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Large-Area Nanosquare Arrays from Shear-Aligned Block Copolymer Thin Films
Kim, So Youn,Nunns, Adam,Gwyther, Jessica,Davis, Raleigh L.,Manners, Ian,Chaikin, Paul M.,Register, Richard A. American Chemical Society 2014 NANO LETTERS Vol.14 No.10
<P>While block copolymer lithography has been broadly applied as a bottom-up patterning technique, only a few nanopattern symmetries, such as hexagonally packed dots or parallel stripes, can be produced by spontaneous self-assembly of simple diblock copolymers; even a simple square packing has heretofore required more intricate macromolecular architectures or nanoscale substrate prepatterning. In this study, we demonstrate that square, rectangular, and rhombic arrays can be created via shear-alignment of distinct layers of cylinder-forming block copolymers, coupled with cross-linking of the layers using ultraviolet light. Furthermore, these block copolymer arrays can in turn be used as templates to fabricate dense, substrate-supported arrays of nanostructures comprising a wide variety of elements: deep (>50 nm) nanowells, nanoposts, and thin metal nanodots (3 nm thick, 35 nm pitch) are all demonstrated.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-10/nl502416b/production/images/medium/nl-2014-02416b_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl502416b'>ACS Electronic Supporting Info</A></P>
Log-Rolling Block Copolymer Cylinders
Kim, Ye Chan,Kim, Dong Hyup,Joo, Se Hun,Kwon, Na Kyung,Shin, Tae Joo,Register, Richard A.,Kwak, Sang Kyu,Kim, So Youn American Chemical Society 2017 Macromolecules Vol.50 No.9
<P>Shear is an effective method to create long-range order in micro- or nanostructured soft materials. When simple shear flow is applied, particles or polymer microdomains tend to align in the shear direction to minimize viscous dissipation; thus, transverse alignment (so-called log-rolling) is not typically favored. This is the first study to report the transverse alignment of cylinder-forming coil coil block copolymers. Poly(styrene-b-methyl methacrylate), PS PMMA, where the PS blocks form the matrix, can adopt a metastable PMMA hemicylindrical structure when confined in a thin film, and this hemicylindrical structure can orient either along the shear direction or transverse to the shear direction depending on the shearing temperature. A monolayer of PS PMMA forming full cylinders exhibits log-rolling alignment. This unusual log-rolling behavior is explained by the low chain mobility of the cylinder-forming PMMA block at low temperatures, which is direction of shear alignment. the critical quantity determining the</P>