Michman, E. ; Oded, M. ; Shenhar, R. Dual Block Copolymer Morphologies in Ultrathin Films on Topographic Substrates: The Effect of Film Curvature.
Polymers 2022,
14, 2377.
DOIAbstractThe ability to create mixed morphologies using easily controlled parameters is crucial for the integration of block copolymers in advanced technologies. We have previously shown that casting an ultrathin block copolymer film on a topographically patterned substrate results in different deposited thicknesses on the plateaus and in the trenches, which leads to the co-existence of two patterns. In this work, we highlight the dependence of the dual patterns on the film profile. We suggest that the steepness of the film profile formed across the plateau edge affects the nucleation of microphase-separated domains near the plateau edges, which influences the morphology that develops on the plateau regions. An analysis of the local film thicknesses in multiple samples exhibiting various combinations of plateau and trench widths for different trench depths enabled the construction of phase diagrams, which unraveled the intricate dependence of the formed patterns not only on the curvature of the film profile but also on the fraction of the film that resides in the trenches. Our analysis facilitates the prediction of the patterns that would develop in the trenches and on the plateaus for a given block copolymer film of known thickness from the dimensions of the topographic features.
![64. Elisheva curvature effect 64. Elisheva curvature effect](https://scholars.huji.ac.il/sites/default/files/styles/os_files_xxlarge/public/royshenhar/files/64._elisheva_curvature_effect.jpg?m=1655106581&itok=yinkIBYx)
Muzaffar-Kawasma, R. ; Oded, M. ; Shenhar, R. Assembly of Semiconductor Nanorods into Circular Arrangements Mediated by Block Copolymer Micelles.
Materials 2022,
15, 2949.
DOIAbstractThe collective properties of ordered ensembles of anisotropically shaped nanoparticles depend on the morphology of organization. Here, we describe the utilization of block copolymer micelles to bias the natural packing tendency of semiconductor nanorods and organize them into circularly arranged superstructures. These structures are formed as a result of competition between the segregation tendency of the nanorods in solution and in the polymer melt; when the nanorods are highly compatible with the solvent but prefer to segregate in the melt to the core-forming block, they migrate during annealing toward the core–corona interface, and their superstructure is, thus, templated by the shape of the micelle. The nanorods, in turn, exhibit surfactant-like behavior and protect the micelles from coalescence during annealing. Lastly, the influence of the attributes of the micelles on nanorod organization is also studied. The circular nanorod arrangements and the insights gained in this study add to a growing list of possibilities for organizing metal and semiconductor nanorods that can be achieved using rational design.
Eren, N. ; Burg, O. ; Michman, E. ; Popov, I. ; Shenhar, R. Gold Nanoparticle Arrays Organized in Mixed Patterns Through Directed Self-assembly of Ultrathin Block Copolymer Films on Topographic Substrates.
Polymer 2022,
245, 124727.
DOIAbstractControlling complexity in assemblies of metal and semiconductor nanoparticles has the potential to expand the utilization of photonic devices into wavelength regimes that are currently inaccessible. Here we show that casting ultrathin films of asymmetric block copolymers on topographically defined substrates affords four types of mixed patterns through fine control of film thickness. Analysis of top-view and cross-sectional images revealed different morphological behavior of the film in the trench and on the plateau, which was explained by the difference in the type of boundary imposed by each topographic feature. Exposed domains were chemically modified and selectively decorated with gold nanoparticles, giving rise to nanoparticle superstructures with mixed patterns in a controlled fashion. We envisage utilization of such hierarchical superstructures as plasmon waveguides and metasurfaces.