Tailoring adhesion and wettability of thin polymer films with surface-active bottlebrush polymer additives

We designed surface-active poly(tert-butyl acrylate-co-styrene) bottlebrush additives for polystyrene films. The additives preferentially enrich the surface and substrate interfaces of the solution-cast film. This behavior is attributed to a combination of effects: an entropic preference for the branched bottlebrush architecture at surfaces and interfaces; the inclusion of low energy tert-butyl acrylate moieties; and unfavorable enthalpic interactions between the bottlebrush additive and the polystyrene host. Subsequent thermal annealing activates a deprotection reaction that converts t-butyl acrylate to acrylic acid, increasing both surface wettability and adhesion to the underlying silicon substrate. This work demonstrates a method to tailor surface properties by using a combination of energetic and entropic effects to drive additives toward interfaces, followed by a simple post-deposition reaction to increase the additive’s polarity and tailor related functions.