Bifunctional Dyes Research Articles

Synthesis and spectral characteristics of fluorescent dyes based on coumarin fluorophore and hindered amine stabilizer in solution and polymer matrices

The spectral properties of novel bifunctional dyes based on – coumarin and diethylamino-coumarin and piperidine parent amine and N-oxyl and N-alkoxy derivatives were compared in cyclohexane, methanol, diethylene glycol, acetonitrile and chloroform solvents and in polystyrene, poly(methyl methacrylate) and poly(vinyl chloride) polymer matrices. The fluorescence of the derivatives excited at the longest-wavelength band around 295 nm is very low for coumarin-based dyes, whereas the fluorescence of the 7-diethylamino-3-carboxy coumarin dyes excited at 420 nm is as intense as that of anthracene in comparable conditions. Intramolecular quenching on the singlet level, monitored by fluorescence and expressed as the ratio of Φ NH/Φ NO for the parent amine and N-oxyl and Φ NOR/Φ NO for N-alkyloxy and N-oxyl, is more efficient in polymer matrices than in solvents. The spectral properties of 7-diethylamino-3-carboxy coumarin fluorophores depend on the polarity and viscosity of the environment. Highest values of quantum yield ratio were observed for 7-diethylamino-3-carboxy coumarin dyes in polystyrene and poly(vinylchloride). Though the fluorescence intensity is higher in chloroform or in poly(vinyl chloride) matrices, the intramolecular quenching efficiency of a given fluorophore by nitroxide is higher in low polarity media, such as cyclohexane and polystyrene.

O2/pH Multisensor Based on One Phosphorescent Dye

A new sensor is described based on a phosphorescent metalloporphyrin dye incorporated in a polymeric membrane, which allows measurement of the two important analytes, oxygen and pH. In such a sensor, the bifunctional dye is quenched by O(2) altering its phosphorescence intensity and lifetime (0-21 kPa O(2)), whereas protonation of the dye causes a major change in the absorption spectrum and also reduces the phosphorescence intensity. As a result, quantification and continuous monitoring of the two analytes can be achieved by (i) simultaneous phosphorescence intensity (O(2), pH) and lifetime (O(2)) measurements and (ii) parallel phosphorescence lifetime (O(2)) and ratiometric absorbance (pH) measurements. Although the first method generally requires sensor calibration in intensity mode, the second provides internal referencing and calibration-free capabilities for both analytes. This approach can be extended to sensing of some other analytes.

Dyeing of nylon 6 fabric with a bifunctional sulphatoethylsulphone reactive disperse dye

A bifunctional reactive disperse dye containing two temporarily anionic sulphatoethylsulphone groups was synthesised and applied to nylon 6 fabric by exhaust dyeing at a variety of pH levels and temperatures. A monofunctional reactive disperse dye containing one temporarily anionic sulphatoethylsulphone group was also synthesised, and its dyeing behaviour was compared with the bifunctional dye. The bifunctional reactive disperse dye exhibited high exhaustion and total fixation yield under alkaline conditions. The results also indicate that the introduction of two temporarily anionic sulphatoethylsulphone groups of the bifunctional dye gave an enhancement in dyeing performance compared with that of the monofunctional dye. The dyes also showed very good levelling and fastness properties on nylon 6 fabric.

Dyeing of nylon 6 fabric with a new bifunctional vinyl sulphone reactive disperse dye

A new bifunctional reactive disperse dye containing a temporarily anionic sulphatoethylsulphone and a nonionic disulphide bis(ethylsulphone) groups was synthesised and applied to nylon 6 fabric by the exhaust dyeing at a variety of pH and temperature conditions. A monofunctional reactive disperse dye containing only nonionic disulphide bis(ethylsulphone) group was also synthesised and its dyeing behaviour was compared with the bifunctional dye. The bifunctional reactive disperse dye exhibited high exhaustion and fixation values at pH 6 and 120 °C. The results also indicate that the combination of temporarily anionic and nonionic reactive groups of the bifunctional dye provided great enhancement in dyeing performance compared to that of the monofunctional dye. The dyes also showed very good levelling and fastness properties on nylon 6 fabric.

Photochromic behavior and its stability of a new bifunctional dye composed of spirobenzopyran and a cinnamoyl moiety

A novel bifunctional dye composed of spirobenzopyran and a cinnamoyl moiety was prepared and its photochromic behavior under the illumination of monochromatic UV light was investigated. This colorless bifunctional dye exhibits typical photochromism in both the film and in solution, through the structural and geometrical transformation from spirobenzopyran to merocyanine accompanied by a photocrosslinking reaction between the cinnamoyl moieties. Two kinds of photochemical reaction were selectively achieved by irradiation with monochromatic UV light at wavelengths of 275 and 365 nm, respectively. The effect of the selective photochemical reaction on the photochromism of the dye and its decaying behavior was investigated.

Influence of Microwaves on Nonformaldehyde DP Finished Dyed Cotton Fabrics

An alternative approach to formaldehyde-releasing conventional N-methylol com pounds is based on the use of nonformaldehyde durable press polycarboxlic acid (PCA) finishing agents. Another alternative approach, investigated here, is using microwave energy to impart durable crease resistance to dyed cotton fabric. The bifunctional dyes C.I. Reactive Red 195, C.I. Reactive Yellow 145, and C.I. Reactive Blue 221 are used in the study, and the isocratic HPLC method is employed to quantify the PCA reacted with the cellulosic material for two different curing procedures. Shade change evaluation reveals that microwave curing has a greater influence on the dE values than conventional curing. In all other aspects, primarily wrinkle recovery and deformation resistance, microwave curing offers much better results.

The Influence of Different Substitution Levels of Guar on the Quality of Viscose Prints with VS Monoreactive Dye

The basic problem of reactive printing on viscose with polysaccharide guar thickeners is the capability of dye molecule to react with the hydroxyl groups of cellulose (binding of the dye) as well as with the hydroxyl groups of water (the dye hydrolyzes) or the thickener (binding of the dye) (1, 2]. This latter is most clearly expressed in combination of the polysaccharide unmodified guar thickener and the bifunctional reactive dye where the bifunctional dye forms, due to the presence of two reactive groups, a bridge between the cellulose fibre and the guar thickener (3). The unmodified guar has a large number of free hydroxyl groups which cause crosslinking with cellulose and hinder the thickener to wash off, thus increasing the stiffness of the printing fabric. The further investigation has shown that this undesireous reaction with the guar molecules can be partly diminished by the suitable selection of chemically modified guar thickener or by lowering the dry substance content [4, 5]. In this paper the influence of nonsubstituted and different substitutited guar thickeners with monoreactive (vinylsulphone) dyes on the changing of fabric stiffness will be shown.

Kinetics of hydrolysis of monofunctional and bifunctional monochloro- s-triazine reactive dyes

The kinetics of hydrolysis of one monochloro- s-triazine and one bis(monochloro- s-triazine) reactive dye were investigated at dyeing conditions of pH 11 and temperature 80°C, and, for the monofunctional dye, also at the lower temperature of 20°C. The alkaline hydrolysis was monitored by high perfomance liquid chromatography. The pseudo-first-order rate constants of the monochloro- s-triazine dye, the bis(monochloro- s-triazzine) form and the monochloromonohydroxybis- s-triazine form of the bifunctional dye were determined and compared.

Effect of Pre-Existing Dyes and Fabric Type on Cellulase Treatment of Cotton Fabrics

Fabric weight loss through cellulase treatment of six different cottons depends on mercerization, yarn size, and fabric structure. Weight loss decreases in the order of Ne = 60 mercerized > Ne = 60 nonmercerized ≈ Ne = 40 mercerized > Ne = 40 nonmercerized knit fabrics > Ne = 20 ≈ Ne = 10 nonmercerized woven fabrics, indicating increased enzymatic hydrolysis on mercerized cotton knits with smaller yarn size. The effect of pre-existing dyes on cellulase activity is examined by measuring the difference in weight reduction for mercerized and nonmercerized cotton knits previously dyed with direct, reactive, and vat dyes. All six dyes in this study inhibit the cellulase reaction, and the degree of inhibition depends on the dye class. The concentration of dyes on fabric as estimated by K/S proves to be the most critical factor governing resulting weight losses. The planar structure of vat dyes with larger molecular sizes than indigo dye seems to play an important role in their inhibitory effect. Compared with monoreactive, direct, and vat dyes, the largest inhibitory effect is with bifunctional dyes, implying that the crosslinking property of bifunctional dyes is related to cellulase hydrolysis. This suggestion is further supported by the small reduction in weight after cellulase treatment of DMDHEU-treated cotton fabric. A model is proposed to explain the slower progress of enzymatic cleavage on crosslinked cellulose fibers.

An investigation into the reaction of bifunctional reactive dye at various pH levels

The bifunctional reactive dye Sumifix Supra Blue BRF, which has two different reactive groups (sulphatoethylsulphone and monochlorotriazine), was stored for 1 h at various pH before dyeing. Corresponding experiments were carried out with individual sulphatoethylsulphone and monochlorotriazine reactive dyes. The pH values of the solutions were set firstly by using free inorganic acid or base at 20d̀C and secondly by using various buffer solutions at 20d̀C and 60d̀C. The bifunctional dye always had relatively less unfixed dye than the corresponding monofunctional dyes at the various pH values examined. It is suggested that with this type of bifunctional reactive dyes on dyeing cellulose the sulphatoethylsulphone has the greater role to play in dye fixation.

Fixation of reactive dyes using radio‐frequency energy

Radio‐frequency (r.f.) energy has been used to increase the fixation rate of reactive dyes on cotton fabric in pad‐batch dyeing. A parallel‐plate r.f. applicator was used to heat batches of fabric containing reactive dye formulations. The time required for fixation of the dyes was reduced from several hours to a few minutes by heating the fabric in the radio‐frequency field. Reactive dyes incorporating three different types of reactive groups, vinylsulphone, nicotinic acid, and mixed vinylsulphone/ monochlorotriazine were studied and found to be applicable using the hot pad‐batch method. The colour yield and wash fastness of dyeings with the vinylsulphone/monochlorotriazine bifunctional dyes using r.f.‐assisted fixation was equal or superior to those of dyeings performed by conventional cold pad‐batch dyeing methods.

Rapid oxidation and reduction of hemoglobin at a bifunctional dye of Janus Green modified electrode

The electrochemical properties of a bifunctional organic compound, Janus Green (JG), have been investigated using spectroelectrochemistry. JG undergoes four one-electron transfer processes at the platinum electrode. An electrocatalysis of hemoglobin by JG modified electrode has been anticipate. The results show the different functions, of the azo and phenazin groups of JG. Different methods of electrode surface modification have a great effect on the electrode reaction of hemoglobin. A possible molecule orientation for JG adsorbed in a layer on a platinum electrode, is suggested. Double potential step chronoabsorptometry of hemoglobin shows that the oxidation rate of hemoglobin is much faster than the reduction one.

Rapid oxidation and reduction of hemoglobin at a bifunctional dye of Janus Green modified electrode

The electrochemical properties of a bifunctional organic compound, Janus Green (JG), have been investigated using spectroelectrochemistry. JG undergoes four one-electron transfer processes at the platinum electrode. An electrocatalysis of hemoglobin by JG modified electrode has been anticipate. The results show the different functions, of the azo and phenazin groups of JG. Different methods of electrode surface modification have a great effect on the electrode reaction of hemoglobin. A possible molecule orientation for JG adsorbed in a layer on a platinum electrode, is suggested. Double potential step chronoabsorptometry of hemoglobin shows that the oxidation rate of hemoglobin is much faster than the reduction one.

Dye‐fibre bond stabilities of dyeings of bifunctional reactive dyes containing a monochlorotriazine and a ß‐hydroxyethylsulphone sulphuric acid ester group

The dye‐fibre bond stabilities of various bifunctional dyes (commercially known as Sumifix Supra dyes) have been investigated by measuring the kinetics of dye‐cotton bond hydrolysis in aqueous buffer solution at 98d̀C. The stabilities are generally found to be somewhat higher than those of comparable monofunctional reactive dyes. Significantly better, however, is the fixation yield of the bifunctional dyes. Reasons for a very low uptake of a non‐commercial bromamine acid‐based bifunctional dye are discussed.

Crosslinking Effects in Reactive Dyeing of Protein Fibers'

Dyes featuring two reactive groups or one bifunctional group, when applied to wool and silk, can reduce the solubilities of these fibers in appropriate solvent systems. This is consistent with the formation of crosslinks during dyeing. Of the nine dyes studied, the most effective crosslinker possessed two well separated reactive groups. On wool, dyes with more closely located reactive sites were comparable in effect to formaldehyde. The reduced solubility of wool dyed with dyes containing one α-bromoacrylamide group indicates a bifunctional reaction of this group; this is in agreement with a hy pothesis stating bifunctionality. On silk, α-bromoacrylamide dyes undergo bifunctional reactions to a limited extent only, if at all. With other bifunctional dyes, the number and distribution of cnosslinks on silk depend on the type of reactive group and the method of dyeing. The inhibition of dye penetration after crosslink formation on silk in dyeings with a difluorochlo ropyrimidine dye at 40°C can be greatly alleviated by dyeing at 90°C, and thereby distributing the crosslinks more evenly throughout the fiber. The effectiveness of the highly reactive dichlorotriazine system in crosslinking depends on the method of dyeing used on wool and on silk.

Dyeing in Two Dimensions. A Review of the Use of the Monolayer Method in the Study of Dye‐Fibre Reactions

Brief reference to the origins of studies of monolayer films on water is followed by descriptions of two of the principal methods of examining their properties: the relation between film area and pressure, and the surface viscosity.Films can be produced either from actual fibre‐forming polymers, e.g. cellulose, cellulose triacetate (CTA) or models, e.g. certain proteins to represent wool, and their reactions with dyes studied. All effects of the morphology of the fibres, especially porosity, can thus be eliminated, and the actual fibre‐dye forces revealed.Three general types of film behaviour have been identified in the above type of study: Monionic dyes penetrate the film, while their ionic group remains in the water. The film is thus expanded, but becomes weaker and more compressible. Examples include monosulphonated dyes with proteins and mono‐ionic basic dyes with cellulose. Dyes with planar molecules and two or more widely spaced sulphonate groups, with cellulose or protein films, as well as disperse dyes with CTA, orientate beneath the film, with their molecules parallel with the polymer chains in the film. Direct dyes with cellulose react in this way, but the bond to the cellulose is weak, and the film viscosity is not increased. Disperse dyes form a strong bond with the CTA film, by polar forces, and increase the film viscosity. Reactive dyes or bifunctional dyes with certain strongly‐bonding groups, e.g. ‐OH, in the molecule, expand the film and greatly increase its viscosity and in certain cases form crosslinks with the polymer chains, thus strengthening the film. The application of the Gibbs adsorption equation to some of the above types of reaction is discussed.

The effect of bifunctional and monofunctional azo-dye reagents upon the oxygen-binding mechanism of human hemoglobin.

Both p‐bis‐iodoacetamido‐2,2′‐dicarboxyazobenzene and 4‐iodoacetamido‐2,3′‐dicarboxyazo‐benzene were reacted with the accessible SH‐groups of human hemoglobin tetramers. The mono‐functional azo dye produced the expected, and uniformly modified hemoglobin, in which both cysteines‐β93 were alkylated. The bifunctional dye gave rise mainly to a symmetrically modified hemoglobin, forming cross‐links within the two β‐chains between cysteine‐93 and lysine‐82. A small amount of a second, asymmetrical hemoglobin derivative could be isolated, carrying the same cross‐link in one β‐chain, while the second cross‐link ran from one cysteine‐β93 to the histidine in position 45 of the neighbouring α, chain. Homotropic cooperativity of oxygen binding was reduced in all these derivatives of hemoglobin. Both cross‐linked hemoglobins possessed an oxygen‐binding curve with a Hill coefficient of 1.0–1.2. For the hemoglobin reacted with mono‐functional dye this coefficient varied between 1.65 and 1.72. Its Bohr effect amounted to 0.3, while the cross‐linked hemoglobins showed no Bohr effect.