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Query: UMLS:C0276640 (TEM)
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LDPE, EPM and their derivatives containing a moderate amount (0.08-1.8 by mol) of diethylsuccinate or succinic anhydryde groups were used as matrices in blending with different amount of organophilic montmorillonites and the resulting composite morphology and structure (by XRD, SEM, TEM microscopy, DSC analysis and selective solvent extraction) were studied with reference to the polar groups/MMT ratio. Exfoliated, intercalated and mixed morphologies were achieved. High concentrations of polar groups grafted to the polyolefin and montmorillonite loading not larger than 5% wt were favourable for obtaining high exfoliation degree. Particularly in the exfoliated MMT composite LDPE had lower crystallinity degree, while EPM showed increased glass transition temperature and reduced solubility in hot toluene. Moreover, oxygen and water vapor barrier property improvement was observed in films where MMT exhibits either exfoliated or intercalated morphologies. Strong interactions with the montmorillonite particle surface through the polar groups grafted to the polyolefin seems to be the basic effect responsible for the morphology and peculiar properties. A model based on the reduced mobility of the polymer located near the particle surface or inside the MMT gallery (confined phase) was proposed to explain the observed oxygen permeability reduction, the T(g) increase and solubility of poly(ethylene-ran-propylene)/MMT nanocomposites.
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PMID:Oxygen and water vapor barrier properties of MMT nanocomposites from low density polyethylene or EPM with grafted succinic groups. 1857 66

Gold nanoparticles (Au-NPs) were reproducibly obtained by thermal, photolytic, or microwave-assisted decomposition/reduction under argon from Au(CO)Cl or KAuCl(4) in the presence of n-butylimidazol dispersed in the ionic liquids (ILs) BMIm(+)BF(4)(-), BMIm(+)OTf(-), or BtMA(+)NTf(2)(-) (BMIm(+) = n-butylmethylimidazolium, BtMA(+) = n-butyltrimethylammonium, OTf(-) = (-)O(3)SCF(3), NTf(2)(-) = (-)N(O(2)SCF(3))(2)). The ultra small and uniform nanoparticles of about 1-2 nm diameter were produced in BMIm(+)BF(4)(-) and increased in size with the molecular volume of the ionic liquid anion used in BMIm(+)OTf(-) and BtMA(+)NTf(2)(-). Under argon the Au-NP/IL dispersion is stable without any additional stabilizers or capping molecules. From the ionic liquids, the gold nanoparticles can be functionalized with organic thiol ligands, transferred, and stabilized in different polar and nonpolar organic solvents. Au-NPs can also be brought onto and stabilized by interaction with a polytetrafluoroethylene (PTFE, Teflon) surface. Density functional theory (DFT) calculations favor interactions between IL anions instead of IL cations. This suggests a AuF interaction and anionic Au(n) stabilization in fluorine-containing ILs. The (19)F NMR signal in BMIm(+)BF(4)(-) shows a small Au-NP concentration-dependent shift. Characterization of the dispersed and deposited gold nanoparticles was done by transmission electron microscopy (TEM/HRTEM), transmission electron diffraction (TED), dynamic light scattering (DLS), UV/Vis absorbance spectroscopy, scanning electron microscopy (SEM), electron spin resonance (ESR), and electron probe micro analyses (EPM, SEM/EDX).
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PMID:Synthesis, stabilization, functionalization and, DFT calculations of gold nanoparticles in fluorous phases (PTFE and ionic liquids). 1969 71