# Chiral Chromonics Confined in Spherical Geometries
## 5 Induced Chiral Chromonics in Microspheres
### Chiral Induction in SSY  
The chirality induction was also studied in Sunset Yellow using PDMS as the confining matrix [50], and it was strongly dependent on the type of amino acid that was used. Figure 18 shows the textures obtained in the microspheres containing L-alanine (Figure 18a), L-lysine (Figure 18b) and trans-Hyp (Figure 18c) dispersed in a paraffin matrix. Only after doping with the high twisting power trans-Hyp, a torsion in the texture was visible at the borders of the droplet.  
Figure 16: XRD pattern of pure DSCG doped with trans-Hyp. Reprinted from [49].  
Figure 17: (**a–c**) Microsphere texture degradation. Reprinted with permission from ref. [37]. Copyright 2021, Wiley-VCH GmbH. (**d**) Free-standing PDMS film containing chromonic microspheres. Reprinted from [49].  
A richer variety of textures was observed when PDMS was used as the confining matrix. PDMS imposed an homeotropic alignment to Sunset Yellow. In the spherical confinement, this favored the formation of chiral SSY for the topologies observed only in a chiral thermotropic liquid crystal in the same type of confinement. As an example, when doping with L-lysine, toron-like structures and intermediate layer-like textures were observed (Figure 19). While doping SSY with trans-Hyp, layer-like textures and Frank-Pryce-like textures were observed.  
The XRD spectra acquired on the dried films of both SSY and SSY doped with L-lysine on the thin PDMS layers are shown in Figure 20. The XRD pattern of the pure SSY exhibited peaks related to the hexagonal mesophase. Both low and high angle peaks, which were related to the intercolumnar (17.7 A) and stacking distance (3.43 A), respectively, were visible, suggesting that the columnar structures did not have a preferred orientation, lying either perpendicular or planar on the PDMS surface.  
For SSY doped with L-Lysine, the diffraction pattern showed well-defined peaks and several features in the high angle region. This was due to the incorporation of SSY into the columnar aggregates, i.e., the presence of SSY led to an increase order in the structure. This points to the fact that the L-Lysine effect on the SSY liquid crystal phase was to shorten the rigid cylinders or increase the flexibility of the long cylinders. It is well known that SSY, as a sulfonated dye, hardly crystallizes without the presence of co-adjuvants that can help in the crystallization process [51]. In this case, L-Lysine acted as a co-adjuvant in the formation of a crystalline-like film.  
The interaction of SSY with trans-Hyp was completely different. The XRD pattern showed a residual 2D/3D SSY order for low diffraction angles (highlighted by the blue circle), while the small red lines marked the proper peaks of the trans-Hyp [52] (Figure 21).  
Figure 19: (**a**) POM images of the microspheres containing SSY doped with L-Lysine 10 wt% in PDMS, showing a toron-like texture and an intermediate layer-like structure and (**b**) SSY with trans-Hyp 26 wt%, showing a Frank–Pryce-like texture. (**a,b**) Reprinted with permission from ref. [50]. Copyright 2022, Elsevier.  
Figure 18: Sunset Yellow 30 wt% in paraffin oil doped with (**a**) L-alanine 10 wt%, (**b**) L-lysine 10 wt%, and (**c**) trans-Hyp 26 wt%. Reprinted with permission from ref. [50]. Copyright 2022, Elsevier.  
It is, therefore, clear that L-Lysine and trans-Hyp interacted with SSY in a different manner with the second mechanism of interaction being more efficient in order to induce the chirality in the system [53].