Surface instabilities in polymer thin films have received increasing attention due to the ability to generate well-defined and complex topological features. The formation of highly ordered surface wrinkles represents one class of instability-drive phenomena, and examples are readily available in nature, such as wrinkling in skin or dried fruit. Following nature’s lead, strain-induced wrinkling of polymer films has emerged as a powerful technique to design materials for various applications in advanced adhesion, antifouling, and flexible electronics. Herein, we demonstrate a simple route to design ultrathin polymer brush surfaces with tunable wrinkled morphologies using post-polymerization modification (PPM) techniques, where the length scale of the buckling features can be tuned using PPM time. The PPM reaction occurs under poor solvent conditions, which collapses the brush and partially crosslinks the brush at the near-surface region. This PPM reaction occurs in a front-like process, forming a diamine-modified “skin” thickness (h1) and an unmodified “substrate thickness” (h2). The swelling behavior of the polymer brushes and PPM kinetics can be investigated using in-situ ellipsometry, and the through-thickness brush composition is determined by time-of-flight secondary ion mass spectroscopy (ToF-SIMS). These techniques allow us to determine the parameters that influence the buckling behavior. Additionally, the wrinkle orientation can be controlled by AFM lithography techniques.

Tailoring buckling instabilities in ultrathin polymer brush surfaces

2019 Spring National Meeting

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