Cationic dyes pendant

As earlier noted, PET has no dye attachment sites for chemically active dyes. It is possible to add ionic dyeability by forming copolymers of PET with monomer species that possess active sites, for example, on a pendant side chain. The most common of these has been the incorporation of a sodium salt of a dicarboxylic acid, e.g. of 5-sulfoisophthalic acid (Figure 12.14). The acidic sulfo group allows the attachment of cationic dye molecules. If both the modified and the unmodified fibers are put into a dye bath containing a mixture of disperse and cat dyes, they will emerge with two different colors. This is useful in the creation of specialty fabrics, e.g. when two different dye types are woven into fabrics with a predetermined pattern. The multicolored pattern emerges upon dyeing. 

Where the positive charge is insulated by an alkylene link, for example, the dyes are called pendant cationic dyes e.g. Figure 2.73). 

Examples of the third type of cationic dye, with a localized pendant charge, are Basic Red 18 and Basic Blue 21 ... 

Basic Red 18 (131), Basacryl Red X-NL [14097-03-17 is an example of a pendant cationic azo dye, ia which a localized positive charge is not conjugated with the chromophoric system. /V-Kthy1-/V-(2-ch1oroethy1)ani1ine [92-49-9] reacts with trimethyl amine to form the ammonium salt coupler. The diazo component ia Basic Red 18 is 2-ch1oro-4-nitroani1ine [121 -87-9]. 

PEN blow-molded bottles, 20 50-51 Pencil leads, kaolin application, 6 688t, 696 Pencils, graphite in, 12 795 PEN copolymer bottles, 20 52 Pendant cationic azo dye, 9 423 Pendant chain polymers, fullerene,... 

The two main classes of basic dyes vary in the way in which the basic centre is built into the molecule. The use of pendant quaternary ammonium groups, where the charge is insulated from the chromogen, allows disperse dyes to be given a cationic character. Alternatively, the cationic charge is delocalised within the chromogen. 

Some anthraquinone dyes with pendant cationic groups are used commercially on acrylic and modacrylic fibres [22]. Only two disclosed structures are included in the latest revision of the Colour Index, the dyes being the reddish blue Cl Basic Blue 47 (6.54) and the greenish blue Cl Basic Blue 22 (6.55). 

Dyes with pendant cationic gronps, i.e. localised on an atom attached to the chromogen... 

The dyes bearing pendant cationic gronps are usually derived from azo or anthraquinone dyes. The azo dyes are normally made by coupling the diazo component onto a preformed cationic coupling component, exemplified by Cl Basic Blue 119 (2.46) from (2.44) and (2.45). Contrastingly, in anthraquinones the quatemisa-tion is usually carried as a post colour forming step, e.g. Cl Basic Blue 13 (2.48) from (2.47). 

Dyeing of paper has been traditionally carried out with acid, direct and basic dyes, whilst newer systems are based on cationic direct dyes. These cationic direct dyes are related structurally to reactive dyes with the labile chlorines replaced by pendant cationic groups, e.g. (2.50). 

An enormous variety of cationic azo structures have appeared in the patent literature and many of these have achieved commercial status. As previously described, they can be divided conveniently into two types depending on the location of the charge. Pendant charges can be introduced (e.g. 32) by the incorporation of a suitable aminoethyl group in a disperse type dye (69BRP1147546). 

Electrostatic self-assembly was combined with supramolecular chemistry to obtain inclusion complexes of a polymeric nonlinear optical (NLO) active dye and modified [3-cyclodextrin with induced chromophore orientation [37], The polyanion is a N,N-diallyl-aniline and sodium-2-acrylamido-2-methylpropanesulfonate copolymer functionalized with pendant azo group. The modified /i-cyclodextrin oligo-cation was obtained by treatment of hcptakis(6-dco y-6-iodo-/i-cyclodcxtrin) with excess pyridine. A linear polyamine, chitosan, was also combined with the polyanion, for comparison. Films were deposited on glass slides by dipping them alternatively in aqueous solutions of the cation and the polyanion. UV-visible spectra indicate dye aggregation and suggest the formation of an inclusion complex of the dye with the cyclodextrin, thus isolating the chromophores. 

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