Hexadecapolar colloids

TL;DR

This paper reports the creation of elastic hexadecapolar distortions in liquid crystal colloids, revealing complex anisotropic interactions driven by boundary conditions, expanding understanding of colloidal behavior beyond known multipolar distortions.

Contribution

It introduces the first observation of elastic hexadecapoles in colloids, demonstrating their unique bonding properties and physical formation mechanisms in nematic liquid crystals.

Findings

Hexadecapolar distortions induce anisotropic colloidal interactions.

Formation of hexadecapoles is driven by conically degenerate boundary conditions.

New bonding behaviors are observed that are inaccessible to lower-order multipoles.

Abstract

Outermost occupied electron shells of chemical elements can have symmetries resembling that of monopoles, dipoles, quadrupoles and octupoles corresponding to filled s-, p-, d- and forbitals. Theoretically, elements with hexadecapolar outer shells could also exist, but none of the known elements have filled g-orbitals. On the other hand, the research paradigm of "colloidal atoms" displays complexity of particle behaviour exceeding that of atomic counterparts, which is driven by DNA functionalization, geometric shape and topology and weak external stimuli. Here we describe elastic hexadecapoles formed by polymer microspheres dispersed in a liquid crystal, a nematic fluid of orientationally ordered molecular rods. Because of conically degenerate boundary conditions, the solid microspheres locally perturb the alignment of the nematic host, inducing hexadecapolar distortions that drive anisotropic colloidal interactions. We uncover physical underpinnings of formation of colloidal elastic hexadecapoles and describe the ensuing bonding inaccessible to elastic dipoles, quadrupoles and other nematic colloids studied previously.