No abstract

No abstract

Ester-disazo dyes having per uorobutyl and diethylamino groups in their molecules have been prepared. Their absorption maxima were observed in the range l 5 483-529 nm in a liquid crystal solvent. The solubility in terms of dye structure was in the order: monoesterdisazo > trisazo > diester-disazo. The solubility of the diester-disazo dyes in terms of the substituents at the terminal end was in the order: C 4 F 9 > C 4 H 9 > H. The introduction of the 4-diethylaminonaphthylene moiety was also eOE ective in improving the solubility. The order parameter of the dye host systems was in order of the dye structures: trisazo > diesterdisazo > monoester-disazo. The order parameter for the diester-disazo dyes was calculated to be 0.79-0.82, high enough for practical use. Introductionterminal butyl groups in the molecules were calculated to be 0.66-0.81 [5]. This result indicates that the Studies of dichroic dyes are again attracting much attention due to the recent development of re ectiondichroism of polyazo dyes without polar substituents such as dialkylamino groups are not as high as would type guest-host liquid crystal displays. Azo dyes have been proposed as positive dichroic dyes for use in the be expected in spite of their slim structures. Therefore, it is supposed that the introduction of both the polar displays [1], and the improvement of the solubility and the dichroism of dyes is a challenging subject in this dialkylamino and per uoroalkyl groups into the molecule is essential to impove the solubility and dichroism of eld. Per uoroalkyl-substitute d disazo dyes have been reported to show larger solubilities than the correspondazo dyes. We report here the synthesis, solubility, and dichroism of ester-disazo dyes having per uorobutyl and ing alkyl derivatives [2], and per uoro-p-phenylene disazo dyes have also been reported to show higher diethylamino groups. solubility than the correspondin g p-phenylene derivatives [3]. Aroyloxy disazo dyes too have been reported to be 2. Results and discussion more soluble than trisazo dyes [4]. The slimmer the 2.1. Synthesis molecular structure of azo dyes, the higher the dichroism The scheme shows the synthesis of disazo dyes 7a-12a becomes and the lower is the solubility. The order extended with ester linkages. 4-Aroyloxybenzoic acids 2 parameters (S) of per uoroalkyl-substitute d disazo dyes were prepared by the reaction of 4-aroyl chlorides 1 have been reported to be higher than those of the alkylwith 4-hydroxybenzoi c acid. 4-Hydroxyazobenzene s 3-6 substituted derivatives [2], and the order parameters were synthesized by the diazotization of the arylamines of tris-, tetrakis-, and pentakis-azo dyes having two followed by coupling with phenol. Monoester-disazo dyes 7a-10a were obtained by the esteri cation of 4-hydroxyazobe nzenes 3-6 with 4-per uorobutylbenzoy l

Novel dichroic fluorescent 2-and 2,7-disubstituted perfluorophenazines exhibit emission maxima in the range 570-600 nm in MLC-2039. The order parameter of fluorescence was observed in the range 0.29-0.49.

No abstract