Abstract
Chiral liquid crystals, or cholesteric phases, have been widely studied in the last decades, leading to fundamental advances and a multitude of applications and technologies. In general, the rich phenomenology of these systems depends directly on the molecular traits and conditions of the system, imposing precise symmetry to the resulting nematic field. By selecting amyloid fibrils as model filamentous chiral colloids, we report an unprecedented breadth of liquid crystalline morphologies, where up to six distinct configurations of the nematic field are observed under identical conditions. Amyloid-rich droplets show homogeneous, bipolar, radial, uniaxial chiral and radial chiral nematic fields, with additional parabolic focal conics in bulk. Variational and scaling theories allow rationalizing the experimental evidence as a subtle interplay between surface and bulk energies. Our experimental and theoretical findings deepen the understanding of chiral liquid crystals under confinement, opening to a more comprehensive exploitation of these systems in related functional materials.
Highlights
Liquid crystals are a class of materials that combine the long-range order typical of solids with the fluidity of liquids
Apart from the three cases reported by Nystrom et al.[6], the aggregates show droplets with: (i) radial nematic symmetry; (ii) radial cholesteric and (iii) macroscopic bulk phases characterized by parabolic focal conics with discrete orientation of the nematic field
Beside the two order-order transitions already known, i.e. the homogeneous-bipolar and bipolar-uniaxial cholesteric transitions[6], we report and characterize a third and additional transition that amyloid tactoids spontaneously undergo in order to minimize the free energy, from uniaxial cholesteric to radial cholesteric
Summary
Liquid crystals are a class of materials that combine the long-range order typical of solids with the fluidity of liquids. It was found that destabilized dispersions of beta-lactoglobulin amyloid fibrils positioned within the Isotropic-Nematic biphasic region nucleate from an unstable isotropic phase into droplets displaying three different morphologies (homogeneous, bipolar, uniaxial cholesteric), depending on the volume of the tactoid.
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