In this work, a polypyrrole-polyethyleneimine (PPy-PEI) nano-adsorbent was successfully synthesized for the removal of methylene blue (MB) from an aqueous solution. Synthetic dyes are among the most prevalent environmental contaminants. A new conducting polymer-based adsorbent called (PPy-PEI) was successfully produced using ammonium persulfate as an oxidant. The PEI hyper-branched polymer with terminal amino groups was added to the PPy adsorbent to provide more effective chelating sites for dyes. An efficient dye removal from an aqueous solution was demonstrated using a batch equilibrium technique that included a polyethyleneimine nano-adsorbent (PPy-PEI). The best adsorption parameters were measured at a 0.35 g dosage of adsorbent at a pH of 6.2 and a contact period of 40 min at room temperature. The produced PPy-PEI nano-adsorbent has an average particle size of 25–60 nm and a BET surface area of 17 m2/g. The results revealed that PPy-PEI nano-composite was synthesized, and adsorption was accomplished in the minimum amount of time. The maximum monolayer power, qmax, for MB was calculated using the isothermal adsorption data, which matched the Langmuir isotherm model, and the kinetic adsorption data, which more closely fitted the Langmuir pseudo-second-order kinetic model. The Langmuir model was used to calculate the maximum monolayer capacity, or qmax, for MB, which was found to be 183.3 mg g−1. The as-prepared PPy-PEI nano-adsorbent totally removes the cationic dyes from the aqueous solution.

Copolymerisation of isoprene and divinylbenzene was achieved in tolueneviaanionic chain transfer polymerization to yield highly branched polymers with good solution and rheological properties.

Hyperbranched polyisoprene was prepared by anionic copolymerization under high vacuum condition. Size exclusion chromatography was used to characterize the molecular weight and branching nature of these polymers. The characterization by differential scanning calorimetry and melt rheology indicated lower Tg and complex viscosity in the branched polymers as compared with the linear polymer. Degradation kinetics of these polymers was explored using thermogravimetric analysis via non-isothermal techniques. The polymers were heated under nitrogen from ambient temperature to 600°C using heating rates from 2 to 15°C min−1. Three kinetics methods namely Friedman, Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose were used to evaluate the dependence of activation energy (Ea) on conversion (α). The hyperbranched polyisoprene decomposed via multistep mechanism as manifested by the nonlinear relationship between α and Ea while the linear polymer exhibited a decline in Ea at higher conversions. The average Ea values range from 258 to 330 kJ mol−1 for the linear, and from 260 to 320 kJ mol−1 for the branched polymers. The thermal degradation of the polymers studied involved one-dimensional diffusion mechanism as determined by Coats–Redfern method. This study may help in understanding the effect of branching on the rheological and decomposition kinetics of polyisoprene.

In this study, Some Monoazo disperse dyes namely, 4-arylazoaminophenols (AAPs) were synthesized via diazotization and coupling reactions and later, polycondensation of these dyes with formaldehyde in the presence of aqueous oxalic acid was carried out. The resulting polymeric dyes namely, (4-arylazoaminophenolformaldehyde)s (PAAP-F)s as well as their low-molecular weight precursors were characterized by yield, melting point, color, solubility, viscosimetry, Proton Nuclear Magnetic Resonance spectroscopy, UV-visible spectroscopy and Infra red spectroscopy. Their dyeing performance on nylon and polyester were assessed using standard methods. The products were obtained in good yield and had low melting points The dyes were found to be soluble in chloroform and acetone, some were found to dissolve in ethanol and methanol, and generally insoluble in water. The dyeing on nylon and polyester had yellow shades with moderate to good light and wash fastness. Their rubbing fastnesses on nylon and polyester were very good. Polymerizations of the monomeric dyes on dyed nylon and polyester have also been carried out. The dyeing properties of the monomeric and polymeric dyes were compared with the dyes polymerized in situ on nylon and polyester and the fastness properties were found to increase on polymerization and even better with the dyes polymerized inside the fibers.

In this study, leaves of Diospyros mespiliformis was extracted using ethanol and macerated with chloroform and ethyl acetate and later screened for antibacterial  properties. The antibacterial analysis was performed qualitatively via disc diffusion method (AATCC 147) against Escherichia coli and Staphylococcus aureus as gram negative and gram positive bacteria respectively. The extract shows a significant activity on the isolated micro-organisms as evidenced by a clear zone of inhibition, more so in the ethyl acetate petri dish indicating its potentials in preventing microbial growth. The extract was then used to dye cotton fabrics by pre-mordanting, simultaneous mordanting and post-mordanting processes. The materials were assessed for fastness properties, such as fastness to washing, light, pressing and rubbing based on AATCC standards. The results show a good to moderate fastness properties suggesting that extract of Diospyros mespiliformis can be successfully used for dyeing of cotton fabric in textile industries thereby reducing the pollution and environmental hazards associated with the use of conventional synthetic chemical dyes.

ABSTRACT. Monoazo disperse polymeric dyes consisting of polyarylazocarboxybenzene-formaldehyde (PACB-F) and polyarylazohydroxynaphthalene-formaldehyde (PAHN-F) were synthesized through diazotisation, coupling and polycondensation reactions in the presence of formaldehyde and aqueous oxalic acid. The structure of the as synthesised dyes was acquired using UV-visible absorption maxima and FT-IR spectroscopy and their color, yield, melting point, solubility, and viscosity determined via standard methods. UV-visible and FTIR results showed successful formation of the polymeric dyes due to shift of wavelength of maximum absorption (λmax) (420-470 nm, 460-510 nm) and new absorption peak at around (2800-2995 cm-1) for methylene bridge, respectively. The yield of the monomeric dyes was 67.1-85.7% and polymeric 45.1-59.3%, melting point was 104.1-131.2 oC, and 136.0-143.5 oC, respectively. They are soluble in acetone, ethanol, and methanol and insoluble in n-hexane and water. The dyeing process was achieved via high temperature and carrier dyeing techniques on nylon and polyester fibers. The dyeing characteristics of the synthesised dyes were analyzed in comparison with commercial disperse dyes (terasil brilliant violet and terasil scarlet brown). The dyeing produced a very attractive hue brown shades with good to excellent washing, light, hot pressing, and rubbing fastness.                     KEY WORDS: Carbocyclic, Dyeing activity, Monoazo, Monomeric, Polymeric   Bull. Chem. Soc. Ethiop. 2021, 35(3), 485-497. DOI: https://dx.doi.org/10.4314/bcse.v35i3.2

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