Multi-Layered Anisotropic Films Based on the Azo Dye Brilliant Yellow and Organic Polymers

Photoalignment of an Azobenzene-Based Chromonic Liquid Crystal Dispersed in Triacetyl Cellulose: Single-Layer Alignment Films with an Exceptionally High Order Parameter

“…Based on the polar plot (Figure c), the order parameter of BY ( S ), given by S = ( A ⊥ – A // )/( A ⊥ + 2 A // ), is determined to be 0.45. This value is much higher than that reported for BY in PVP ( S = 0.3) …”

“…For instance, upon exposure to LPUV, BY molecules in polyvinylpyrrolidone (PVP) can align, whereas those in PVA hardly undergo photoalignment, where the hydrogen bonding interaction between BY and PVA molecules has been suggested to have a negative effect. Nevertheless, the best order parameter ever reported for BY in alignment films is lower than 0.3 . The key to the present achievement, in which we realized a very high order parameter (0.81), is the combination of humidification to trigger the structural reordering of BY and the use of TAC as a polymer matrix (Figure ).…”

“…Alignment films play important roles in many applications such as polarizers in liquid crystal displays (LCDs), optical modulation device, optical data storage, and polarization holography. − Conventionally, polarizers for LCDs have been fabricated by the mechanical stretching of iodine-doped poly­(vinyl alcohol) (PVA) . In the present state-of-the-art LCD technology, there is a strong demand for thin in-cell-type polarizers, , which, however, is difficult to fabricate by mechanical stretching.…”

“…In this report, we show that an alignment film with an exceptionally high order parameter (0.81) can be realized by a sequential process involving the photoalignment and humidification of an azobenzene dye, referred to as brilliant yellow (BY, Figure a), dispersed in triacetyl cellulose (TAC, Figure a) as a polymer matrix. BY is known to be a photoalignable dichroic dye ,, and behaves as a chromonic liquid crystal, a class of lyotropic liquid crystal composed of dye molecules. − The photoalignment of BY dispersed in polymer matrices has been investigated previously . For instance, upon exposure to LPUV, BY molecules in polyvinylpyrrolidone (PVP) can align, whereas those in PVA hardly undergo photoalignment, where the hydrogen bonding interaction between BY and PVA molecules has been suggested to have a negative effect.…”

Response of Optically Transparent pH Sensing Films to Temperature and Temperature Variations

“…Also in agreement with other studies [13] is the higher roughness values for ISAM films with a lower number of bilayers. The films are smooth and free of defects, unlike spin coated films of PVP and DY where the presence of the dye generated pores and depressions and increased roughness [31].…”