Secondary dynamics in glass formers: Relation with the structural dynamics and the glass transition

Prevosto, D.; Capaccioli, S.; Sharifi, Soheil; Kessairi, Khadra; Lucchesi, M.; Rolla, Pierangelo

doi:10.1016/j.jnoncrysol.2007.03.045

Cited by 34 publications

(56 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reaction of sample polarization to a change in the electric field is delayed, which can be observed as a relaxation process with characteristic relaxation time. In polymers, two or three relaxation processes are most often observed, which are denoted with greek letters α, β, γ [24][25][26][27][28][29][30]. The (structural) α-process usually corresponds to the glass transition.…”

Section: Introductionmentioning

confidence: 99%

Liquid crystal epoxy resins based on biphenyl group cured with aromatic amines - studied by dielectric spectroscopy

et al. 2013

View full text Add to dashboard Cite

In this paper we investigate the dielectric response of cured epoxy resins based on biphenyl group. We chose two monomers, which were earlier synthesised, containing the same mesogen but with long and short symmetric tails. They were cured with standard amines (DDM, DMAP). Firstly we optimised conditions of the curing process by dielectric and optical observation in situ. Small differences in the dynamics of the curing process were observed in different mixtures. For the four selected products we made dielectric measurements in a wide range of frequency and temperature. Although, generally, dielectric response is similar in all the cured materials, differences can be seen in the details. At lower temperatures, quite strong relaxation process is seen in all products, its low activation energy points towards a β-process, which appears in many polymers. The Havriliak-Negami formula was fitted to the data and characteristic parameters of the observed relaxation processes were compared in detail. In some cases the α-process also appears. We conclude how the longer spacer and the type of curing process influence the electrical properties of the resin.

show abstract

Section: Introductionmentioning

confidence: 99%

Liquid crystal epoxy resins based on biphenyl group cured with aromatic amines - studied by dielectric spectroscopy

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Thus, the difference in t b (T) between the pressurized OG and OG at ambient pressure in the glass state should be larger than that between the SG and OG at ambient pressure. This can be verified by examining some experimental t b (T) data of OG at ambient and elevated pressure such as poly(phenylglycidylether) (PPGE), 51 diglycidyl ether of bisphenol-A with M w = 380 g mol…”

Section: Nanometer Thin Filmsmentioning

confidence: 84%

Why is surface diffusion the same in ultrastable, ordinary, aged, and ultrathin molecular glasses?

Ngai

Paluch

Rodríguez-Tinoco

2017

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

Recently Fakhraai and coworkers measured surface diffusion in ultrastable glass produced by vapor deposition, ordinary glass with and without physical aging, and ultrathin films of the same molecular glassformer, N,N 0 -bis(3-methylphenyl)-N,N 0 -diphenylbenzidine (TPD). Diffusion on the surfaces of all these glasses is greatly enhanced compared with the bulk diffusion similar to that previously found by others, but remarkably the surface diffusion coefficients D S measured are practically the same. The observed independence of D S from changes of structural a-relaxation due to densification or finite-size effect has an impact on the current understanding of the physical origin of enhanced surface diffusion. We have demonstrated before and also here that the primitive relaxation time t 0 of the coupling model, or its analogue t b , the Johari-Goldstein b-relaxation, can explain quantitatively the enhancement found in ordinary glasses. In this paper, we assemble together considerable experimental evidence to show that the changes in t b and t 0 of ultrastable glasses, aged ordinary glasses, and ultrathin-films are all insignificant when compared with ordinary glasses. Thus, in the context of the explanation of the enhanced surface diffusion given by the coupling model, these collective experimental facts on t b and t 0 further explain approximately the same D S in the different glasses of TPD as found by Fakhraai and coworkers.

show abstract

“…Representative spectra of the other systems can be found in Refs. [13,18,[20][21][22][23][24]. The secondary relaxation was analyzed in terms of the symmetric ColeCole function.…”

Section: Resultsmentioning

confidence: 99%

“…Glassy PDE presents three different relaxation processes: a so called excess wing, and two secondary relaxations [18,19], that are interpreted in term of local motions of parts of the molecule [13,18,19]. Glassy PPGE shows two secondary processes, the slower being of JG type [20,21], and the faster probably related to local motion of the epoxy subunits. BMPC show two secondary relaxations in the glassy state whose molecular origin is not clear at all [19,22].…”

Section: Introductionmentioning

confidence: 99%

Effect of thermodynamic history on secondary relaxation in the glassy state

Sharifi¹,

Prevosto

Capaccioli

et al. 2007

Journal of Non-Crystalline Solids

Self Cite

View full text Add to dashboard Cite

Secondary dynamics in glass formers: Relation with the structural dynamics and the glass transition

Cited by 34 publications

References 21 publications

Liquid crystal epoxy resins based on biphenyl group cured with aromatic amines - studied by dielectric spectroscopy

Liquid crystal epoxy resins based on biphenyl group cured with aromatic amines - studied by dielectric spectroscopy

Why is surface diffusion the same in ultrastable, ordinary, aged, and ultrathin molecular glasses?

Effect of thermodynamic history on secondary relaxation in the glassy state

Contact Info

Product

Resources

About