From Chains to Monolayers: Nanoparticle Assembly Driven by Smectic Topological Defects

Abstract

In this article, we show how advanced hierarchical structures of topological defects in the so-called smectic oily streaks can be used to sequentially transfer their geometrical features to gold nanospheres. We use two kinds of topological defects, 1D dislocations and 2D ribbon-like topological defects. The large trapping efficiency of the smectic dislocation cores not only surpasses that of the elastically distorted zones around the cores but also the one of the 2D ribbon-like topological defect. This enables the formation of a large number of aligned NP chains, within the dislocation cores that can be quasi-fully filled without any significant aggregation outside the cores. When the NP concentration is large enough to entirely fill the dislocation cores, the LC confinement varies from 1D to 2D. We demonstrate that the 2D topological defect cores induce a confinement that leads to planar hexagonal networks of NPs. We then draw the phase diagram driven by NP concentration, associated with the sequential confinements induced by these two kinds of topological defects. Owing to the excellent large-scale order of these defect cores, not only the NP chains but also the NP hexagonal networks can be oriented along the desired direction, suggesting a possible new route for the creation of either 1D or 2D highly anisotropic NP networks. In addition, these results open rich perspectives based on the possible creation of coexisting NP assemblies of different kinds, localized in different confining areas of a same smectic film that would thus interact thanks to their proximity but also would interact via the surrounding soft matter matrix.

Structural Landscapes in Geometrically Frustrated Smectics

“…Driven by advances in surface control, there has been considerable renewed interest in exploiting the ability of smectics to repeatably self-assemble over device length scales by using surface patterning [7,8], topographical features such as grooves [9][10][11][12] or posts [13,14], confinement in droplets [15][16][17], or curved surfaces more generally [18], to produce emergent patterns [19,20] that are optically active as lenses, gratings [21], photonic crystals [20], or lithographic templates [22]. Moreover, defect structures in the texture act to efficiently trap dispersed microparticles or nanoparticles, making smectics useful for hierarchical [23][24][25] or synergistic [26] assembly processes that could potentially be adopted for metamaterial, sensor, or solar cell production. Since many of the remarkable properties of smectics arise because of the geometric and topological consequences of layering, they form a paradigmatic model system to understand geometric frustration in other lamellar phases such as block copolymers [27,28], membranes, and vesicles [29,30].…”

Making Smectic Defect Patterns Electrically Reversible and Dynamically Tunable Using In Situ Polymer‐Templated Nematic Liquid Crystals

“…Overall, the new approach we report may provide a means to increment electric reversibility and dynamic adjustability to the latest features emerging from assemblies of SmA defect patterns. [ 3,6,7,9,16,18,19,21 ]…”

“…As recently reported in defect‐free SmA LCs, [ 35,36 ] our work also raises the question regarding the morphology of the polymer network as a function of the type of SmA defect pattern and polymerization conditions (UV dose, curing temperature, monomer and photoinitiator concentrations), and its influence on the performances of the resulting composites. We hence anticipate that our findings will pave the way to the design of new voltage responsive LC‐based composite and hybrid nanostructured materials, [ 3,6,7,9,18,21 ] with advanced properties that are of topical relevance in materials science.…”

“…Over the past decade, the structuration of different LC phases into organized defect patterns has emerged as a promising approach to create new polymer/LC composites and nanostructured hybrid materials with tunable optical properties. [ 3–9 ] From this perspective, smectic A (SmA) LCs, characterized by orientational and one‐directional translational orders of the constitutive rod‐like mesogens, packed into layers normal to n , [ 2 ] have been of particular interest. SmA LCs may self‐assemble into organized defect structures such as focal conic domains (FCDs) when frustrated in systems which do not permit a uniform alignment of the layers, for example, between two surfaces with different orientations (anchoring conditions) of the director n in their vicinity.…”

Liquid Crystal Films as Active Substrates for Nanoparticle Control

“…The inter-NP spacing in the hexagonal network has been measured on rubbed PVA surface (without a LC) by combined spectrophotometric measurements and synchrotron Grazing Incidence X-ray Scattering (GISAXS). It is equal to 1.9 nm 20,[30][31][32] . If we analyze the red-shift of the plasmonic absorption of Figure 4 using the dipolar approximation (see "Materials and methods"), we find that the inter-NP gap decreases from 1.9 nm without LC 20,30-32 to 1.1nm on top of PSNLC, leading to a shortening of 0.8 nm.…”