Rigidified merocyanine dyes with different aspect ratios: Dichroism and photostability

• We synthesized new rigidified merocyanine dyes.
• Improvement of dichroic ratio of a guest/host system by varying the matrix.
• Increase of the photostability by alignment in a matrix.
• Proof of suitability of the dyes as thin layer polarizers and guest/host displays.

A series of new rigidified merocyanines were investigated with regard to their optical properties as dichroic dyes. Guest/host-mixtures of the dyes were prepared using a liquid crystal and a reactive mesogen mixture. Their dichroism was studied using linearly-polarized UV/Vis-spectroscopy. A strong dependence of the dichroic ratio on the aspect ratio, the number of double bonds in the molecular structure, and on the maximum wavelength of absorption was found. A strategy to increase the aspect ratio has also been demonstrated. Additionally, the photostability was characterized using continued irradiation with polychromatic light from a xenon source. High photostability was found in all host mixtures in the absence of oxygen by alignment in a matrix. The suitability for their application as dichroic dyes in thin layer polarizers and guest/host-displays is herein discussed.

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