Block Copolymer (BCP) Self-Brushing The value of 𝜙 was chosen to be 0.365, which is the equal surface energy condition that was determined via island-hole tests. The pitch of the BCP, 𝐿 " , was determined via bulk small angle X-ray scattering experiments and was found to be 𝐿 " = 19.9 nm (see Supporting Information). Figure shows the evolution of structure of BCP films that are self-brushed on top of pristine native oxide Si substrates. Figure shows AFM images of a BCP film with 𝑡 = 1.87𝐿 " = 36 nm, F1, where we observe a parallel lamellar structure indicating that Si is a preferential substrate for one block of the BCP. The AFM image also shows the characteristic island formation of parallel oriented films of incommensurate thickness. In this case, the islands have step-heights of 1𝐿 " and 0.5𝐿 " indicative of a non-preferential wetting at the top, free interface. Upon rinsing, a non-structured polymer monolayer, M1, is observed. After application of a second polymer film, F2, the same island structure indicative of a preferential substrate for one block of the BCP is observed and a second non-structured monolayer, M2, is observed following subsequent film rinsing (Figure ). Figure shows tracking of the film thickness (blue, left yaxis) and water contact angle (WCA, red, right y-axis) through the 2 rounds of film application.