Self-assembling materials are the building blocks of bottom-up nanofabrication processes, but they need to be templated to impose long-range order and eliminate defects. In this work, the self-assembly of a thin film of a spherical-morphology block copolymer is templated using an array of nanoscale topographical elements that act as surrogates for the minority domains of the block copolymer. The orientation and periodicity of the resulting array of spherical microdomains are governed by the commensurability between the block copolymer period and the template period and is accurately described by a free-energy model. This method, which forms high-spatial-frequency arrays using a lower-spatial-frequency template, will be useful in nanolithography applications such as the formation of high-density microelectronic structures.

We take advantage of self‐assembly in a hierarchically structured, hybrid material to develop photonic bandgaps in the visible which may be systematically tuned by application of thermal or electric fields. Hydrogen bonding between a host polymer and a guest small molecule is used to augment the molecular weight of an appropriately selected coil–coil diblock copolymer to bring the microdomain structure onto the length scale needed for significant interaction with visible light. Further, the use of liquid‐crystal‐mesophase‐forming moieties as the guest hydrogen‐bonding units adds functionality to the system as the optical properties of the liquid‐crystalline domains can be modulated by external stimuli. We use hydrogen bonding to sequester varying amounts of imidazole terminated mesogens within the acid domains of a poly[styrene‐block‐poly‐(methacrylic acid)] (PS‐b‐MAA) diblock copolymer. The resulting PS‐b‐MAA/LC side‐group liquid‐crystalline diblock copolymer possesses a photonic bandgap in the green with the exact location and structure of the gap dependent on the composition of the system. Here, we discuss the structure and optical properties of these materials as a function of their composition and the response of the optical properties to temperature. Varying the order parameter of the LC domains by heating into the isotropic state changes the peak reflectivity by 40 nm, resulting in a color change from green to orange.

Articles you may be interested inBlock copolymer self assembly for design and vapor-phase synthesis of nanostructured antireflective surfaces J. Vac. Sci. Technol. B 32, 06FE02 (2014); 10.1116/1.4896335Directed self-assembly of ternary blends of block copolymer and homopolymers on chemical patterns J. Vac. Sci. Technol. B 31, 06F301 (2013); 10.1116/1.4818882 Curing process of silsesquioxane in self-organized diblock copolymer template Block copolymers can self-assemble to generate patterns with nanoscale periodicity, which may be useful in lithographic applications. Block copolymers in which one block is organic and the other contains Si are appealing for self-assembled lithography because of the high etch contrast between the blocks, the high etch resistance of the Si-containing block, and the high Flory-Huggins interaction parameter, which is expected to minimize line edge roughness. The locations and long range order of the microdomains can be controlled using shallow topographical features. Pattern generation from poly͑styrene͒-poly͑ferrocenyldimethylsilane͒ and poly͑styrene͒-poly͑dimethyl-siloxane͒ block copolymers, and the subsequent pattern transfer into metal, oxide, and polymer films, is described.

3D nanostructured quasicrystalline materials significantly larger than feasible with previously reported techniques are produced. 2D quasiperiodic surface relief templates with 8mm point group symmetry are made by multiple‐exposure interference lithography. Phase‐mask lithography with corresponding PDMS masks produce bicontinuous 3D axial quasicrystal SU‐8 structures (see figure).

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