Photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on a nylon 6 substrate

The photofading of phenylazo‐aniline, ‐pyridone and ‐quinolone disperse dyes on nylon fabric was analysed using the Kubelka–Munk (K/S) spectra of fabrics exposed to a carbon arc in air. The exposure of dyed fabric through ultraviolet and coloured filters, which do not shield the main absorption band, showed a large decrease in the initial rate (K_PA) of fading. Compared with the K_PA values without filters, the values using filters were half as large for dyes without the nitro groups and a quarter as large for dyes with the nitro groups. The K_PA values may be qualitatively explained by the sum of azo scission (decrease of K/S value at λ_max) and the conversion of nitro groups to nitroso groups. These phenomena occur, respectively, via thermal disproportionation reactions between hydrazinyl radicals (from the azo group) and the reaction between hydrazinyl and N‐centred nitrosyl hydroxide radicals (from the nitro group). The azo scission is promoted by N‐centred nitrosyl hydroxide radicals via the latter reactions.     

Relationship between photofading and chemical structure of disperse azo dyes on nylon fabric†

The initial rates of photofading for 30 disperse azo dyes on nylon fabric upon exposure to a carbon arc in air have been analysed by formulating a kinetic equation that describes azo scission via the disproportionation reactions and intramolecular H‐transfer by two kinds of hydrazinyl radicals and the conversion of a nitro group to a nitroso group via the disproportionation reaction of nitrosyl hydroxide radicals. The five reaction rate constants are discussed in terms of the heats of reaction by calculating the heats of formation for the reactants, intermediates and products of each reaction using the PM5 method. Phenylazo‐ and thiazoleazo‐N,N‐substituted anilines and phenylazo‐pyridones exhibited large rate constants of multiple terms, while phenylazo‐phenols had the highest light fastness and very small rate constants for the disproportionation reactions of hydrazinyl radicals. Photofading on nylon fabric was primarily controlled by the thermal reactions of photo‐induced monohydrogenated dye radicals, which occurred via one or two primary multiple routes.     

Optical and electronic properties of 3,4‐dialkylthiophene‐based p‐/n‐alternating copolymers

Four novel highly soluble p‐/n‐poly[(2,5‐divinyl‐3,4‐dialkylthiophene)‐alt‐2,6‐pyridine] (PA₂TV‐Py) and poly[(2,5‐divinyl‐3,4‐dialkylthiophene)‐alt‐(2,5‐diphenyl‐1,3,4‐oxadiazole)] (PA₂TV‐OXD) are prepared by Heck coupling approach to compare their photoelectric properties. Characterizations of the copolymers include FT‐IR, ¹H‐NMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), UV–vis spectroscopy, photoluminescence (PL), and electroluminescence (EL). Four alt‐copolymers exhibit excellent solubility in common organic solvents (e.g., CHCl₃, THF) and good thermal stabilities, losing less than 5% on heating to ～ 250°C. The optical properties depict that the band‐gap energy of PA₂TV‐Py and PA₂TV‐OXD is similarly, ranging from 2.68 to 2.80 eV in solid film and 2.90–2.97 eV in CHCl₃ solution. PA₂TV‐Pys can emit bright turquoise light with quantum efficiencies (QE) of 30.6 and 53.9%, which about 10‐18 times higher than that of homopolymer in CHCl₃ solution. Furthermore, the QE of two PA₂TV‐OXDs (purple fluorescence) are increased to 43.6 and 68.5%, respectively, about 1.3–1.4 times higher than that of PA₂TV‐Pys. Electrochemical results indicate that the electron affinity (E_a) of four alt‐copolymers range from 2.79 to 3.09 eV, which are propitious to electrons injecting and transporting from the cathode. As a result, these novel copolymers present expected good electroluminescence(EL) performance in their single layer polymer light‐emitting device (PLED) with configuration of ITO/polymer/Al, which turn‐on voltages are between 4.0 and 5.8 V and emit bright green–yellow (538 nm) and yellow (545–552 nm) EL light. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of temporarily solubilised azo disperse dyes containing a β‐sulphatoethylsulphonyl group and dispersant‐free dyeing of polyethylene terephthalate fabric

Disperse dyes containing a β‐sulphatoethylsulphonyl group have temporary solubility and can be applied for dispersant‐free dyeing of hydrophobic fibre. Six novel temporarily solubilised azo disperse dyes having a β‐sulphatoethylsulphonyl group in their structures were synthesised, and their dyeing properties on polyester were investigated. As a dye intermediate, a diazo component having dibromo groups was prepared, and 4‐diethylamino‐4′‐(2‐sulphatoethylsulphonyl‐4,6‐dibromo)azobenzene dyes were prepared by a diazo‐coupling reaction. Then, the dyes containing dicyano groups were prepared by cyanation of corresponding dyes with dibromo groups. The absorption maxima of the dyes were affected by the substituents in the diazo and coupling component rings and varied from 434 to 616 nm in dimethylformamide. Polyethylene terephthalate woven fabric could be dyed with the synthesised temporarily solubilised dyes without using any dispersants. Dyebath pH affected the K/S value at maximum absorption as well as percentage exhaustion on polyethylene terephthalate fabric, and the optimum pH was 5. The dyes gave brownish orange, red, purple, and greenish blue hues on polyethylene terephthalate fabrics, and colour build‐up was good. Wash fastness was good to excellent, rubbing fastness was moderate to excellent, and light fastness was poor to moderate.     

Aryl and heteroaryl azo dyes derived from 6, 8‐dichloro‐4‐hydroxyquinolin‐2 (1H)‐one: synthesis,characterisation, solvatochromism and spectroscopic properties

In this research study, 6, 8‐dichloro‐4‐hydroxyquinolin‐2(1H)‐one was prepared by the thermal cyclocondensation of 2‐(2, 4‐dichlorophenylcarbamoyl) acetic acid or N, N?‐bis(2,4‐dichlorophenyl)malonamide at 140‐150°C in polyphosphoric acid, resulting in a yield of 48%. This compound was then coupled with a series of diazonium salts derived from aromatic and heteroaromatic amines for synthesis of the corresponding azo dyes. The structures of the compounds were confirmed using elemental analysis as well as ultraviolet‐visible, Fourier Transform‐infrared and proton nuclear magnetic resonance spectroscopy. The effects of organic solvents with different polarities, pH values and substituents of the diazotising components on the maximum absorption wavelength of the colorants were discussed and evaluated in detail. The acidity constants (pK_a) of the dyes were also determined using the spectrophotometric method in an ethanol‐water mixture (80:20, v/v) at 20‐23°C.     

Syntheses of an azo‐group‐bound silica initiator and silica–polystyrene composites

In this article, we present a facile method for the synthesis of an azo‐group‐bound silica (SiO₂–azo) initiator. The azo groups were introduced onto the surface of silica (SiO₂) nanoparticles via facile condensation between 4,4′‐azobis‐4‐cyanopentanoic acid and the alkyl–hydroxyl groups ‐ immobilized on the SiO₂ nanoparticle surface under ambient conditions. The polystyrene (PS) chains were grafted onto the SiO₂ nanoparticle surface by in situ polymerization with the resulting SiO₂–azo as an initiator, and then, the SiO₂–PS composite was prepared. The syntheses and properties of the SiO₂–azo initiator and the composite were characterized by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, thermogravimetric analysis, gel permeation chromatography, and differential scanning calorimetry techniques. The results confirm that the SiO₂–azo initiator and the composite were synthesized successfully. Styrene was polymerized with the initiation of SiO₂–azo, and the resulting PS domain accounted for 48.6% of the total amount of composite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Crystallographic study of two monoazo disperse dyes with a D–π–A system

Two azo disperse dyes, 2,6‐dichoro‐4‐nitro‐4′,4′‐N‐cyanoethyl‐N‐benzyl‐azobenzene ( D1 ) and 3‐(3‐methyl‐4‐N‐ethyl‐N‐benzyl‐phenyldiazenyl)‐5‐nitro‐2,1‐benzisothiazole ( D2 ), were synthesised and characterised. The crystal morphologies and single crystal structures were measured. The various packing and supramolecular interactions were described. D1 formed stellate crystals. The two benzene rings bilateral to the azo unit were not coplanar. Their dihedral angle was 75.72°. They were linked by the azo unit and were twisted. The coupling‐component N‐substituted benzyl and benzene rings were not coplanar. The chemical structure was not the typical azo structure. A dimeric packing mode was formed between adjacent molecules in a head‐to‐head and tail‐to‐tail manner. One molecule was inserted between two dimeric molecules in a head‐to‐tail manner. D2 formed globe crystals. The isothiazole and benzene rings of the azo unit were coplanar, with the typical π–π conjugated structure. The benzene rings of the azo unit and the coupling‐component N‐substituted benzyl were vertical. Their torsion angle was 179.9°.     

Novel N‐ethyl‐2‐styrylquinolinium iodides as sensitizers in the photoinitiated free‐radical polymerization of trimethylolopropane triacrylate. II

Results of kinetic studies of two‐component photoinitiator systems used in the visible‐light photoinduced polymerization of 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate are presented. Nine different styrylquinolinum dyes coupled with n‐butyltriphenylborate as a coinitiator have been used as photoinitiating systems. Reactive radicals that initiate the polymerization are formed by the well‐known mechanism of photoinduced electron transfer between dye cations acting as electron acceptors and borate anions acting as electron donors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Decolourization of textile dyes by the white‐rot fungi Phanerochaete chrysosporium and Pleurotus ostreatus

BACKGROUND: The ability of the fungi Pleurotus ostreatus and Phanerochaete chrysosporium to decolourize and detoxify 11 (mono‐, dis‐, poly‐ azo, and anthraquinonic type) dyes, widely used across the textile and leather industries, was tested. RESULTS: Different substrate specificities were revealed between P. ostreatus and P. chrysosporium in decolourization experiments. The latter fungus provided almost complete decolourization of the tested azo dyes up to 600 ppm and dis‐azo dyes up to 1000 ppm, and 80% decolourization of the tris‐azo dye DBU1L38 at 1000 ppm, after 6 days. P. ostreatus provided almost total decolourization of the anthraquinone type dye ABU62 (1000 ppm) after just 1 day. P. ostreatus also showed the ability to decolourize the tested dis‐azo and tris‐azo dyes, giving the best performances against the dis‐azo DBU1U1 (600 ppm) dye, which was 100% decolourized after 6 days. Laccases proved to be the main enzymatic activities acting in P. ostreatus decolourization. CONCLUSION: The potential of the fungi P. ostreatus and P. chrysosporium as efficient bio‐systems for decolourization and detoxification of several toxic industrial dyes was demonstrated. The role of laccases in the decolourization of dis‐azo dyes by P. ostreatus was demonstrated for the first time. Copyright © 2008 Society of Chemical Industry     

Dyeing and fastness properties of phthalimide‐based alkali‐clearable azo disperse dyes on poly(ethylene terephthalate)

The properties of a series of phthalimide‐containing azo disperse dyes and azo dyes with N‐methyl phthalimide moieties in their diazo component were investigated and compared when used to colour polyethylene terephthalate. The N‐substitution of the phthalimide gave a hypsochromic effect on the colour change and better colour yields on poly(ethylene terephthalate) fabrics, probably because of the electron‐donating property of the methyl group and the higher hydrophobicity of phthalimide‐containing azo dyes compared with those containing phthalimide moieties. The results show that phthalimide‐based azo disperse dyes have excellent dyeing fastness properties and that high wash fastness can be achieved using alkali clearance. This alternative clearance method is important for reducing the environmental impact of the dyeing process by replacing reductive clearing and, in particular, by removing the need for sodium hydrosulphite, which creates a high biological oxygen demand when released in conventional disperse dyeing effluent and which generates aromatic amines.     

A facile synthesis and tautomeric structure of novel 4‐arylhydrazono‐3‐(2‐hydroxyphenyl)‐2‐pyrazolin‐5‐ones and their application as disperse dyes

The main target of this paper was the synthesis of novel azo disperse dyes with better dyeing properties, together with a systematic investigation to determine their dominant tautomer(s) from 12 possible tautomeric structures. In this regard, novel azopyrazolin‐5‐one dyes were synthesised via the reaction of hydrazine hydrate with 2,3,4‐chromantrione‐3‐arylhydrazones. The acid dissociation constants both in the ground and in the excited state for the series prepared were determined and correlated by the Hammett equation. The results of this correlation, together with spectral data, indicated that the compounds under scrutiny exist predominantly in the keto‐hydrazo structure as a Z‐configuration, both in the ground and in the excited state. Finally, the synthesised dyes were applied as disperse dyes for dyeing polyester fabrics, and their fastness properties were evaluated. Also, the position of colour in CIELAB coordinates was estimated and discussed.     

Synthesis of novel azo‐containing polyureas derived from 4‐[4′‐(2‐hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione

4‐[4′‐(2‐Hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione ( HNAPTD ) ( 1 ) has been reacted with excess amount of n‐propylisocyanate in DMF (N,N‐dimethylformamide) solution at room temperature. The reaction proceeded with high yield, and involved reaction of both N? H of the urazole group. The resulting bis‐urea derivative 2 was characterized by IR, ¹H‐NMR, elemental analysis, UV‐Vis spectra, and it was finally used as a model compound for the polymerization reaction. Solution polycondensation reactions of monomer 1 with Hexamethylene diisocyanate ( HMDI ) and isophorone diisocyanate ( IPDI ) were performed in DMF in the presence of pyridine as a catalyst and lead to the formation of novel aliphatic azo‐containing polyurea dyes, which are soluble in polar solvents. The polymerization reaction with tolylene‐2,4‐diisocyanate ( TDI ) gave novel aromatic polyurea dye, which is insoluble in most organic solvents. These novel polyureas have inherent viscosities in a range of 0.15–0.22 g dL^?1 in DMF at 25°C. Some structural characterization and physical properties of these novel polymers are reported. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3177–3183, 2001     

Effects of a pretreatment with N‐methylmorpholine‐N‐oxide on the structures and properties of ramie

To improve the dyeing properties of ramie, the ecofriendly organic solvent N‐methylmorpholine‐N‐oxide (NMMO) was used to substitute sodium hydroxide as a ramie‐fiber swelling solvent. Through padding and baking pretreatment, ramie fabric was modified by an NMMO aqueous solution. Ultraviolet–visible spectrophotometry, Fourier transform infrared spectroscopy, X‐ray diffraction, and differential scanning calorimetry were used to investigate the effects of NMMO pretreatment on the structure of the ramie, whereas the color strength (K/S, where K is the light absorption coefficient and S is the scattering coefficient), adsorption isotherm, and dye uptake rate curve were measured to investigate the effects of NMMO pretreatment on the dyeing properties of the ramie. The results show that the ramie fiber experienced a limited and irreversible swelling because of the partial breakage of interhydrogen and intrahydrogen bonds of cellulose molecules in the amorphous area, but the crystal and chemical structure of the ramie fiber did not change obviously under the experimental conditions. The K/S value of the NMMO‐modified ramie fabrics dyed with reactive dyes increased by about 100%, and the dye uptake increased by 27.88% compared to that of the raw sample, whereas the standard affinity and diffusion coefficient value of the reactive dyes on the NMMO‐modified ramie fabric were higher than those of the raw ramie fabric. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of tetrakis‐ derivatives of bisphenol‐A with 4‐phenylazoaniline and 5‐(4‐aminophenylazo)‐25,26,27‐tribenzoyloxy‐ 28‐hydroxycalix[4]arene

The synthesis of tetrakis‐ derivatives of bisphenol‐A containing azo groups at their 2,2′,6,6′‐positions is reported. Novel examples of bisphenol‐A, coupled with diazonium salts and derived from 4‐phenylazoaniline and 5‐(4‐aminophenylazo)‐25,26,27‐tribenzoyloxy‐28‐hydroxycalix [4]arene, have been synthesized. It has been observed that the coupling reaction of diazonium salt obtained from 4‐phenylazoaniline with bisphenol‐A gives tetrakis‐ while those derived from 5‐(4‐aminophenylazo)‐25,26,27‐tribenzoyloxy‐28‐hydroxycalix [4]arene give partially substituted bisphenol‐A analogues. The newly prepared tetrakis‐azo substituted bisphenol‐A compounds ( 1 and 2 ) are characterized by using UV‐vis, FT‐IR, ¹H‐NMR spectroscopic methods as well as elemental analysis techniques. These azo compounds give rise to bathochromic shifts in the absorption spectra, which can even be detected by “naked eye.” © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Ion exchange resins for gold cyanide extraction containing a piperazine functionality, 1. Synthesis and physico‐chemical properties

The synthesis of two types of metal‐chelating resins incorporating gold‐specific piperazine groups is described. PS‐PIP is a styrene‐divinylbenzene macroporous network. MC‐PIP is a (glycidyl methacrylate)‐co‐(ethylene dimethacrylate) network. The nominal functional group concentrations are 1.84 mmol/g for PS‐PIP and 1.14 mmol/g for MC‐PIP. The proton exchange capacity is 1.95 mmol/g for PS‐PIP and 0.91 mmol/g for MC‐PIP. Accurate titration curves were used to determine pK_a values (pK_H = 7.05 ± 0.12). XPS analyses of PS‐PIP resin were followed as a function of pH (cf. Fig. 8) demonstrating that the protonation of the amine is observable by a shift in binding energy of the N (1s) peak (±1.6 eV) moving from tertiary amine form (N (1s) 399.7 eV) to the protonated tertiary amine form (N (1s) 401.3 eV). Additionally, the presence of quaternary ammonium groups was detected at a N (1s) peak at 402.3 eV (cf. Fig. 9). Metal extraction from cyanide solutions, including Brazilian mine leach solution, showed considerable preference for gold (cf. Fig. 11–12). The piperazine resins extract gold via two mechanisms: (a) ligand substitution reactions at pH > 7.05 (pK_H(a)) or (b) anion exchange reactions via the quaternary ammonium groups at high pH values. Extraction profiles were S‐shaped (cf. Fig. 10) with 50% extraction ability at pH 8.0. Cyclic experiments involving extraction, elution, regeneration and recomplexation (cf. Tab. 6 and 7) showed the ability of MC‐PIP to perform consistently at high extraction efficiencies from pH 8.6.     

N‐alkylation of chitosan by β‐halopropionic acids in the presence of various acceptors

N‐carboxyethylation of chitosan by β‐halopropionic acids in the presence of various proton and halogen ion acceptors was investigated. It has been observed that carboxyethylation of chitosan in aqueous medium is accompanied by the by‐processes of hydrolysis and dehydrohalogenation of the β‐halopropionic acids yielding β‐hydroxypropionic acid, bis(2‐carboxyethyl) ether, and acrylic acid. Degree of carboxyethyl substitution (DS) of chitosan and the relative rates of the by‐processes varied significantly depending on the conditions used and nature of the proton or halogen ion acceptor. At carboxyethylation of chitosan with the alkaline β‐bromopropionates, the DS increased in the order Cs⁺ < Rb⁺ < K⁺ ～ Na⁺ < Li⁺. For alkaline earth salts BrCH₂CH₂COOM_0.5 (M = Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), the highest DS was obtained with strontium and barium salts, which could be subsequently removed from the reaction mixture by precipitation as sulfates. Among the organic bases applied (tetrabutylammonium hydroxide, triethylamine, trimethylamine, pyridine, 4‐N,N‐dimethylaminopyridine, 2,6‐lutidine, and 1,5‐diazabicyclo[4.3.0] non‐5‐ene), the highest DS was obtained using a moderately strong base triethylamine. For the halogen acceptors (Pb²⁺, Ag⁺, Tl⁺), the stoichiometrically highest DS was achieved in a system comprising iodopropionic acid plus Tl⁺ and a comparable conversion rate was obtained using also a combination of chloropropionic acid and Ag⁺. A novel alternative preparative approach—gel‐state synthesis—was suggested that provides for the highest DS at the optimum reaction conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,Biological Activity,and Mechanism of Action of 2‐Pyrazyl and Pyridylhydrazone Derivatives,New Classes of Antileishmanial Agents

In this work, we report the antileishmanial activity of 23 compounds based on 2‐pyrazyl and 2‐pyridylhydrazone derivatives. The compounds were tested against the promastigotes of Leishmania amazonensis and L. braziliensis, murine macrophages, and intracellular L. amazonensis amastigotes. The most potent antileishmanial compound was selected for investigation into its mechanism of action. Among the evaluated compounds, five derivatives [(E)‐3‐((2‐(pyridin‐2‐yl)hydrazono)methyl)benzene‐1,2‐diol ( 2 b ), (E)‐4‐((2‐(pyridin‐2‐yl)hydrazono)methyl)benzene‐1,3‐diol ( 2 c ), (E)‐4‐nitro‐2‐((2‐(pyrazin‐2‐yl)hydrazono)methyl)phenol ( 2 s ), (E)‐2‐(2‐(pyridin‐2‐ylmethylene)hydrazinyl)pyrazine ( 2 u ), and (E)‐2‐(2‐((5‐nitrofuran‐2‐yl)methylene)hydrazinyl)pyrazine ( 2 v )] exhibited significant activity against L. amazonensis amastigote forms, with IC₅₀ values below 20 μm . The majority of the compounds did not show any toxic effect on murine macrophages. Preliminary studies on the mode of action of members of this hydrazine‐derived series indicate that the accumulation of reactive oxygen species (ROS) and disruption of parasite mitochondrial function are important for the pharmacological effect on L. amazonensis promastigotes.     

Tunable molecular weights of poly(triphenylamine‐2,2′‐bithiophene) and their effects on photovoltaic performance as sensitizers for dye‐sensitized solar cells

Despite the huge progress achieved over the past decade, the relationship between the molecular weights of dyes and the performance of dye‐sensitized solar cells (DSSCs) remains unclear. In this article, we report on the fine control of the number‐average molecular weight (M_n) of poly(triphenylamine‐2,2′‐bithiophene) (PPAT) dyes with cyanoacrylic acid moieties as acceptors. We found a correlation between the M_n and photovoltaic performance of these polymers when they were used for DSSC applications. In this study, three samples (PPAT‐01, PPAT‐02, and PPAT‐03) with different M_n values (M_ns = 1700, 2800, and 3500 g/mol) were prepared through the control of the polymerization time and characterized by analytical gel permeation chromatography and NMR. Under the same experimental conditions, the overall cell efficiency of the oligomer dyes showed a nonmonotonic tendency with increasing molecular weight. The power‐conversion efficiencies were 2.81% for PPAT‐01, 4.72% for PPAT‐02, and 1.88% for PPAT‐03. UV absorption measurements proved that PPAT‐03 formed aggregation, whereas PPAT‐01 and PPAT‐02 were in the monolayer state adsorbed on TiO₂. The larger aggregation decreased charge transfer; thus, poor photoelectric conversion performance was observed. Furthermore, a higher molecular weight reduced the amount of PPAT‐03 adsorbed on TiO₂, and this had a crucial effect on the performance of the cells because of the reduced photocurrent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44182.