Dyes as guests in ordered systems: current understanding and future directions

Figures & data

Figure 1. (colour online) Schematic diagram of an alignment guest–host system showing the absorbance of light perpendicular to the director, n, and the transmittance of light parallel to the director.

Figure 2. (colour online) Schematic representation of a double layer guest–host display in the absorbing ‘off’ state (left) and in the transmitting ‘on’ state (right).

Figure 3. (colour online) Schematic diagram of the experimental set-up for measuring the polarised absorbance of an aligned guest–host sample.

Figure 4. Structure and atom numbering of the anthraquinone chromophore.

Table 1. Examples of structures from different dye classes proposed for use in guest–host systems, along with typical reported properties in nematic hosts.

		Reported properties
Dye classes	Example structures	Sϕ	Stability	Notes
Azo [7,33–37]		0.7–0.8+	Poor	High solubility
Anthraquinone [28,39,41]		0.6–0.8	Good	Low solubility
Tetrazines [45,46]		0.5–0.8	Moderate	Weak absorbance High solubility
Naphthalimides [47–50]		0.4–0.6	Good	Fluorescent
Perylenes [51,52]		≤0.7	Good	Fluorescent
Acenequinones [53]		0.7+	–	Fluorescent
Benzothiadiazoles [54]		0.7+	–	Fluorescent

Figure 5. Examples of structures from different dye classes proposed for use in liquid crystal lasers.

Figure 6. Examples of benzothiadiazole (top), anthraquinone (middle) and indigo (bottom) dye structures that exhibit thermotropic liquid crystal phases (SmA = smectic A, SmC = smectic C, N = nematic).

Figure 7. (colour online) Schematic visualisation of the orientations of the host molecules (green) the dye molecules (blue) and the transition dipole moments of the dyes (red) in a guest–host system relative to the director, n.

Figure 8. Two 1,5-diamine substituted anthraquinone dye structures and their order parameters in a nematic host.[78].

Figure 9. (colour online) A snapshot of a liquid crystal guest–host MD simulation (left) showing the dye molecules in orange and the host molecules in translucent grey. The visible TDM (red) and long molecular axis (blue) are also shown overlaid on the DFT-optimised structure of the dye (right).

Uchida T, Seki H, Shishido C, et al. Bright dichroic guest-host LCDs without a polarizer. Proc SID. 1981;22:41–46.

 Google Scholar

Matsui M, Okada S, Kadowaki M, et al. Synthesis of perfluorobutyl-substituted Ester-Disazo dyes and their application to guest-host liquid crystal displays. Liq Cryst. 2002;29:707–712. doi:10.1080/02678290210129920.

 Web of Science ®Google Scholar

Gray GW. Dyes and liquid crystals. Dyes Pigm. 1982;3:203–209. doi:10.1016/0143-7208(82)80023-5.

 Web of Science ®Google Scholar

Bahadur B. In: Bahadur B, editor. Liquid crystals: applications and uses. Chapter 11, 3. Singapore: World Scientific Publishing Co. Pte. Ltd; 1992. p. 65–208.

 Google Scholar

Saunders FC, Harrison KJ, Raynes EP, et al. New photostable anthraquinone dyes with high-order parameters. IEEE Trans Electron Devices. 1983;30:499–503. doi:10.1109/T-ED.1983.21156.

 Web of Science ®Google Scholar

Naito K, Iwanaga H. Relation between molecular structures of dichroic dyes and their solubilities in fluorinated liquid crystals. Jpn J Appl Phys Part 1. 1998;37:3422–3427. doi:10.1143/JJAP.37.3422.

 Web of Science ®Google Scholar

Pelzl G, Zaschke H, Demus D. Liquid-crystalline tetrazine compounds as dyes for guest-host displays with positive contrast. Displays. 1985;6:141–147. doi:10.1016/0141-9382(85)90081-2.

 Web of Science ®Google Scholar

Isenberg A, Krücke B, Pelzl G, et al. New liquid crystalline tetrazine derivatives for guest-host displays. Cryst Res Technol. 1983;18:1059–1068. doi:10.1002/crat.2170180814.

 Web of Science ®Google Scholar

Wolarz E, Moryson H, Bauman D. Dichroic fluorescent dyes for guest-host liquid-crystal displays. Displays. 1992;13:171–178. doi:10.1016/0141-9382(92)90027-O.

 Web of Science ®Google Scholar

Kumar S. Self-organization of disc-like molecules: chemical aspects. Chem Soc Rev. 2006;35:83–109. doi:10.1039/B506619K.

 PubMed Web of Science ®Google Scholar

Bauman D, Mykowska E, Wolarz E. Molecular orientation of perylene-like dyes in liquid crystal 8OCB. Mol Cryst Liq Cryst Sci Technol Sect. 1998;321:333–347. doi:10.1080/10587259808025100.

 Web of Science ®Google Scholar

Adamski A, Chrzumnicka E, Paluszkiewicz J, et al. Orientational order of tetra N-hexylesters of perylene and tetrachloroperylene tetracarboxylic acids in low-molar-mass liquid crystal investigated using absorption and fluorescence methods. Liq Cryst. 2014;41:768–775. doi:10.1080/02678292.2014.889232.

 Web of Science ®Google Scholar

Chen ZH, Swager TM. Synthesis and characterization of fluorescent acenequinones as dyes for guest-host liquid crystal displays. Org Lett. 2007;9:997–1000. doi:10.1021/ol062999m.

 PubMed Web of Science ®Google Scholar

Zhang X, Gorohmaru H, Kadowaki M, et al. Benzo-2,1,3-thiadiazole-based, highly dichroic fluorescent dyes for fluorescent host-guest liquid crystal displays. J Mater Chem. 2004;14:1901–1904. doi:10.1039/B402645D.

 Web of Science ®Google Scholar

Benedict JB, Freudenthal JH, Hollis E, et al. Orientational dependence of linear dichroism exemplified by dyed spherulites. J Am Chem Soc. 2008;130:10714–10719. doi:10.1021/ja802322t.

 PubMed Web of Science ®Google Scholar