Corresponding States of Structural Glass Formers

The variation with respect to temperature T of transport properties of 58 fragile structural glass forming liquids (68 data sets in total) are analyzed and shown to exhibit a remarkable degree of universality. In particular, super-Arrhenius behaviors of all super-cooled liquids appear to collapse to one parabola for which there is no singular behavior at any finite temperature. This behavior is bounded by an onset temperature To above which liquid transport has a much weaker temperature dependence. A similar collapse is also demonstrated, over the smaller available range, for existing numerical simulation data.Comment: 6 pages, 2 figures. Updated References, Table Values, Submitted for Publicatio

Molecular origin of enhanced proton conductivity in anhydrous ionic systems

YesIonic systems with enhanced proton conductivity are widely viewed as promising electrolytes in fuel cells and batteries. Nevertheless, a major challenge toward their commercial applications is determination of the factors controlling the fast proton hopping in anhydrous conditions. To address this issue, we have studied novel proton-conducting materials formed via a chemical reaction of lidocaine base with a series of acids characterized by a various number of proton-active sites. From ambient and high pressure experimental data, we have found that there are fundamental differences in the conducting properties of the examined salts. On the other hand, DFT calculations revealed that the internal proton hopping within the cation structure strongly affects the pathways of mobility of the charge carrier. These findings offer a fresh look on the Grotthuss-type mechanism in protic ionic glasses as well as provide new ideas for the design of anhydrous materials with exceptionally high proton conductivity

New insight into relaxation dynamics of an epoxy/hydroxy functionalized polybutadiene from dielectric and mechanical spectroscopy studies

Dielectric and mechanical spectroscopy methods have been employed to describe the temperature dependencies of the segmental and macromolecular relaxation rates in epoxy/hydroxy functionalized polybutadiene. Dielectric studies on the dynamics of segments of the polymer as well as the mobility of small ions trapped in the system have been carried out both as a function of temperature and pressure under isobaric and isothermal conditions, respectively

New experimental evidence about secondary processes in phenylphthalein-dimethylether and 1,1 '-bis(p-methoxyphenyl)cyclohexane

The slow secondary (beta) process of 1,1'-bis (4-methoxyphenyl) cyclohexane and phenolphthalein dimethylether has been investigated by dielectric spectroscopy. New experimental results about the pressure dependence of the two processes are reported, as well as new data about the dependence of the characteristic relaxation frequency on the cooling rate used to vitrify the system in isobaric conditions. Previous investigations on these systems suggested that the first one is not a true Johari-Goldstein relaxation and both processes should originate from the flip flop motion of the phenyl ring. The results herein reported evidence that the characteristic frequency of the beta process of phenolphthalein dimethylether is more sensitive to pressure variation and to the vitrification procedure than that of 1,1'-bis (4-methoxyphenyl) cyclohexane. Such results suggest an intermolecular origin for the secondary process in phenolphthalein dimethylether and an intramolecular origin for the other one, which do not completely agree with the previous interpretation. We evidence that the microscopic mechanism at the basis of these two processes is still an open question, which should be debated on the basis of new experimental investigations. Z9