Kinetic viscoelasticity during early polymer-polymer spinodal dewetting

• Published in: Physical review research 2021-12, Vol.3 (4), p.043162, Article 043162
• Main Authors: Lal, J., Lurio, L. B., Liang, D., Narayanan, S., Darling, S. B., Sutton, M.
• Format: Article
• Language: English
• ISSN: 2643-1564; 2643-1564
• DOI: 10.1103/PhysRevResearch.3.043162

The dewetting kinetics of a supported polymer bilayer were measured in situ using coherent grazing-incidence x-ray scattering. X-ray photon correlation spectroscopy provides both the two-time correlation functions and the cross-correlation function which measures the average spatial shift of the speckles produced by the coherent x rays. The stress in the ultrathin top dewetting film can be directly observed due to the exquisite sensitivity to sample curvature changes provided by the x-ray speckle correlation functions. The hole-opening events in the film are found to be associated with significant changes to the stress. These results are interpreted through an analogy between viscoelastic spinodal dewetting and early-stage bulk viscoelastic phase separation. The frequency of hole-initiation events during dewetting decreases with time as a power law, and the power-law exponent can be linked to nonlinear viscoelastic effects, showing similarity in their stress relief dynamics to aftershock decays.