Secondary molecular mobility in amorphous ethyl cellulose: Aging effects and degree of co‐operativity

Abstract

The secondary relaxations in amorphous ethyl cellulose are studied using thermally stimulated depolarization currents (TSDCs) in the temperature region from 165 °C (108 K) up to 145 °C (418 K). The influence of aging on the current peaks of the secondary relaxation is discussed, and it is concluded that some modes of motion of this mobility are aging independent, while others are affected by aging. A particular attention is focused on the discussion of the degree of co‐operativity of the motional modes of the secondary relaxation. The conclusion to be driven from the obtained TSDC results is that the aging‐independent motional modes, as well as those that are aging dependent, do not show any appreciable co‐operative character. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 820–829, 2009

The ionic liquid BmimBr: a dielectric and thermal characterization

“…Let us finally note that while the DRS technique provides no more than an average activation energy, TSDC gives information regarding the distribution of relaxation times in this secondary process, showing that it is distributed in energy, and not in entropy (which means that the pre-exponential factors have values near the Debye time). 55 Additionally, the present work represents a further example where it is shown that a genuine b JG process is non-cooperative in nature in agreement with the result claimed by some of us 55,56 for other kind of materials.…”

Contribution of the technique of thermostimulated currents for the elucidation of the nature of the Johari-Goldstein and other secondary relaxations in the vitreous state

“…In this context it seems reasonable to consider that those motional modes have an intermolecular origin, and correspond to the Johari-Goldstein relaxation. The results by TSDC presented before (and those obtained on other glass-forming systems [29,34,35]) are in full agreement with those of Johari [36] obtained by DRS: the effect of annealing near but below T g on the secondary relaxation is predominantly a decrease of the loss, without any significant shift of its spectrum. In fact, in contrast with the aging behavior of the glass transition relaxation, the TSDC results indicate that the relaxation times of all the secondary relaxations ( JG ,   , …) appear as nearly independent of aging, in agreement with other reports [37] and in contradiction with the interpretation of some results obtained by dielectric relaxation spectroscopy reporting that  JG of the Johari-Goldstein relaxation mimics the increase of  GT with aging [38].…”

Influence of hydrogen bonds on glass transition and dielectric relaxations of cellulose

“…Its kinetics must be fast since it is independent from annealing time contrarily with usual physical ageing. It is interesting to report here that physical ageing has been observed by thermo stimulated currents in amorphous ethyl cellulose [47]. At this stage, the phenomenon observed in cellulose may be attributed to the disruption of hydrogen bonds in the amorphous phase.…”