Tailoring Surface Properties of Polymer Films with Bottlebrush Copolymers

Bottlebrush polymers are a class of branched polymers with polymeric side chains densely grafted to a linear backbone. Due to their tunable chemistry and architecture, bottlebrush polymers can be used as surface-active additives that tailor surface properties, or as thin film coatings that mimic the functions of surface-attached polymer brushes. My research has encompassed the design, synthesis, and characterization of bottlebrush copolymers having a mixture of polystyrene (PS) and poly(2- vinylpyridine) (P2VP) side chains. PS is hydrophobic with a low surface energy, while P2VP is hydrophilic with a high surface energy. This dissertation consists of two original research thrusts. The first thrust focuses on designing wetting reversal processes, wherein bottlebrush PS-co-P2VP accumulates at the surface of PS films despite an approximately 15% gain in surface energy. The wetting reversal is mediated by a strong entropic attraction of the bottlebrush copolymer towards surfaces. These studies establish the conditions where wetting reversals are thermodynamically stable, and it is anticipated that this knowledge could be extended to chemistries beyond PS and P2VP. The second research thrust focuses on the structure and surface properties of bottlebrush PS-co-P2VP, where the fraction of P2VP side chains and the molar composition of 2-vinylpyridine are independently varied. These materials have a mixture of PS and P2VP side chains at the surface when bottlebrush PS-co-P2VP is weakly segregated, while a PS wetting layer forms at the surface when bottlebrush PS-co-P2VP is more strongly segregated and able to self assemble into nanoscale domains. In the limit of weak segregation, wettability and surface energy scale with the fraction of P2VP side chains.