Alladi Ramakrishnan Hall

Programming Colloidal Self-Assembly for Open Crystals and Empty Liquids

Dwaipayan Chakrabarti

University of Birmingham

Colloidal open crystals — sparsely populated periodic structures, comprising low-coordinated colloidal particles — are attractive targets for self-assembly because of their variety of applications, for example, as photonic materials, phononic and mechanical metamaterials, as well as porous media [1-4]. Colloidal particles in their primitive form offer short-range isotropic interactions, and thus tend to form close-packed crystals. Despite the advances over the last two decades in the synthesis of colloidal particles, endowed with anisotropic and/or specific interactions [5-7], programming self-assembly of colloidal particles into open crystals has proved elusive. In this presentation, I will first talk about a series of computational studies that establish facile bottom-up routes for rationally designed patchy particles to self-assemble into a variety of colloidal open crystals, especially those much sought-after as photonic crystals [8-12]. The strategies include encoding hierarchical self-assembly pathways and ring size selection, in close connection with advances in colloid synthesis. I will also talk about how hierarchical self-assembly of designer patchy particles can instead be exploited to develop a colloidal model of water – a classic example of empty liquids [13]. I will demonstrate how this colloidal model unravels a novel topological distinction in terms of entanglement between the two liquids of different densities involved in the liquid-liquid phase transition (LLPT) [13] – originally hypothesised in connection with the host of anomalous thermodynamic properties in water [14]. Finally, I will illustrate how entanglement can emerge as a general mechanism for densification with a hierarchy of topological transitions in a network liquid, which is known to densify via two successive LLPTs [15].
References
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[15] A. Neophytou, F. W. Starr, D Chakrabarti and F. Sciortino, Proc. Natl. Acad. Sci. USA, 2024, 121, e2406890121.