Journal: Journal of Materials Chemistry. C

Article Title: Heads or tails: investigating the effects of amphiphile features on the distortion of chiral nematic liquid crystal droplets †

doi: 10.1039/d2tc05390j

Figure Lengend Snippet: The amount of chiral dopant added to an LC sample affects the pitch of the material and thus the outcome of switching. Droplets of liquid crystals prepared from (a) pure 5CB (4-cyano-4′-pentylbiphenyl), a nematic phase; (b) 3% w/w chiral dopant CB15 (( S )-4-cyano-4′-(2-methylbutyl)biphenyl) mixed into 5CB; and (c) 35% w/w CB15 in E7. In all cases, droplets are stabilized by 0.2% w/w PVA (unswitched) and exposed to 1.0 mM sodium dodecyl sulfate (SDS) solution (switched). The textures in (a) are the characteristic polar planar (unswitched) and “Maltese Cross” homeotropic (switched) that we expect for a nematic liquid crystal. In (b), the characteristic Frank–Pryce texture consisting of rings with helical axis orthogonal to the surface of the droplet changes to a “fingerprint” in presence of surfactants, where the helical axis of the LC lies along the surface of the droplet instead with interference patterns from both hemispheres. In (c), the effects of the unswitched Frank–Pryce texture manifest in the form of central droplet reflections with blue-shifted inter-droplet reflections (red to green), while the switched textures provide a complex, scattering pattern with complex color signatures. The alignment induced by the homeotropic nematic and the Frank–Pryce texture in the chiral nematic have been shown to penetrate through the droplet. However, the degenerate anchoring associated with the planar nematic and fingerprint chiral nematic are not assumed to impart as strong ordering within the droplet bulk. Scale bar 25 μm.

Article Snippet: We additionally used the nematic liquid crystal 5CB (4-cyano-4′-pentylbiphenyl, 95%+, Tokyo Chemical Industry) and the eutectic nematic liquid crystal blend E7 (51% 5CB, 25% 4-cyano-4′-heptylbiphenyl, 16% 4-cyano-4′-octyloxybiphenyl, and 8% 4-cyano-4′-pentyl- p -terphenyl ; Synthon GmbH) to create different CLC mixtures with variable pitch.

Techniques:

Journal: Journal of Materials Chemistry. C

Article Title: Heads or tails: investigating the effects of amphiphile features on the distortion of chiral nematic liquid crystal droplets †

doi: 10.1039/d2tc05390j

Figure Lengend Snippet: Using long pitch CLC materials can help us directly visualize how the pitch changes upon addition of amphiphiles. Droplets of a mixture of 3% w/w CB15 in 5CB were prepared in buffers containing (a) 0.02% w/w PVA, resulting in the characteristic Frank–Pryce texture associated with tangential LC/normal helical alignment visible at the droplet equator; and 1.0 mM each (b) lauric acid, (c) SDS, and (d) the phospholipid DOPC, where the LC is normally aligned and thus the helical modulation occurs tangentially along the LC surface, resulting in a characteristic “fingerprint” texture. Insets and white lines indicate a sample of how the pitch was determined, using a half pitch that was then doubled to obtain the final value. The final pitch values in represent an average of at least 15 measurements. Images are reflection mode POM micrographs imaged between crossed linear polarizers. Scale bars 25 μm.

Article Snippet: We additionally used the nematic liquid crystal 5CB (4-cyano-4′-pentylbiphenyl, 95%+, Tokyo Chemical Industry) and the eutectic nematic liquid crystal blend E7 (51% 5CB, 25% 4-cyano-4′-heptylbiphenyl, 16% 4-cyano-4′-octyloxybiphenyl, and 8% 4-cyano-4′-pentyl- p -terphenyl ; Synthon GmbH) to create different CLC mixtures with variable pitch.

Techniques: