X-ray Photon Correlation Spectroscopy to Study Dynamics of Thin Polymer Films
Abstract
Polymers are known to display inherent spatio-temporal heterogeneity over a large length and time scale. Polymer thin films have been widely studied with the intention of understanding how finite size effects impact their glass transition or chain relaxation behaviour in polymers. Although, several techniques, like inelastic and quasi-elastic neutron scattering and NMR have been successfully used, in the past, to study dynamics in bulk polymers, they are not very effective in studying thin films. The advent of 3rd generation synchrotrons and X-ray free electron lasers (XFEL), with extremely high brilliance and high coherent X-ray flux, has provided an opportunity to study structural dynamics in polymer thin films with unprecedented spatial and temporal resolution. In this regard, the technique of X-ray photon correlation spectroscopy (XPCS) — the X-ray equivalent of dynamic light scattering — has significantly enhanced our understanding of dynamics of polymers both due to chain entanglement effects as well as due to its glassy nature. In this chapter we will discuss the basic aspects of coherent X-ray scattering, especially, those relevant to understanding of the technique of XPCS as it is utilized in both transmission and reflection geometry, including technical details regarding effective utilization of this technique. Finally, we will discuss the various applications of XPCS in studying both polymer and nanoparticle dynamics in entangled, un-entangled and glassy polymer thin films, especially how finite size effects unfold in these ultrathin films. We will conclude with a perspective about possible future directions, including those using XPCS at XFELs.
- Publication:
-
Advanced Characterization of Nanostructured Materials. Probing the Structure and Dynamics with Synchrotron X-Rays and Neutrons. Edited by Sunil K. Sinha
- Pub Date:
- April 2021
- DOI:
- 10.1142/9789811231513_0007
- Bibcode:
- 2021acnm.book..307M