Glassy system dynamics properties

The concept of fragility is a qualitative one and is related to deviations of the relaxation time of a liquid from Arrhenius-like behavior and to the topology of the potential energy landscape of the system. The classification of liquids into strong and fragile thus provides a fundamental framework for quantitatively describing equilibrium and dynamical properties of supercooled liquids and glassy states of matter [1-6,8,9,22,37,38,52,54—56,88-91,103]. 

Del Popolo and Voth computed dynamical properties at 400 K and observed very long overall rotational relaxation times, consistent with the slow dynamics observed by Margulis, Stern, and Berne as well as by Morrow and Maginn. They showed the clearest evidence up to that point that the dynamic motion of ionic liquids bears a resemblance to that of supercooled or glassy systems, an issue that will be described more fully later in this chapter. 

Experiments in confined geometries, particularly in the case of polymers, require several considerations. Besides the existence or absence of interfaces, the geometry itself plays an important role. ID confinement geometiy (thin films) and 2D confinement (nanotubes and nanorods) implies that the polymer chain has to accommodate in an anisotropic fashion, whereas in 3D (nanospheres) the confinement is isotropic. In each of the above mentioned experiments, interfaces play a fundamental role. In the particular case of ID confinement, as for supported thin films, it has been demonstrated that there is a strong impact of interfaces on the static and dynamical properties of the polymer [38]. These interfaces also appear in the case of polymers confined in cylindrical pores. Tanaka and coworkers demonstrated that the slower dynamics near a substrate is related to a wall-induced enhancement of glassy structural order , which is a manifestation of strong interparticle correlations [39]. The presence of the solid interface favours the presence of clusters with a preferential bond orientational order. When the polymer system under these circumstances is semicrystaUine, the crystallization process is modified in two different ways. On one hand, the slower dynamics due to the polymer-chain interactions delays the crystallization process [12, 20]. On the other... 

In addition, many of the ferroelectric solids are mixed ions systems, or alloys, for which local disorder influences the properties. The effect of disorder is most pronounced in the relaxor ferroelectrics, which show glassy ferroelectric behavior with diffuse phase transition [1]. In this chapter we focus on the effect of local disorder on the ferroelectric solids including the relaxor ferroelectrics. As the means of studying the local structure and dynamics we rely mainly on neutron scattering methods coupled with the real-space pair-density function (PDF) analysis. 

In the present study, the effects of composition, molecular weight, and heat treatment on the relaxation behavior of styrene—butadiene-styrene (SBS) block polymers are investigated. There is evidence (e.g., 6,7,8) that these types of multicomponent multiphase systems exhibit unusual phenomena in their dynamic mechanical behavior and in other physical properties. These are apparently related to the presence of the so-called interphase mixing region between the elastomeric and glassy domains. Similar evidence has been obtained by gas diffusion and sorption studies on the copolymer samples used in this investigation (9). 

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