absent in dielectric spectra reported by Kaminski et al 2 and De Gusseme et al 4 To address this question, we would like to refer the readers to papers by Paluch et al 7 and Richert 9, 10 who showed that the Debye-like process can be generated in loss spectra as a result of using blocking electrode technique. As discussed in Refs.…”

“…4 by Kaminski et al 2 and that obtained by Kwon et al 1 and constructed the relaxation map, as shown in Fig. 1.…”

Prediction of the Onset of Crystallization of Amorphous Sucrose Below the Calorimetric Glass Transition Temperature from Correlations with Mobility

“…A similar trend for the temperature dependence of b was previously obtained for other compounds, where beta was found to increase to a value close to unity, indicating homogenously relaxing system at temperatures much higher than the glass transition temperature. 13,14 Recently DeGusseme et al 15 observed temperature dependence of the nonexponentiality parameter for a secondary relaxation process observed in supercooled trehalose. In their study, the authors observed two secondary relaxation processes, where the nonexponentiality parameter showed distinct temperature dependence for one such process.…”