Condensed Exponential Correlation Functions in Multicomponent Polymer Blends Measured by X-ray Photon Correlation Spectroscopy

Ruegg, Megan L.; Patel, Amish J.; Narayanan, Suresh; Sandy, Alec; Mochrie, S. G. J.; Watanabe, Hiroshi; Balsara, Nitash P.

doi:10.1021/ma061183y

Cited by 18 publications

(27 citation statements)

References 78 publications

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“…X-ray photon correlation spectroscopy (XPCS) has emerged as a powerful tool for studying dynamic processes in colloidal [1][2][3][4][5] and polymeric [6][7][8][9][10] materials. XPCS exploits the partial coherence of x-ray beams produced at third generation synchrotron sources, resulting in speckle x-ray scattering patterns characteristic of the instantaneous distribution of electron density within the sample.…”

Section: Introductionmentioning

confidence: 99%

X-ray photon correlation spectroscopy during homogenous shear flow

et al. 2012

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We report x-ray photon correlation spectroscopy measurements of advective and diffusive dynamics in a dispersion of colloidal particles subjected to homogeneous shear flow in a rotating-disk shear cell. Intensity autocorrelation functions from scattering data collected using homodyne detection respond to the variation in velocity across the scattering volume when the scattering vector has a component parallel to the flow direction. Theoretical expressions for the impact of homogenous shear flow on the correlation function provide a quantitative prediction of the dependence of correlation functions on the scattering vector and shear rate. Under most circumstances, the applied shear deformation dominates the decay of the intensity correlation function. When scattering data are collected perpendicular to the flow direction, it is possible to measure the diffusive dynamics of the particles free from effects of the superimposed shear flow; however, this approach only works below some upper shear rate limit, beyond which data are affected either by shear effects (caused by the finite width of the detector) or by particle transit through the scattering volume.

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Section: Introductionmentioning

confidence: 99%

X-ray photon correlation spectroscopy during homogenous shear flow

et al. 2012

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“…However, for the SPS-8-57K molecules the values of α XPCS are much smaller, throughout the entire temperature range, suggesting a broader distribution of relaxation times. 27 With the use of molecular dynamics simulations, we recently showed that due to their architecture and associated monomer packing frustrations, the dynamics of star-shaped polymers would be characterized by broader distributions of relaxation times than their linear chain analogs: dynamics are slower at the vicinity of the branched point (higher monomer density) and become faster towards the arm end (lower monomer density). 15 The distribution becomes broader as functionality increases and/or when the arm is shorter.…”

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confidence: 99%

Free Surface Relaxations of Star-Shaped Polymer Films

et al. 2017

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The surface relaxation dynamics of supported star-shaped polymer thin films are shown to be slower than the bulk, persisting up to temperatures at least 50 degrees above the bulk glass transition temperature Tgbulk. This behavior, exhibited by star-shaped polystyrenes (SPSs) with functionality f = 8-arms and molecular weights per arm Marm < Me (Me is the entanglement molecular weight), is shown by molecular dynamics simulations to be associated with a preferential localization of these macromolecules at the free surface. This new phenomenon is in notable contrast to that of linear chain polymer thin film systems where the surface relaxations are enhanced in relation to the bulk; this enhancement persists only for a limited temperature range above the bulk Tgbulk. Evidence of the slow surface dynamics, compared to the bulk, for temperatures well above Tg and at length and time scales not associated with the glass transition has not previously been reported for polymers.

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“…105,106 Finally, we would refer to the present situation of synchrotron radiation beamlines for microbeam Xray scattering in Japan. There exist beamlines used for microbeam SAXS/WAXS experiments.…”

Section: Perspectivesmentioning

confidence: 99%

Application of Microbeam Small- and Wide-angle X-ray Scattering to Polymeric Material Characterization

Nozue

Shinohara

Amemiya

2007

Polym J

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ABSTRACT:With the recent development of an X-ray source, focusing optics, and X-ray detectors, microbeam Xray scattering techniques have been well established and widely applied to the characterization of polymeric materials. Microbeam X-ray scattering is a unique and powerful tool that provides abundant information on local structures, such as the spatial inhomogeneity of materials and the structural change at a local position. Furthermore, by combining microbeam small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS), the observable spatial scale range is from several to several hundred Å , which is the most important scale range in the hierarchical structure analyses of polymers. In this review, the representative applications of microbeam X-ray scattering to polymer crystallization, spatial inhomogeneity analyses, stress transfer under external field and the microphase separated structure analyses in block copolymer systems are introduced. [doi:10.1295/polymj.PJ2007077] KEY WORDS Microbeam Small-and Wide-angle X-ray Scattering / Polymer Characterization / X-Ray scattering techniques are widely applied to the observation of various polymer structures. X-Ray scattering is mainly classified into small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS), depending on the scattering angle. As is easily understood by using the Bragg formula ( ¼ 2d sin ), when the scattering angle 2 decreases, scattering reflects a large structure. SAXS, which is X-ray scattering at small angle (< 2, 3) region, provides information on nanostructures in a size range of several to several ten nanometers. In the field of polymeric materials, SAXS is typically applied to obtaining information on crystalline lamella stacking structures, 1,2 various microphase separated structures in block copolymer systems, 3,4 and organic-inorganic composite structures. 5,6 On the other hand, WAXS is typically applied to obtaining information on sub-nanometerscale structures, such as crystal packing and amorphous structures.To determine the structural characteristics of polymeric materials in detail, it is also very important to understand the formation and/or deformation mechanisms of such materials. Although X-ray scattering experiments were limited to the static measurements in laboratory X-ray sources until early 1980s, the advent of a synchrotron X-ray source and the development of X-ray detectors 7-13 have enabled us to observe a one-or two-dimensional scattering pattern within a second, making it possible to perform timeresolved X-ray scattering measurements for various structural changes, such as crystallization, 14-17 structural changes due to deformation [18][19][20][21][22][23] and phase transition due to temperature change. [24][25][26] While many polymeric materials exhibit spatial inhomogeneity on a micrometer scale, conventional X-ray scattering techniques provide the information that is spatially averaged over more than hundreds micrometer of the sample area irradiated by X-ray beam. Structural inmhom...

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Condensed Exponential Correlation Functions in Multicomponent Polymer Blends Measured by X-ray Photon Correlation Spectroscopy

Cited by 18 publications

References 78 publications

X-ray photon correlation spectroscopy during homogenous shear flow

X-ray photon correlation spectroscopy during homogenous shear flow

Free Surface Relaxations of Star-Shaped Polymer Films

Application of Microbeam Small- and Wide-angle X-ray Scattering to Polymeric Material Characterization

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