Cetindag Semih, Bellini Beatrice, Li Ruipeng, Tsai Esther H R, Nykypanchuk Dmytro, Doerk Gregory S
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Department of Chemical Engineering, Columbia University, New York, New York 10027, United States.
ACS Nano. 2025 Jan 28;19(3):3726-3739. doi: 10.1021/acsnano.4c14499. Epub 2025 Jan 10.
With their ability to self-assemble spontaneously into well-defined nanoscale morphologies, block copolymer (BCP) thin films are a versatile platform to fabricate functional nanomaterials. An important challenge to wider deployment of BCPs in nanofabrication is combining precise control over the nanoscale domain orientation in BCP assemblies with scalable deposition techniques that are applicable to large-area, curved, and flexible substrates. Here, we show that spray-deposited smooth films of a nominally disordered BCP exhibit latent orientations, which can be prescriptively selected by controlling solvent evaporation during spray casting. Subsequent solvent vapor annealing triggers assembly toward highly ordered cylindrical morphologies along the pathway determined by solvent evaporation in the prior spray deposition stage. Faster evaporation promotes assembly of vertically oriented cylinders spanning the entire film thickness (100-300 nm). In comparison, slow solvent evaporation permits intermicellar aggregation and incipient cylinder formation in solution, which induces horizontal cylinder assembly upon annealing. The evaporatively controlled latent orientation mechanism presented herein elucidates how nonequilibrium phenomena during casting govern successive self-assembly pathways and facilitates a versatile method to dictate the domain orientation of BCP thin films on demand on flexible and highly curved substrates or in distinct pattern areas on the same substrate.
嵌段共聚物（BCP）薄膜能够自发地自组装成明确的纳米级形态，是制造功能性纳米材料的通用平台。BCP在纳米制造中更广泛应用面临的一个重要挑战是，将对BCP组件中纳米级畴取向的精确控制与适用于大面积、弯曲和柔性基板的可扩展沉积技术相结合。在此，我们表明，名义上无序的BCP的喷雾沉积光滑薄膜呈现出潜在取向，通过控制喷雾铸造过程中的溶剂蒸发可以规定性地选择这些取向。随后的溶剂蒸汽退火会触发沿着先前喷雾沉积阶段中由溶剂蒸发确定的路径组装成高度有序的圆柱形形态。更快的蒸发促进了跨越整个薄膜厚度（100 - 300纳米）的垂直取向圆柱体的组装。相比之下，缓慢的溶剂蒸发允许胶束间聚集并在溶液中初步形成圆柱体，这会在退火时诱导水平圆柱体组装。本文提出的蒸发控制潜在取向机制阐明了铸造过程中的非平衡现象如何控制连续的自组装路径，并促进了一种通用方法，可根据需求在柔性和高度弯曲的基板上或同一基板上的不同图案区域中确定BCP薄膜的畴取向。
