Azo-dye attached polymers

Matsumoto, S., Kubodera, K., Kurihara, T., and Kaino, T., Nonlinear optical properties of an azo dye attached polymer, Appl. Phys. Lett., 51,1, 1987. 

Main Chain Polymers. Another system of dye attached polymers is a polyamic acid and a polyimide with a Tt-electron conjugation in the main chain. The Tt-electron conjugated system is not an intramolecular charge transfer system, unlike the azo and stilbene dye mentioned above. The polyamic acids (PAAs) were obtained through the reaction of a carboxylic acid anhydride and a diamine. A Tt-electron conjugated system exists in the diamine compound. These polyamic acids were soluble in conventional solvents and... 

Figure 4. Ghemical structure of azo-dye attached EO-polymers and their wavelength dependent...

This modest improvement in stability is not as great as that observed in azo dyes sized similarly to 8 covalently attached to PMMA, which lose 10% of their alignment initially, and then only 10%/yr afterwards. (15) The covalent attachment of longer dyes to polymers might therefore lead to materials stable enough for testing in a particular setting over a period of years. 

Upon ultraviolet irradiation, trans CHP isomerized to the cis form (around 10%), and the aqueous solution viscosity decreased as much as 80%. The conformation change was interpreted as follows. The anionic linear and planar eA -trans CHP would attach itself to the hydrophobic poly(methacrylic add) backbone, teading to an extended polymer conformation. In the cis form, azo-dyes are much more hydrophilic. Consequently, the cis form was envisaged as binding less strongly so that the polymer chain would be less extended. 

Because azo dyes, as amaranth, are the most widely used food colorants and are water soluble, they were bonded to selected polymers via a sulfonamide linkage. However, the azo linkages in the dyes themselves were unstable to intestinal microbial action and do not meet the requirements of biological stability because they are cleaved in the gut to yield absorbable aromatic amines. Hence a variety range of chromophore classes have been reported to be incorporated into polymers. For the anthraquinone class of chromophores, the basic water insolubility was changed by converting a portion of the backbone to sulfonic acids that impart anionic solubilizing functions. However, this meant that fewer chromophores could be attached and less intense colors would result. 

Egawa has taken a novel approach to use the N-B interaction to influence the color of azo dyes 47 and 48 on saccharide binding. The ortho boronic acid systems show substantial changes in the UV-vis absorption spectra on saccharide binding. The same system has also been attached to a poly(ethyleneimine) polymer. ... 

Recently azo dyes have been attached to polymer backbones to make oligomeric type dyes. Problems with this type of colorant arise as you are adding as much of the polymer as you are of the dye. 

It will be seen that all the direct dyes so far discussed are extended, linear molecules—a characteristic of the class. It has been shown that the distance between the two azo groups in a substantive dye is 1.08 nm and that of the polymer unit length in cellulose is 1.03 nm, so that the operation of van der Waals forces is facilitated, though there is clear proof that this is not the only factor present since substantivity disappears in CA and CT fibres. H-bonding is invoked as a source of attachment, the hydrogen atoms of—OH groups in the cellulose unit bonding with N of an azo link... 

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