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Chitosan nanoparticles (CS-NPs) and chitosan/polyacrylic acid hydrogel nanoparticles (CS/PAA-HNPs) were obtained by ionic gelation with tripolyphosphate anions and copolymerization of CS with acrylic acid (AA), respectively. The prepared NPs were loaded by different concentrations of copper (1, 2 and 3% with respect to CS) to obtain chitosan/copper nanocomposites (CS/Cu-NCs) and chitosan/polyacrylic acid/copper hydrogel nanocomposites (CS/PAA/Cu-HNCs). The prepared NPs and their NCs were characterized by different techniques. The swelling properties and copper release from CS/Cu-NCs and CS/PAA/Cu-HNCs were evaluated. The antibacterial activity of the prepared samples against bacteria (e.g., Staphylococcus aureus and Pseudomonas aeruginosa), fungi, and yeast were investigated. The results displayed that the copper release, as well as the swelling percentage of CS/PAA/Cu-HNCs, were higher than that of CS/Cu-NCs. Furthermore, the impact of using CuSO 4 , CS/Cu-NCs, and CS/PAA/Cu-HNCs as a different source of copper on chlorophyll content, vegetative growth, minerals content, and the yield of onion plants during two seasons 2016 and 2017 were studied. It was found that the yield, plant growth, and nutrient content of onion bulbs were improved using CS/PAA-HNPs, which was loaded with 75 ppm copper, as foliar spray for onion plants., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Bionanocomposites hydrogel based on conducting polymers were successfully fabricated from chitosan/polyacrylic acid/polypyrrole (CS/PAA/PPy) as well as the magnetite nanoparticle (Fe 3 O 4 -NPs) was prepared via co-precipitation method. In addition, different ratios of Fe 3 O 4 -NPs were added to the prepared bionanocomposites to enhance the antimicrobial and the electrical conductivity of the prepared conductive hydrogel. Furthermore, the morphology, the swelling percent, antimicrobial activity and the dielectric properties of the prepared conducting bionanocomposites hydrogel were investigated. The antibacterial activities of the experienced microbes were improved with the increasing the loading of Fe 3 O 4 -NPs in conducting Bio-nanocomposites hydrogel. Moreover, the DC-conductivity was examined and our resulted indicated that the DC-conductivity was enhanced by increasing the loadings of Fe 3 O 4 -NPs compared to that of the pure CS/PAA as well as CS/PAA/PPy., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This work aims to study the effect of a vinyl-modified montmorillonite (VMT) on the physical and antimicrobial properties of chitosan-graft-polyacrylic acid superabsorbent (Ch-g-PA). Ch-g-PA was first optimized using Box-Behnken design to obtain the maximum equilibrium swelling, and the model was efficient to express the experimental swelling data (R 2  = 0.999). VMT was further added to the optimized Ch-g-PA in different contents 0, 4, 7 and 10 wt%. FTIR confirmed the successful synthesis of the copolymers and their nanocomposites. Morphology and the average pores size were studied using SEM. Wide angle X-ray diffraction showed the formation of exfoliated nanocomposites after VMT addition. Thermal stability studied by TGA was greatly enhanced in the presence of VMT. The swelling kinetics by Voigt-based viscoelastic model showed that the equilibrium swelling was increased by increasing the VMT up to 7 wt% then decreased after further incorporation. The superabsorbents exhibited salt and pH-responsive properties and showed a pH-reversibility at two buffer solutions (pH = 2 and pH = 9). Moreover, the prepared superabsorbents exhibited a strong bacterial and fungal killing ability which becomes more pronounced upon increasing the VMT content. The obtained results encourage the usage of the prepared copolymer nanocomposites in many fields as antimicrobial superabsorbents of improved physical properties., (Copyright © 2018 Elsevier B.V. All rights reserved.)