Dual-mode sorption of nonionic azo dyes by Nylon 6

Sorption isotherms of 2,4-dinitroaniline and three 4-amino-azobenzene derivatives (nonionic dyes with adequate solubility in water) on Nylon 6 (film and fiber) from water were determined at various temperatures. The observed isotherms were curved, not linear. They were very well described in terms of the dual-mode sorption model, Nernst-type partitioning, plus Langmuir sorption. The contribution of the Langmuir sorption to the total dye sorption decreased with increasing temperature. The saturation value for the Langmuir sorption increased with the crystallinity of Nylon 6 film, suggesting that the Langmuir sorption is associated with the crystalline phase.     

The in situ reactive compatibilization of nylon-6/polystyrene blends using anhydride functionalized polystyrenes

Nylon-6/polystyrene (PS) blends were reactively compatibilized by addition of various anhydride functionalized polystyrenes. The morphology of the blends was examined using a scanning electron microscopy (SEM) technique. The particle size of the dispersed styrenic phase was about 3.2 μm for the uncompatibilized 8/2 Nylon-6/PS blend while those of the compatibilized blends were decreased by as much as two orders of magnitude depending on the amount and type of the functionalized polystyrene (FPS) added. Several low-molecular weight polystyrenes with terminal anhydride groups, prepared by two different functionalization methods, were examined. The effect of molecular weight on particle size reduction depended on the basis of comparison, mass of additive, or moles of anhydride units. A high-molecular weight random copolymer of styrene and maleic anhydride was most effective when compared on a mass basis. The increase in adhesion between the Nylon-6 and the styrenic phases caused by the in situ reaction was evaluated by a lap shear technique. The free polystyrene, Nylon-6, and Nylon-FPS copolymer formed were separated by solvent extraction technique using formic acid and toluene. The extent of coupling reaction between the functionalized polystyrenes and Nylon-6 ranged from 25 to 43%. © 1992 John Wiley & Sons, Inc.     

Sorption and transport of water in nylon-6 films

Sorption and transport properties of water through films of Nylon-6 were obtained at 5, 23, and 40°C. Commercially available films were used and a Cahn electrobalance was employed for measuring the water uptake by the polymer samples. Values of the water sorption isotherms are accurately described by the Langmuir/Flory-Huggins dual-mode sorption model. At water activity values below 0.15, the volume fraction of water described by the Langmuir portion of the model was greater than the Flory-Huggins population. Solubility and diffusion coefficients of water, as well as the diffusion activation energy and enthalpy of dissolution of water for Nylon-6, were determined from the sorption experiments. Values obtained support the hypothesis of a bimodal water sorption mode, and the formation of water clusters. © 1994 John Wiley & Sons, Inc.     

The effect of water on the transport of oxygen through nylon-6 films

The effect of presence of water on the transport of oxygen through films of Nylon-6 was evaluated at 5, 23, and 40°C by permeation experiments. Through the oxygen permeability experiments it was found that the diffusion of oxygen through Nylon-6 is not a simple Fickian process and the total diffusion process can be expressed by a bimodal diffusion mechanism. Permeability, solubility, and diffusion coefficients were determined as a function of water activity for both mechanisms. The effect of sorbed water on the oxygen diffusion and solubility in the polymer is presented as a function of the state of water in the polymer and as a result of the molecular competition between water and oxygen. © 1994 John Wiley & Sons, Inc.     

Photochromic properties of thienylpyrrole azo dyes in solution

The photochromic behaviour of thienylpyrrole azo dyes in THF solutions was studied for the first time. The photochromic properties are strongly dependent on the substitution pattern on the dyes. Nitro-substituted thienylpyrrole azo dyes are particularly interesting since they exhibit very fast colouration/decolouration processes. The activation energies of these compounds are among the lowest values reported for heterocyclic azo dyes. These compounds show aggregation phenomena in freshly prepared solutions of THF, which lead to variable photochromic behaviours. Only after 1-5 h the solutions reach equilibrium and then reproducible photochromic behaviour can be observed.     

FTIR separation of nylon-6 chain conformations: Clarification of the mesomorphous and γ-crystalline phases

Specific infrared absorptions for each form of Nylon-6 have been indentified. Quenched films were prepared by melt casting and converted in turn to the α-crystalline and γ-crystalline structures. The films were examined using Fourier transform infrared spectroscopy (FTIR) with the attenuated total reflection configuration and by X-ray diffractometry. The FTIR spectrum of the pure mesomorphous component of the quenched film was calculated by subtracting away the contribution of α-crystalline peaks present due to incomplete quenching. A curve-fitting procedure was applied to the pure mesomorphous and gamma crystalline spectra. Several peaks in the mesomorphous spectrum are observed to develop a shoulder upon conversion to the γ-crystalline form. This is due to the extra gauche character imparted to the C? N bond between the methylene unit and the amide group. These and other band assignments were confirmed by analysis of model compounds.     

Delocalized cationic azo dyes containing a thiazole moiety

Several new delocalized cationic azo dyes incorporating a bathochromic thiazole moiety have been prepared in moderate to good yields. The synthesis involved the Knoevenagel condensation of an intermediate azo compound, bearing a terminal formyl group, with methylenic bases generated in situ from benzoazolium and quinolinium salts. All dyes display strong absorption around 700 nm and have shown negative solvatochromic behaviour.     

Keggin和Dawson结构多金属氧酸盐光催化脱色偶氮染料

The investigation photocatalytic degradation of three azo dyes solution(Acid Mordant Navy Blue RRN,Acid Mordant Black PV,Acid Mordant Brown RH) under UV light irradiation using the polyoxometalates as catalyst was reported in this article.The research results showed that the photocatalytic activity of Keggin catalyst is higher than that of Dawson,and the catalyst α-H4SiW12O40 had the best efficiency to the photocatalytic decoloration of RRN.In 350 mg·L-1(30 mL) RRN solution,the optimum reaction condition wa...     

Enhancement of the photochromic switching speed of bithiophene azo dyes

A series of heteroaryl substituted bithiophene azo dyes in solution were irradiated with visible light to promote the azo E-Z isomerization and then the kinetics of the thermal Z-E back reaction was studied. The speed of this process is strongly influenced by the nature of the aromatic ring linked to the NN function. While thiazole bithiophene azo dyes exhibit high switching speeds between the two isomers, but limited interconversion, for benzothiazole and substituted thiadiazole bithiophene azo dyes the switching between the two photoisomers can be performed in 3 s with a significant conversion of the trans-isomer to the thermal unstable cis-isomer (19-21%) and therefore a notable variation of the visible spectrum is observed.     

Chemical properties of water-soluble,nonionic azo compounds as initiators for emulsion polymerization

Four kinds of water-soluble, nonionic azo compounds were studied in terms of their decomposition rate and initiator efficiency in radical polymerization, and then used for emulsion polymerization. They had relatively low initiator efficiency from 0.09 to 0.46. It was attributed to the susceptibility to a cage effect, depending on their molecular size and hydrophobicity. Four azo compounds initiated emulsion polymerization but nonionic latex particles were not obtained unexpectedly. Methanol-containing medium results in the formation of a bimodal particle size distribution as well as a bimodal molecular weight distribution. © 1996 John Wiley & Sons, Inc.     

Specific features of adsorption of azo dyes on fly ash

A possibility to utilize fly ash (FA) formed at coal-fired power plants as a cheap adsorbent for the purification of wastewater containing azo dyes methylene blue (MB) and methyl red (MR) was considered. The effect of an FA additive on the adsorption capacity of active carbon was studied. The efficiency of FA as an adsorbent for the purification of aqueous solutions from MB and MR was shown. The adsorption is also fairly efficient when active carbon is partially replaced by FA. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 545–548, March, 2007.     

Morphology of Nylon-6 blends with styrenic polymers

The morphology of blends of styrenic polymers in a matrix of 75% Nylon-6 prepared in a Brabender Plasti-Corder was examined by scanning electron microscopy. Styrene/acrylonitrile copolymers (SAN) form smaller particles as the AN level increases owing to the corresponding decrease in the SAN–polyamide interfacial tension. Various styrenic polymers containing functional groups, maleic anhydride or oxazoline type, that can react with Nylon-6 during melt processing were added to the SAN phase which also led to a decrease in the particle size owing to the graft copolymer formed in situ. The effects of functional group type, amount of functional groups per chain, amount of functional polymer added, and the miscibility of the styrene/maleic anhydride (SMA) and SAN copolymers on the morphology of the styrenic phase in the Nylon-6 matrix are described. © 1992 John Wiley & Sons, Inc.     

镍铁类水滑石对偶氮阴离子染料的吸附脱色作用

采用镍铁类水滑石作为吸附剂,对偶氮阴离子染料酸性大红G、活性艳红X-3B和直接耐酸大红4BS废水进行脱色处理,研究了时间、镍与铁的物质的量之比、初始pH和无机电解质添加剂等因素对脱色率的影响,并结合红外光谱和X射线衍射分析结果讨论了其吸附脱色机理.结果表明,三种染料在镍铁类水滑石上的吸附均为层间的阴离子交换吸附和外表面的吸附.通过阴离子交换进入层间后,不同于直接耐酸大红4BS阴离子,酸性大红G和活性艳红X-3B两种阴离子与水滑石层间水分子之间产生氢键作用;在化学键合过程中,染料分子被镍铁类水滑石表面Fe3+氧化,同时偶氮键断裂导致脱色.     

Block copolyetheramides III. Blends of nylon-6 and block copolyetheramides

Blends of Nylon-6 and block copolyetheramides with hard segments of Nylon-6 and soft segments of poly(tetramethylene ether) were prepared. The impact strength of the blends was enhanced by the presence of the block copolyetheramides as compared to the Nylon-6. Different block copolyetheramides exhibited different effects on the impact strength which could be described as the difference in compatibility between the Nylon-6 and the Nylon-6 segments of the block copolymers. The difference in compatibility was verified by the investigations of TEM and DSC. As the caprolactam content of the block copolyetheramides increased, the compatibility between the Nylon-6 and the Nylon-6 segments of the block copolymers was enhanced and the blends exhibited a higher impact strength in general. The heat deflection temperature of the blends decreased as the polyether content (depending on the type and the content of the block copolyetheramide) of the blends increased. When the polyether content was ≤ or 20 wt %, a small decrease in heat distortion temperature was found. © 1994 John Wiley & Sons, Inc.     

基于QSAR对偶氮染料光响应性及降解路径研究

采用密度泛函理论方法计算偶氮染料类化合物的量子化学参数,研究该类化合物结构与光响应活性的定量构效关系(QSAR),应用多元回归方法建立的方程具有显著统计学意义,并结合紫外光谱结果进行降解过程预测.结果表明:光催化体系中会最先造成偶氮染料的N=N键与萘环的断开,然后再生成其他副产物,副产物再经过电子转移、开环等一系列反应...     

Design,synthesis, characterization,computational study and in-vitro antioxidant and anti-inflammatory activities of few novel 6-aryl substituted pyrimidine azo dyes

A series of 6-aryl substituted pyrimidine azodyes were synthesized by coupling of phenyl pyrimidine 2-amine with different aromatic amines. The synthetic compounds were screened for their in-vitro antioxidant and anti-inflammatory activities. The characterization of the synthesized compounds was carried out by IR, ¹H NMR, ¹³C NMR and Mass spectrophotometry. Computational study of designed compounds was done by OCHEM, Molinspiration cheminformatics, Datawarrior, and Swiss ADME. DPPH assay was used to determine the antioxidant activity and heat hemolysis method for anti-inflammatory activity.     

Solvent degradation of nylon-6 and its effect on fiber morphology of electrospun mats

In this work, we studied solvent-induced polymer degradation and its effect on the morphology of electrospun fibers. Nylon-6 in formic acid solvent was allowed to degrade by simply allowing it to stand for a long time, and nanofibrous mats were fabricated by taking a fraction of this solution at different time intervals via electrospinning under the same electrospinning conditions. FE-SEM images of the mats indicate that the nanofiber diameter gradually decreased with the standing time of solution, and large numbers of true nano fibers (<50 nm in diameter) were obtained. MALDI-TOF analysis revealed that the formation of low-molecular weight ions was caused by solvent degradation. FT-IR, DSC, XRD, and TGA analyses of electrospun mats showed that some physical properties, such as bond strength, crystallinity, and thermal stability also depended on solvent degradation. The obtained sub-nanofibrous mat has potential applications in different bioengineering fields.     

The dielectric properties of dry and water-saturated nylon-12

The dielectric relaxation of 30% crystalline Nylon-12 of molecular weight 20,000 has been studied at frequencies from 12 Hz to 0.1 MHz and temperatures from 77 to 375 K, and the effect of water on the relaxation spectra has been investigated. Absorbed water increases both the rate and the intensity of both its α-and β-relaxation processes and increases the rate but decreases the intensity of its γ-relaxation process. These results are interpreted in terms of the hydrogen bonding effects of water on localized motions of dipoles in Nylon-12. The relatively large half-width of the α-relaxation, which becomes better resolved at high temperatures, is attributed mainly to the random distribution of crystalline regions in the polymer. It is suggested that water lowers the steric hindrance for the localized mode of dipolar reorientation and causes a redistribution of local sites such that the β-relaxation process grows at the expense of the γ-process.     

Multimodal sorption of nonionic dyes with two amino groups by various polymers from water

Sorption isotherms of nonionic dyes with two amino groups (one anthraquinone dye and two azo dyes) on various polymers from water were measured at 40–90°C (Nylon-6 and cellulose film) and at 95°C (polyester microfiber). The isotherms were curved, convex to upward, in the range of low dye concentration C_s in water and almost linear in the range of medium to saturated C_s. The isotherms measured at low temperature (40°C for cellulose, 40–60°C for Nylon-6, and at 95°C for polyester) were satisfactorily described by considering three concurrent modes of sorption. They are Nernst type partitioning and bimodal Langmuir sorption (sorption by the higher affinity sites with a small saturation value and that by the lower affinity sites with a large saturation value). However, for the sorption of the anthraquinone dye and one azo dye by Nylon-6 film at high temperature (80–90°C), the amount of dye sorbed by the high affinity site decreased to negligibly small. Accordingly, the isotherms were expressed well by simple dual-sorption model. © 1995 John Wiley & Sons, Inc.