Michael M. Lerner

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.

Graphite intercalation of bis(trifluoromethanesulfonyl) imide and other anions with perfluoroalkanesulfonyl substituents

Abstract Graphite intercalation compounds (GICs) containing the bis(trifluoromethanesulfonyl) imide anion, C x N(SO 2 CF 3 ) 2 , were prepared under ambient conditions in 48% hydrofluoric acid, using the oxidant K 2 MnF 6 . Within seconds, the graphite phase was no longer observed, and a stable, stage 2 product with x = 37 and d i = 8.1 A was obtained in 15 min. Product compositions were evaluated by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and elemental analyses. One-dimensional structural refinement for the stage 2 product provided values for the graphene carbon/intercalant molar ratio, distance between graphene and sulfonate oxygen planes, and the anion orientation within the intercalated galleries. Intercalation reactions with the larger fluoroanions bis(pentafluoroethanesulfonyl) imide (CF 3 CF 2 SO 2 ) 2 N − , trifluoromethanesulfonyl- n -nona-fluorobutanesulfonyl imide (CF 3 SO 2 )(CF 3 (CF 2 ) 3 SO 2 )N − , and tris(trifluoromethanesulfonyl) methide (CF 3 SO 2 ) 3 C − occurred but were dramatically slower. For each product, stages and d i were determined for the mixed phase products. In all cases with the larger anions, the products obtained also contained unreacted graphite.

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.

Electrochemical Preparation of Graphite Bis(trifluoromethanesulfonyl) Imide

Graphite intercalation compounds (GICs) containing bis(trifluoromethanesulfonyl) imide, N(SO 2 CF 3 ) 2 , are prepared for the first time by electrochemical oxidation of graphite. Electrolytes with nitromethane and ethyl methyl sulfone are used to prepare GICs up to stage 1. The potential charge curves under galvanostatic or pulse-charge mode show transitions associated with GIC staging, and charge and discharge capacities and charging efficienices are reported at transition points. The stage I GICs have not been prepared before and rapidly decompose in air in the electrolyte. GIC gallery heights and stages are determined by powder X-ray diffraction, and the stage 1 composition is determined by thermogravimetric analysis. Structural and electrochemical properties are compared with those for related GICs.

Rapid exfoliation of a layered titanate by ultrasonic processing

The application of ultrasound dramatically increases the rate of exfoliation of HxTi2−x/4O4·yH2O (H–Ti) in the presence of aqueous tetrabutylammonium (TBA) hydroxide. The effect of ultrasonication power and processing time on particle size distributions are evaluated. Applied powers of 60–300 W and reaction times of 2–30 min effectively reduce the H–Ti particle size to <100 nm. Both particle size distribution analysis and UV–Vis spectroscopy were used to study the effect of ratio of TBA ion to exchangeable protons in H–Ti; a minimum ratio of TBA/H≥0.5 is required for rapid exfoliation.