Calorimetric studies at low temperatures of glass‐forming 1‐butanol and 2‐butanol

Abstract

We present calorimetric experiments and specific‐heat Cp(T) measurements of 1‐butanol (n‐butanol) and of one of its chemical isomers, the secondary alcohol 2‐butanol (sec‐butanol), around its glass transition Tg as well as at low temperatures (1.6–30 K). We have obtained and measured both the glass and crystalline states of 1‐butanol, and the glass state of 2‐butanol which is an even better glass former. In this work, we focus on the comparative study of the calorimetric or thermodynamic properties of the glassy states of these two isomers of butanol, determining their glass‐transition temperatures, their discontinuities in specific heat at Tg, and the corresponding enthalpy fictive temperatures. At temperatures below 10 K, both isomers present the typical broad maximum for glasses in Cp/T3, often called the boson peak, its magnitude being much larger in 2‐butanol than in 1‐butanol.

Frustration of crystallisation by a liquid–crystal phase

“…The formation of the LC phase from the isotropic liquid is fully consistent with existing calorimetric measurements 8 14 15 28 . In particular, calorimetric measurements, starting from the n -butanol glass, using different heating speeds 15 show an exothermic peak corresponding to the “glacial phase” and a separate exothermic first-order transition into the stable crystal above 155 K. Thus, the “glacial phase” can now be reinterpreted as the slow formation of a rippled lamellar LC phase.…”

Unusual Solvent Effects on Optical Properties of Bi-Icosahedral Au25 Clusters

“…This temperature is often assigned to the dynamic crossover temperature. At the dynamic crossover temperature, solvent will attain higher density liquid status from low density liquid or, in other words, the shift from fragile to strong liquid. − Similar dynamic crossover temperatures were observed for water bound to proteins and DNA . The dynamic crossover phenomenon was also found in other solvents and alcohols. , …”

“…74 The dynamic crossover phenomenon was also found in other solvents 72 and alcohols. 71,75 Interestingly the plot of absorption maximum for higher energy peak vs temperature for bi-Au 25 is shown in Figure 6B, and no drastic shifts were observed unlike what was observed at low energy peaks. Note that the absorption at this energy region is dominated by the absorption of individual icosahedrons.…”

A systematic study of the isothermal crystallization of the mono-alcohol n-butanol monitored by dielectric spectroscopy

“…These two properties, a large dielectric signal and slow crystallization, makes n-butanol an ideal candidate for monitoring isothermal crystallization in real time by dielectric spectroscopy. Crystallization of n-butanol has previously been studied with x-ray diffraction [19,20], infrared spectroscopy [21,22], calorimetric methods [23], and phase contrast microscopy [24]. However, no systematic study of the temperature dependence and reproducibility of the crystallization kinetics has been reported.…”