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The surface compositions of polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends have been investigated using x-ray photoelectron spectroscopy (XPS). The XPS results demonstrate that there are significant differences between the composition of the surfaces (e.g., outmost ∼6 nm) and the bulk of both miscible and immiscible blends. The surfaces of PS/PVME films dip-coated from either toluene or trichloroethylene solutions are found to be enriched in PVME. An additional enrichment in the PVME content of the surface is also observed when miscible PS/PVME blends are phase separated by heating them above the lower critical solution temperature. The average composition profile of a miscible 50/50(w) blend has been obtained by angular-dependent XPS measurements. This experiment suggests that the enrichment is the result of a concentration gradient rather than a monolayer coating. These results are discussed in terms of the surface free energies of PS and PVME and the degree of mixing in the surface layer.

The direct depolymerization of SiO2 to distillable alkoxysilanes has been explored repeatedly without success for 85 years as an alternative to carbothermal reduction (1900 °C) to Si(met) , followed by treatment with ROH. We report herein the base-catalyzed depolymerization of SiO2 with diols to form distillable spirocyclic alkoxysilanes and Si(OEt)4. Thus, 2-methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, or ethylene glycol (EGH2) react with silica sources, such as rice hull ash, in the presence of NaOH (10%) to form H2O and distillable spirocyclic alkoxysilanes [bis(2-methyl-2,4-pentanediolato) silicate, bis(2,2,4-trimethyl-1,3-pentanediolato) silicate or Si(eg)2 polymer with 5-98% conversion, as governed by surface area/crystallinity. Si(eg)2 or bis(2-methyl-2,4-pentanediolato) silicate reacted with EtOH and catalytic acid to give Si(OEt)4 in 60% yield, thus providing inexpensive routes to high-purity precipitated or fumed silica and compounds with single Si-C bonds.

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For carbon nanotube-based electronics to achieve their full performance potential, it is imperative to minimize the contact resistance between macroscale metal contacts and the carbon nanotube (CNT) nanoelectrodes. We have developed a three-dimensional electrode platform that consists of carbon nanofibers (CNFs) that are directly grown on a metal contact, such as copper (Cu). Carbon nanofiber morphology can be tailored by adjusting the annealing time of a thin electrochemically deposited nickel catalyst layer on copper. We demonstrate that increasing the annealing time increases the amount of copper infused into the nickel catalyst layer. This reduces the carbon deposition rate, and consequently a more well-defined CNF 3D architecture can be fabricated. This direct growth of CNFs on a Cu substrate yields an excellent electron transfer pathway, with contact resistance between CNFs and Cu being comparable to that of a Cu-Cu interface. Furthermore, the excellent bonding strength between CNFs and Cu can be maintained over prolonged periods of ultrasonication. The porous 3D platform affixed with intertwined CNFs allows facile surface functionalization. Using a simple solution soaking procedure, the CNF surface has been successfully functionalized with iron(II) phthalocyanine (FePc). FePc functionalized CNFs exhibit excellent oxygen reduction capability, equivalent to platinum-carbon electrodes. This result demonstrates the technological promise of this new 3D electrode platform that can be exploited in other applications that include sensing, battery, and supercapacitors.

Self-assembled solution micelles prepared from polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP), have been employed as templates to synthesize copper nanocatalysts which are regarded as an excellent catalyst system for 1D nanomaterial synthesis. We have demonstrated that uniform-sized nanoparticles with diameters ranging from 1 to 15 nm have been generated. We have revealed that nanocatalyst size can be rationally tailored by adjusting the interaction between copper precursors and ligands and metal sequestration time. Ordered arrays of copper nanocatalysts derived from depositing a monolayer of solution micelles exhibit excellent thermal stability and do not agglomerate during the thermal treatment at 850°C, typical growth temperature for 1D nanomaterial using the chemical vapor deposition technique. High-density and aligned single-walled carbon nanotubes with uniform diameter have been synthesized using the chemical vapor deposition technique. The average diameter is 1.4 nm, which is on the same order of catalyst size, around 2.0 nm. The combination of tunable size and spacing with superb thermal stability and outstanding catalytic activity offered by this new copper nanocatalyst system will enable growth of high-yield 1D nanomaterials with controllable diameter and spacing consistently and reproducible properties. It also paves a new path to study the effect of nanocatalyst size on 1D nanomaterial synthesis and their properties.

The B(C 6 F 5 ) 3 catalyzed Piers-Rubinsztajn (oxysilylation) reaction of the cubic symmetry Q-cage [(HMe 2 SiOSiO 1.5 ) 8 ] with ethoxysilanes in hexane forms microporous 3-D networks coincident with ethane evolution. Slow drying provides monoliths whereas fast drying provides powders. The reaction is most efficient if initiated at 60°C for 5 min and then allowed to progress at ambient. The products offer high specific surface areas [SSAs > 700 m 2 /g, e.g. with Si(OEt) 4 ], with micropores of 0.62.0 nm, mesopores of 240 nm, total pore volumes µ 0.5 cc/g, and thermal stabilities to 320°C. Changes in reaction conditions (times, solvent volumes, catalyst concentrations) do not significantly change product properties pointing to rapid and complete reaction as evidenced by the near absence of residual SiH under all conditions for 1:1: SiH:SiOEt ratios. RSi(OEt) 3 gives similar 3-D microporous gels. Smaller R groups give higher SSAs than those with large R groups; however, R = n-octyl is not porous. Rigid, bridged compounds [(EtO) 3 SiRSi(OEt) 3 ] (R = phenyl, biphenyl) offer high SSAs whereas flexible bridges [R = (CH 2 ) 2 or 8 ] give reduced SSAs. All materials were characterized by FTIR, TGA, XRD and BET. XRD studies show periodicities suggesting some long range ordering as might be expected for reactions with cubic symmetry Q 8 cages. However, the fast reaction rates likely generate kinetic rather than thermodynamic products that cannot be expected to exhibit high degrees of ordering. Gel affinities for specific organics were studied showing some preferential ability to absorb specific solvents for example the 1:1 OHS:vinylSi(OEt) 3 gels were more selective for toluene than the 1:1 OHS:TEOS gels.

The direct depolymerization of SiO 2 to distillable alkoxysilanes has been explored repeatedly without success for 85 years as an alternative to carbothermal reduction (1900 8 8C) to Si met ,followed by treatment with ROH. We report herein the base-catalyzed depolymerization of SiO 2 with diols to form distillable spirocyclic alkoxysilanes and Si(OEt) 4 .T hus,2methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, or ethylene glycol (EGH 2 )r eact with silica sources,s uch as rice hull ash, in the presence of NaOH (10 %) to form H 2 Oa nd distillable spirocyclic alkoxysilanes [bis(2-methyl-2,4-pentanediolato) silicate,bis(2,2,4-trimethyl-1,3-pentanediolato) silicate or Si(eg) 2 polymer with 5-98 %c onversion, as governed by surface area/crystallinity.S i(eg) 2 or bis(2-methyl-2,4-pentanediolato) silicate reacted with EtOH and catalytic acid to give Si(OEt) 4 in 60 %y ield, thus providing inexpensive routes to high-purity precipitated or fumed silica and compounds with single SiÀCb onds.