Abstract:Combined X-ray photon correlation spectroscopy (XPCS) and diffracted X-ray tracking (DXT) measurements of carbon-black nanocrystals embedded in styrene-butadiene rubber were performed. From the intensity fluctuation of speckle patterns in a small-angle scattering region (XPCS), dynamical information relating to the translational motion can be obtained, and the rotational motion is observed through the changes in the positions of DXT diffraction spots. Graphitized carbon-black nanocrystals in unvulcanized styre… Show more
“…The value of A represents the contrast of the speckles, which is mainly determined by the coherent length of the X-ray and the pixel size of the detector. 28,29 FIG. 2.…”
The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.
“…The value of A represents the contrast of the speckles, which is mainly determined by the coherent length of the X-ray and the pixel size of the detector. 28,29 FIG. 2.…”
The dynamics of lower disorder-order temperature diblock copolymer leading to phase separation has been observed by X ray photon correlation spectroscopy. Two different modes have been characterized. A non-diffusive mode appears at temperatures below the disorder to order transition, which can be associated to compositional fluctuations, that becomes slower as the interaction parameter increases, in a similar way to the one observed for diblock copolymers exhibiting phase separation upon cooling. At temperatures above the disorder to order transition TODT, the dynamics becomes diffusive, indicating that after phase separation in Lower Disorder-Order Transition (LDOT) diblock copolymers, the diffusion of chain segments across the interface is the governing dynamics. As the segregation is stronger, the diffusive process becomes slower. Both observed modes have been predicted by the theory describing upper order-disorder transition systems, assuming incompressibility. However, the present results indicate that the existence of these two modes is more universal as they are present also in compressible diblock copolymers exhibiting a lower disorder-order transition. No such a theory describing the dynamics in LDOT block copolymers is available, and these experimental results may offer some hints to understanding the dynamics in these systems. The dynamics has also been studied in the ordered state, and for the present system, the non-diffusive mode disappears and only a diffusive mode is observed. This mode is related to the transport of segment in the interphase, due to the weak segregation on this system.
“…Hereafter, we pay attention to the combined measurements of diffracted X‐ray tracking (DXT) with XPCS using a high‐brilliance pink beam. This technique was applied to detect the dynamics of carbon black nanocrystals embedded in styrene–butadiene rubber . Figure shows the geometry of the experimental set‐up for this technique and a schematic of the geometry of the DXT measurements.…”
Section: New Types Of Simultaneous Measurementsmentioning
Synchrotron radiation facilities have been established and become very familiar in the polymer community not only from academic but also industrial viewpoints. It is not so unusual now to conduct simultaneous measurements of small-angle X-ray scattering (SAXS) with other techniques such as wide-angle X-ray scattering, stress-strain, light scattering, and so forth. New techniques have also been established and have become more familiar in recent years. In this review, recent developments in polymer applications of synchrotron SAXS are summarized. Instrumental developments and progress in data analyses are reviewed from the following aspects: ultra-small-angle X-ray scattering, anomalous SAXS, X-ray photon correlation spectroscopy, new types of simultaneous measurements, grazing-incidence SAXS, new trends in nanoparticle analyses and industrial applications.
“…In many examples, however, because the materials being studied are at limits of very small or very hindered motions, this requirement limits the applicability of these techniques. In fact, measurements of the angular fluctuations of the constituent particles, not possible by XPCS or SVS, are the only way to measure the local viscous forces in glassy materials but hitherto have not been possible or have only been demonstrated in extremely limited cases (Shinohara et al, 2013).To address these shortfalls, Liang and collaborators have developed the new technique of rotational X-ray tracking (RXT) and demonstrated its power by applying it to a study of small crystalline particles nominally immobilized by the fact that they form a colloidal gel under appropriate conditions (Liang et al, 2014). A gel is an extended disordered network with jelly like structural properties.…”
mentioning
confidence: 99%
“…In many examples, however, because the materials being studied are at limits of very small or very hindered motions, this requirement limits the applicability of these techniques. In fact, measurements of the angular fluctuations of the constituent particles, not possible by XPCS or SVS, are the only way to measure the local viscous forces in glassy materials but hitherto have not been possible or have only been demonstrated in extremely limited cases (Shinohara et al, 2013).…”
Over the past two decades or so, there has been increasing interest and development in measuring slow dynamics in disordered systems at the nanoscale. Technologically, this interest stems from a desire to understand the stability and rheological behavior of emulsions and colloidal suspensions -materials of particular relevance to the food and consumer products industries, for example (Dave et al., 2007). More fundamentally, however, stability and nanoscale motion in these types of materials touch upon larger problems in science such as the nature of dynamics in glassy materials and the physics of jamming (Liu & Nagel, 1998). Some of the techniques that have been developed over recent years to study the dynamic properties of these materials include X-ray photon correlation spectroscopy (XPCS) (Dierker et al., 1998) and speckle visibility spectroscopy (SVS) (Dixon & Durian, 2003). Both of these techniques, however, when performed with X-rays that are particularly sensitive to motion at the nanoscale require stable and very bright coherent X-ray beams that limit their implementation to only large specialized X-ray facilities at select locations in the world. Another important limitation, and this also applies to direct imaging microscopy techniques performed with visible light on analogous systems at larger length scales, is that these measurements are only sensitive to changes in the exact spatial arrangement of the constituent particles and, unless pathologically novel particles are incorporated into the material under investigation, are not sensitive to the orientation or rotation of the particles. In many examples, however, because the materials being studied are at limits of very small or very hindered motions, this requirement limits the applicability of these techniques. In fact, measurements of the angular fluctuations of the constituent particles, not possible by XPCS or SVS, are the only way to measure the local viscous forces in glassy materials but hitherto have not been possible or have only been demonstrated in extremely limited cases (Shinohara et al., 2013).To address these shortfalls, Liang and collaborators have developed the new technique of rotational X-ray tracking (RXT) and demonstrated its power by applying it to a study of small crystalline particles nominally immobilized by the fact that they form a colloidal gel under appropriate conditions (Liang et al., 2014). A gel is an extended disordered network with jelly like structural properties. As such, one might think of the gel in its unperturbed state as being immobile. As demonstrated, however, by RXT, the ostensibly static colloidal particles in the colloidal gel actually undergo angular motion and the precise nature of observed rotational motion is a sensitive and unique measure of the nanoscale elastic properties of the gel network.The RXT technique requires a relatively high flux X-ray beam, though not a coherent X-ray beam, and crystalline colloidal particles that exhibit Bragg diffraction. The size of the particles can vary depending ...
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