Arrested coalescence drives helical coiling and networking of filamentous smectic condensates

TL;DR

This study uncovers how filamentous smectic liquid crystal condensates form complex networks through arrested coalescence, driven by interfacial energy minimization and smectic constraints, resulting in spontaneous helical coiling.

Contribution

It reveals a novel mechanism of network formation in smectic liquid crystals involving filament linking and helical coiling driven by arrested coalescence, supported by experiments and modeling.

Findings

Filaments snap into contact and wind into helices without molecular chirality.

Arrested coalescence depends on interfacial energy and smectic order.

Networks form through spontaneous filament coiling driven by energy minimization.

Abstract

Liquid-liquid crystal phase separation (LLCPS) occurs in many industrial and biological settings. To date the states of the separated condensed liquid crystals have been found to be nematic, columnar, or smectic phases. Interestingly, when smectic phases condense out of the liquid, they can form filamentous condensates that spontaneously assemble into sparse networks with rich life-like dynamics. Here, we study the underlying process of filament linking and conformational changes that mediates formation of these unique networks. Microscopy reveals that new linkages between filaments are initiated by an adhesive interaction between straight filaments; the filaments snap into contact and then rapidly wind into helical coils, despite the absence of molecular chirality or transitions between mesophases. Using polarized optical microscopy, theoretical modeling, and simulation, we show that filament linking into ribbon structures is driven by arrested coalescence that depends on both interfacial energy minimization and the constraints of smectic order. The linked filaments spontaneously coil into double helices to reduce interfacial area and smectic distortion, thus driving compaction into networks. We propose a microstructure consistent with this interpretation, which quantitatively predicts the extent of arrested coalescence. In total, these findings suggest a generic pathway for network formation in liquid crystals that provides insight about the formation of condensate networks in other engineered or biological materials.