NANOSTRUCTURED POLYMERIC THIN FILM: HARNESS TRANSITION BETWEEN 2D TO 3D FOR DESIGNED FUNCTIONALITIES
Polymer brushes are polymer chains tethered to a surface at sufficient coverage so that the resulting steric repulsion forces them to stretch outward. This 2D stretching of the polymer brushes gives them unique physical properties different from traditional polymer melts. Tuning of the brush configuration, especially at the nanoscale could make polymer brushes a useful functional coating in the fields like anti-fouling and lubrication which counted on their behavior at highly confined regime. Upon removal of lateral confinement through patterning, they would have quite rich response in terms of mechanical, physical properties that are distinct to their non-patterned form for the reduction of the lateral pressure. In short, the foundation of this materials then depends on the ability to harness such transition between 2D to 3D stretching which is the key for the development of advanced materials and devices for biotechnology and electronic/optical applications. In this work, we look forward to increasing the understanding in patterned polymer brushes and it started from the neutral polymer brushes. Brush nanopatterning was conducted using orthogonal process following either top-down or bottom-up approaches with patterned lines as small as 200 nm. The pattern morphology depends not only on the wetting properties of the areas adjacent to the pattern, but also on process history to which the sample has been exposed, especially related to solvent quality. Furthermore, we demonstrated the method to control crosslinking on the edges of the pattern and this leads to the non-ordinary stimuli-responsive behavior. Subsequently, the stability of non-patterned and nanostructured strong polyelectrolyte brushes is studied as a function of both brush character and the properties of a contacting liquid. Nanopatterned polymer brushes proved its value in showing that the chain dynamic is also a dominant factor in brush degrafting and it should also be considered besides the reaction kinetics. The finding inspired us to design polymer brushes with more complex configuration. To characterize them, we fabricated optical grating which has polymer brushes anchoring only on the sidewall. Such platform when working with neutral scattering should allow the reconstitution of the 3D brush profile provide more insight to complicated behavior. The knowledge obtained was also expanded horizontally to the two different fields. For liquid crystal elastomer patterning, it managed to create micro-objects with controlled actuation motion by simply changing the direction of the patterns. On the other hand, polyelectrolyte brushes found its application in the field of biophysics where it could act as a cushion to facilitate the spontaneous formation of the supported lipid bilayer with high transmembrane protein mobility.
Chemical engineering; Materials Science; Degrafting; Orthogonal process; Patterning; Polyelectrolyte brushes; Polymer brushes
Ober, Christopher Kemper
Escobedo, Fernando; Archer, Lynden A.
Ph. D., Chemical Engineering
Doctor of Philosophy
Attribution 4.0 International
dissertation or thesis
Except where otherwise noted, this item's license is described as Attribution 4.0 International