Skip navigation
  • Home
  • Browse
    • Communities
      & Collections
    • Browse Items by:
    • Publication Date
    • Author
    • Title
    • Subject
    • Department
  • Sign on to:
    • My MacSphere
    • Receive email
      updates
    • Edit Profile


McMaster University Home Page
  1. MacSphere
  2. Open Access Dissertations and Theses Community
  3. Open Access Dissertations and Theses
Please use this identifier to cite or link to this item: http://hdl.handle.net/11375/25228
Title: Unstable Systems of Viscous and Elastic Polymer Thin Films
Authors: Niven, John
Advisor: Dalnoki-Veress, Kari
Department: Physics and Astronomy
Keywords: Physics;Soft matter
Publication Date: 2020
Abstract: The work presented in this thesis focuses on the study of viscous and elastic polymer thin films in initially unstable configurations. The systems are driven to flow viscously or deform elastically to minimize their free energy. Since these experiments take place on length scales at which gravity does not play a role, the physics is governed purely by surface tension and viscosity in the case of fluid films, or elasticity in the case of rigid films. It is also possible to combine hydrodynamics and elasticity, for example, a viscous film that flows in response to the bending energy of an elastic perturbation, or an elastic film deformed by the capillarity or flow of a fluid. Viscous flow in thin polymer films is studied in a system which is free-standing in air, meaning it has two fluid-air interfaces. Cylindrical holes are formed part way through a nano-scale polymer film, creating an unstable geometry with dissimilar surface areas at the two interfaces. When heated above its glass transition temperature, surface tension drives the film to flow to minimize its total excess surface area. The evolution is first dominated by fast vertical flow, which equilibrates Laplace pressure through the film by forming symmetric holes at each interface. Slow horizontal flow then becomes dominant, which continually reduces excess surface area by filling in the holes. A novel atomic force microscopy method is developed to monitor the two interfaces of a film as they flow, allowing the total free energy evolution of the system to be measured. The results agree with a hydrodynamic model developed to describe both stages of flow. Elastic instabilities, where a rigid film deforms in response to geometrical confinement, are studied in a free-standing bilayer system consisting of a thin film on a pre-strained elastic substrate. These instabilities include sinusoidal wrinkling of the capping film, or, since the entire bilayer is free-standing, global buckling, where the entire system deforms out-of-plane. The transition between wrinkling and buckling is found to depend on the thickness and moduli ratios of the films, as well as the pre-strain in the substrate. A simple model shows good agreement with experiments. Finally, the interaction between elasticity and viscosity is studied by measuring the flow of a viscous fluid perturbation driven by the bending energy of a rigid capping film. The experimental scaling of the perturbation size is in agreement with the theoretical prediction in the large perturbation limit.
URI: http://hdl.handle.net/11375/25228
Appears in Collections:Open Access Dissertations and Theses

Files in This Item:
File Description SizeFormat 
niven_john_f_202001_PhD.pdf
Open Access
6.89 MBAdobe PDFView/Open
Show full item record Statistics


Items in MacSphere are protected by copyright, with all rights reserved, unless otherwise indicated.

Sherman Centre for Digital Scholarship     McMaster University Libraries
©2022 McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8 | 905-525-9140 | Contact Us | Terms of Use & Privacy Policy | Feedback

Report Accessibility Issue