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Surface-directed dewetting of a block copolymer for fabricating highly uniform nanostructured microdroplets and concentric nanorings
Farrell, Richard A.; Kehagias, Nikolaos; Shaw, Matthew T.; Reboud, Vincent; Zelsmann, Marc; Holmes, Justin D.; Sotomayor Torres, Clivia M.; Morris, Michael A.
Through a combination of nanoimprint lithography and block copolymer self-assembly, a highly regular dewetting process of a symmetric diblock copolymer occurs whereby the hierarchal formation of microdroplets and concentric nanorings emerges. The process is driven by the unique chemical properties and geometrical layout of the underlying patterned silsesquioxane micrometer-sized templates. Given the presence of nonpreferential substrate−polymer interactions, directed dewetting was utilized to produce uniform arrays of microsized droplets of microphase separated polystyrene-block-poly(methyl methylacrylate) (PS-b-PMMA), following thermal annealing at 180 °C. Microdroplets with diameters greater than 400 nm exhibited a hexagonal close-packed arrangement of nanodots on the surface with polydomain ordering. At the droplet periphery, the polydomain ordering was severely disrupted because of a higher in-plane radius of curvature. By reducing the droplet size, the in-plane radius of curvature of the microdroplet becomes significant and the PMMA cylinders adopt parallel structures in this confined geometry. Continuous scaling of the droplet results in the generation of isolated, freestanding, self-aligned, and self-supported oblique nanorings (long axis ∼250−350 nm), which form as interstitial droplets between the larger microdroplets. Optical and magnetic-based nanostructures may benefit from such hierarchal organization and self-supporting/aligned nanoring templates by combining more than one lithography technique with different resolution capabilities.
Keyword(s): Block copolymers; Directed dewetting; Graphoepitaxy; Microdroplet; Nanoimprint; Lithography; Nanoring; Polystyrene-block-poly(methyl methylacrylate); Silsesquioxane
Publication Date:
Type: Journal article
Peer-Reviewed: Yes
Language(s): English
Institution: University College Cork
Funder(s): Science Foundation Ireland
Citation(s): Farrell, R. A., Kehagias, N., Shaw, M. T., Reboud, V., Zelsmann, M., Holmes, J. D., Sotomayor Torres, C. M. and Morris, M. A. (2011) 'Surface-Directed Dewetting of a Block Copolymer for Fabricating Highly Uniform Nanostructured Microdroplets and Concentric Nanorings', ACS Nano, 5(2), pp. 1073-1085. doi: 10.1021/nn102720m
Publisher(s): American Chemical Society (ACS)
File Format(s): application/pdf
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First Indexed: 2018-09-20 06:31:20 Last Updated: 2018-09-20 06:31:20