Mg-LDH Nanoclays Intercalated Fennel and Green Tea Active Ingredient: Field and Laboratory Evaluation of Insecticidal Activities against Culex pipiens and Their Non-Target Organisms

(1) Background: Mosquito control with essential oils is a growing demand. This work evaluated the novel larvicidal and adulticidal activity of fennel and green tea oils and their Layered double hydroxides (LDHs) nanohybrid against Culex pipiens (Cx. pipiens) in both laboratory and field conditions and evaluated their effect against non-target organisms; (2) Methods: Two types of nanoclays, MgAl-LDH and NiAl-LDH were synthesized and characterized using PXRD, TEM and SEM, whereas their elemental analysis was accomplished by SEM-EDX; (3) Results: Mg and Ni LDHs were synthesized by the co-precipitation method. The adsorption and desorption of active ingredients were conducted using LC MS/MS, with reference to the SEM-EXD analysis. The desorption process of MgAl-LDH intercalated green tea oil was conducted using ethanol, and reveled significant peaks related to polyphenols and flavonoids like Vanillin, Catechin, Daidzein, Ellagic acid, Naringenin, Myricetin and Syringic acid with concentrations of 0.76, 0.73, 0.67, 0.59, 0.52, 0.44 and 0.42 μg/g, respectively. The larvicidal LC₅₀ values of fennel oil, Mg-LDH-F, and Ni-LDH-F were 843.88, 451.95, 550.12 ppm, respectively, whereas the corresponding values of green tea were 938.93, 530.46, and 769.94 ppm. The larval reduction percentage of fennel oil and Mg-LDH-F reached 90.1 and 96.2%, 24 h PT and their persistence reached five and seven days PT, respectively. The reduction percentage of green tea oil and Mg-LDH-GT reached 88.00 and 92.01%, 24 h PT and their persistence reached five and six days PT, respectively. Against adults, Mg-LDH-GT and Ni-LDH-GT were less effective than green tea oil as their LC₉₅ values were 5.45, 25.90, and 35.39%, respectively. The reduction in adult density PT with fennel oil, Mg-LDH-F, green tea oil, and Mg-LDH-GT reached 83.1, 100, 77.0, and 99.0%, respectively, 24 h PT and were effective for three days. Mg-LDH-GT and Mg-LDH-F increased the predation Cybister tripunctatus (71% and 69%), respectively; (4) Conclusions: For the first time, Mg-LDH-GT and Mg-LDH-F was the best system loaded with relatively good desorption release to its active ingredients and significantly affected Cx. pipiens larvae and adults in both laboratory and field circumstances, and it could be included in mosquito control.     

Synthesis and Characterization of Polystyrene,Poly(butyl acrylate)-Layered Silicates Nanocomposites by Polymerization in Anionic Microemulsions

Styrene (St) and butyl acrylate (BuA) microemulsion polymerizations were investigated in presence of layered silicates (LS) and sodium dodecyl sulfate (SDS) as surfactant. Two main LS categories were used: one in the sodium form as Na montmorillonite (MMT) and the other in organomodified form LS (OLS) with quaternary ammonium salts having different hydrophobic modifiers. The swelling capacity of OLS in presence of monomers with different polarity is more pronounced for partners with closer hydrophobicity to St. The latexes obtained by microemulsion polymerization showed larger particles size for BuA polymer and BuA copolymer with sulfonated styrene than for St. Analyzing the dried hybrid polymers by XRD, we found structures which corresponds to exfoliated LS. The thermal behavior of hybrids, examined by TGA, showed higher rates of decomposing temperatures in the case of OLS, in comparison with the NaMMT hybrids. The obtained hybrids were evaluated by DLS, FTIR, DSC, and SEM.     

The influence of multiple modified MMT on the thermal and fire behavior of poly (lactic acid) nanocomposites

This work reported the preparation and physical properties of biodegradable nanocomposites fabricated using polylactic acid (PLA) and multiple organic modified montmorillonite (MMT). In order to improve the chemical compatibility between PLA and Na‐MMT, the surface of Na‐MMT was first organically modified by cetyl trimethyl ammonium bromide (CTAB) and resorcinol bis(diphenyl phosphate) (RDP) using ion‐exchange and adsorption technique. Both Fourier transform infrared and X‐ray diffraction (XRD) results indicated that CTAB and RDP molecules were intercalated into the galleries of MMT sheets to enlarge the interlayer spacing. Then, the PLA/MMT nanocomposites were prepared by a simple melt‐blending method. The XRD and TEM results of the nanocomposites indicated that the PLA polymer chains inserted into the galleries of co‐modified MMT (C‐MMT) and contained disorderedly intercalated layered silicate layers within a PLA matrix. The C‐MMT nanolayers were homogenously dispersed in PLA matrix, resulting in various property enhancement. The fabricated PLA/C‐MMT nanocomposites with 5.0 wt% addition showed significant enhancements (176%) in the storage modulus compared to that of neat PLA. The thermal stability and fire resistance were also remarkably improved. These improvements are probably because of both the physical barrier effect of the MMT nanosheets and charring effect of the C‐MMT. Copyright © 2015 John Wiley & Sons, Ltd.     

Dielectric relaxations in polyhydroxyalkanoates/organoclay nanocomposites

Two types of bacterial semi-crystalline copolyesters, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) are studied neat or with 8 wt% of Cloisite® C30B (C30B) organoclays. Wide Angle X-ray Diffraction (WAXD) and Differential Scanning Calorimetry (DSC) reveal that the nanoclays are partially intercalated, exfoliated and agglomerated. With selected sample preparation, the crystalline phase is unaffected by the C30B presence. Broadband Dielectric Spectroscopy (BDS) measurements showed no influence of the nanoclays on the secondary local relaxations modes of both polymers and on the segmental relaxation of P3HB4HB. Nevertheless, a strong modification of the α relaxation of PHBV has been observed after incorporation of C30B. A strong decrease of the fragility index and of the glass transition temperature revealed an increase of the molecular mobility in the amorphous fraction influenced by the nanoclays.     

Structure and properties of some novel fluoroelastomer/clay nanocomposites with special reference to their interaction

In the present work, rubber/clay nanocomposites were prepared by a solution mixing process using fluoroelastomers and different nanoclays (namely, Cloisite NA+, Cloisite 10A, Cloisite 20A, and Cloisite 30B). Fluoroelastomers having different microstructure and viscosity (Viton B‐50, Viton B‐600, Viton A‐200, and VTR‐8550) were used. Characterization of the nanocomposites was done by using X‐ray diffraction and atomic force microscopy. The mechanical and dynamic mechanical properties were studied. The surface energy of the clays and the elastomer was also measured. Even with the addition of only 4 phr of clay in Viton B‐50, tensile strength and modulus improved by 30–96% and 80–134%, respectively, depending on the nature of the nanoclays. Exfoliation was observed with both the unmodified and the modified clays at low loading in all the fluoroelastomers. Best properties were observed with the unmodified clay. All the grades of fluororubber followed the same trend. The increment (19%) in storage modulus was also higher in the case of the unmodified clay filled Viton B‐50 system. The results were explained with the help of thermodynamics, surface energies, and swelling studies. The difference in surface energy, Δγ, between the rubber and the unmodified clay was lower. The work of adhesion (67.63 mJ/m²) between Viton B‐50 and Cloisite NA+ was also higher than that (51.42 mJ/m²) between Viton B‐50 and Cloisite 20A. Negative ΔH_S value for the unmodified clay‐filled system thermodynamically favored the formation of the nanocomposite as compared to the modified clay filled samples where ΔH_S is positive or zero. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 162‐176, 2006     

Enhancement of Nanoclay Dispersion and Exfoliation in Epoxy Using Aminic Hardener Treated Clay

Exfoliation and dispersion of nanoclays in epoxy matrices plays an important role in achieving better physical and mechanical properties of resultant nanocomposites. In this article, modification of clay with an aminic hardener for the increment of dispersion and exfoliation into the epoxy matrix has been investigated. In the solvent media, a slurry of hydrophilic Na-Montmorrilonite was mixed and treated with isophoronediamine (IPDA). The nanocomposites containing epoxy and IPDA-modified clay were produced through a recently developed “slurry compounding” method. Dispersion and exfoliation of the modified clay and the microstructure of the resultant nanocomposite were studied by optical microscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared (FTIR) spectroscopy. The samples were then compared with the high shear mixed and sonicated nanocomposites containing commonly used quaternary ammonium modified clays. The comparison showed that dispersion and exfoliation of hardener-modified organoclays in epoxy have been improved due to the treatment of clay and the compounding method.