Christopher Oriakhi

Incorporation of poly(acrylic acid), poly(vinylsulfonate) and poly(styrenesulfonate) within layered double hydroxides

Poly(acrylic acid), poly(vinylsulfonate) and poly(styrenesulfonate) have been incorporated between the positively charged sheets of layered double hydroxides (LDHs)M1–xAlx(OH)2+(M = Mg, Ca, Co) and Zn1–xM′x(OH)2+(M′= Al, Cr) to form layered nanocomposites. The resulting nanocomposites contained the LDH sheet structures separated by 7.6–16.0 A, which is sufficient to accommodate polymer bilayers between the LDH sheets. Preparations were carried out in deaerated aqueous base by a template reaction, involving the formation and precipitation of nanocomposites from metal nitrate-salt precursors in the presence of the dissolved polymer. Structural and compositional details were provided by X-ray diffraction (XRD), FTIR spectroscopy, elemental analysis, differential scanning calorimetry (DSC) and thermogravimetry (TG). Scanning electron microscopy (SEM) indicates that the nanocomposition of LDHs with ionomers significantly alters the particle microstructure from that of the LDH carbonates derived from aqueous precipitation.

Surface and interfacial properties of polymer-intercalated layered double hydroxide nanocomposites

The surface and interfacial properties of the layered double hydroxide (LDH) phase Mg6Al2(OH)16CO3·4H2O (LDHCO3) and its nanocomposites with poly(styrenesulfonate) (LDHPSS) and poly(vinylsulfonate) (LDHPVS) were characterized by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, He pycnometry, and electrophoretic light scattering. Polymer incorporation within the inter-gallery space resulted in a shift of the d003 reflection from 7.7 A (LDHCO3) to 12.7 A (LDHPVS) and 21 A (LDHPSS). This increase in basal plane spacing caused the density of the LDH samples to decrease from 2.05 g/cm3 (LDHCO3) to 1.83 and 1.41 g/cm3 for LDHPVS and LDHPSS nanocomposites, respectively. LDHCO3 exhibited a positive electrophoretic mobility over the pH range from 4–11 with an isoelectric point (iep) at pH 11. However, the LDH nanocomposites displayed a negative electrophoretic mobility over the measured pH range, indicating that the surface properties of the LDH nanocomposites were dominated by negatively charged sulfonate groups from adsorbed polymer molecules.

Poly(pyrrole) and poly(thiophene)/claynanocomposites via latex-colloid interaction

Abstract Preformed poly(pyrrole) and poly(thiophene) are incorporated into montmorillonite by the interaction of colloidal nanoparticles of the polymers with the colloidal, exfoliated host. Nanocomposites obtained are characterized by X-ray diffraction, SEM, FTIR, and electrical conductivity. The colloid — colloid reaction method provides a general route to incorporation of intractable polymers within layered host structures that can be exfoliated, such as smectite clays, metal disulfides, and some metal oxides.

Preparation of nanocomposites containing poly(ethylene oxide) and layered solids

Abstract Single-phase nanocomposites containing montmorillonite, MoS2, MoO3 or TiS2 with poly(ethylene oxide) are obtained by the exfoliation of the layered solid, adsorption of polymer, and subsequent precipitation of solid product. Aqueous solutions can be employed for these syntheses except PEO/TiS2, which is prepared from lithiated TiS2 in an N-methyl formamide (NMF) solution. X-ray diffraction indicates that the resulting solids increase in basal-plane repeat by approximately 4 or 8 A, consistent with the incorporation of a single or double layer of polymer between inorganic layers. Reaction stoichiometries and elemental analyses provide compositions for the single-phase products.

Intercalation chemistry of cobalt and nickel dioxides: A facile route to new compounds containing organocations

A simple chemical method is reported for the intercalation of layered nickel or cobalt dioxide with organocations. Compounds containing anilinium, dodecyltrimethylammonium, octadecyltrimethylammonium, or distearyldimethylammonium cations are obtained by reaction of lithiated hosts with aqueous persulfate, followed by treatment with the desired organocation. Basal-repeat distances for the intercalated products indicate that the arrangements of organocations are similar to those seen with other layered hosts, with bilayers of alkylammonium ions, or a single layer of anilinium, in the pillared galleries. Thermogravimetric and elemental analyses are used to estimate compound stoichiometries, and indicate the partial exchange of organocation for lithium. The anilinium compound contains oligomeric cations, and is unstable when treated with polar solvents. Open circuit measurements indicate that the materials contain Co in an oxidation state of 3+ or higher.

Preparation of layered nanocomposites of PEO with MnPS3, CdPS3, and MoO3 by melt intercalation

Abstract Intercalated nanocomposites comprised of polyethylene oxide (PEO) and MPS 3 (M = Mn, Cd) or MoO 3 are prepared by the direct heating of the alkali-metal intercalated host with PEO. This process, known as melt intercalation, has previously been applied to polymers with layered silicates. Reaction rates and yields are low below the melting temperature for PEO, but at 125°C a significant or quantitative conversion to the ordered nanocomposite can be achieved in 5–30 h. Intercalated nanocomposite yields are followed by powder X-ray diffraction to provide relative reaction rates at 50, 75, and 125°C for PEO with M w = 1 × 10 5 and 5 × 10 6 .

Synthesis and luminescence properties of a poly(p-phenylenevinylene)/montmorillonite layered nanocomposite

A layered nanocomposite of poly(p-phenylenevinylene) (PPV) with montmorillonite clay is prepared at ambient temperature by incorporation of poly(p-xylylenedimethylsulfonium) (PXDMS) into the montmorillonite galleries, followed by the base-mediated elimination of dimethylsulfide. Powder X-ray diffraction on the intermediate and final product show gallery expansions of 5.5 and 4.6 A, respectively, indicating the nanoscale ordering of polymer and montmorillonite layers. Thermogravimetric analyses of the products indicates the loss of approximately 75% of the sulfonium groups by reaction with base. Luminescence measurements show a shift in emission peak intensities indicating the conversion of PXDMS to PPV within the montmorillonite galleries.

Preparation of nanocomposites of linear poly(ethylenimine) with layered hosts

Nanocomposites are prepared with the layered hosts Na-montmorillonite, MoS2, MoSe2, TiS2, TaS2, MoO3, and MPS3 (M = Mn, Cd) incorporating linear poly(ethylenimine) (LPEI) by reaction of the colloidal host and LPEI in aqueous solution. The products exhibit lattice expansions along the stacking direction of 3.9–4.7 A and polymer contents of 13–18 mass percent, consistent with the formation of a single adsorbed monolayer of LPEI between host sheets. FTIR spectroscopic analyses indicate a low degree of protonation for the included polymer. Impedance data indicate that the bulk ionic conductivity of Na-montmorillonite increases by several orders of magnitude upon incorporation of LPEI.