Rheo-XPCS

Abstract

We review recent efforts and discuss future prospects in research employing x-ray photon correlation spectroscopy (XPCS) to interrogate the nanometer-scale structural dynamics of soft materials undergoing in situ mechanical deformation and flow. Examples of such rheo-XPCS experiments include those incorporating conventional homogeneous shear deformation, including notably large amplitude oscillatory shear (LAOS), as well as other modes of flow and deformation, such as tensile strain and flow within microfluidic environments. Particular attention is given to opportunities in such studies to reveal the structural dynamics associated with nonlinear rheological behavior such as yielding. We also review recent related work employing XPCS as a microrheological tool by tracking nanoparticle mobility within complex fluids.

Synchrotron Scattering Methods for Nanomaterials and Soft Matter Research

“…However, there are limitations in terms of q range and concentrations which can be studied, especially when the sample becomes turbid. With the advent of third generation synchrotron sources, XPCS has emerged as an alternative method for probing the equilibrium dynamics in such systems [9,[103][104][105]. The XPCS technique exploits the coherence properties of the X-ray beam and the measured scattering patterns display speckles as shown in Figure 12.…”

“…The multispeckle XPCS is also a valuable tool for analysing the direction dependent dynamics, as illustrated in the case of shear flow [103] and sedimentation [110], where g 2 (q, t) involves both diffusive and advective contributions. Disentangling the information requires simultaneous measurements at many q values both along the vertical and horizontal directions.…”

“…For example, elucidating the order-disorder transition underlying shear thickening in dense suspensions of colloidal particles subjected to different oscillatory shear stresses [119]. When combined with large amplitude oscillatory shear, XPCS can detect nonlinear rheological behavior such as yielding and plastic flow during an oscillation [103]. For example, the local signature of yielding during large amplitude oscillatory shear has been detected in concentrated oil-in-water nanoemulsions [120].…”

Coupling Space-Resolved Dynamic Light Scattering and Rheometry to Investigate Heterogeneous Flow and Nonaffine Dynamics in Glassy and Jammed Soft Matter

“…In XPCS, it has been used to measure the Brownian dynamics of colloids pumped in a capillary [72], a scheme aiming at minimizing the sample exposure to the intense X-ray radiation, which often causes radiation damage. XPCS has also been used to investigate the yielding transition of colloidal gels submitted to an oscillatory shear deformation [73,74], where the single scattering geometry allowed the authors to study the dynamics in the directions parallel and perpendicular to the flow direction and within each cycle, not just stroboscopically. The ability of resolving non-affine microscopic dynamics thanks to single scattering is also at the core of the small-angle DLS setup described in Refs.…”

Scaling Behavior of Anisotropy Relaxation in Deformed Polymers

“…Historically, the development of quasi-elastic neutron scattering techniques has provided a powerful tool for understanding the microscopic details of polymer motions in the quiescent state, where the spatial and temporal dependence of dynamics is encapsulated in the measured coherent and incoherent dynamic structure factors or corresponding intermediate scattering functions in Fourier space [1][2][3]. The application of quasi-elastic scattering to polymers undergoing mechanical deformation and flow, however, has so far been limited by serious theoretical and practical difficulties, despite some technical progress [4][5][6][7]. In this context, time-resolved small-angle scattering, based on either ex-situ or in-situ methods, presents an alternative approach to elucidating the microstructure of polymers in the deformed state.For quasi-elastic scattering, dynamic structure factors and intermediate scattering functions [F (Q, t)] provide a convenient mathematical language for describing the spatiotemporal dependence of molecular dynamics [3].…”