We have extended the experimental examination of layered double hydroxides of the types Mg2Al(OH)6X and Mg3Al(OH)8X, both as isotropic pellets and as oriented supported specimens, to cover the entire range from 4000 to 250 cm-1 by the use of CsI pellets and CdTe and polyethylene supports and compared our results with theoretical expectations. Close inspection of the group theoretically predicted vibrational modes for these materials shows that formal allowedness, while necessary, is not sufficient for spectroscopic intensity. The OH z-translational mode occurs around 700 cm-1, while the x,y-translations and the OH rotation (MOH bend) cover a broad region from around 1000 cm-1 down. The hydroxide O−H stretching mode, which is suppressed by orientation, is concentrated at the higher end of the total O−H stretching region. Aged material of the type Mg2Al(OH)6X shows reproducible structure around 400 cm-1 both when X is chloride and when X is 1/4ferrocyanide. This structure is weak or absent in freshly prepared Mg2Al(OH)6Cl and in both fresh and aged Mg3Al(OH)8X, strongly suggesting that local superlattice formation, required for charge avoidance when M(II):M(III) = 2:1 but not when M(II):M(III) = 3:1, is specific to the 2:1 material. We regard the inferred structural differences between fresh and aged Mg2Al(OH)6Cl as evidence for ripening by a solution−reprecipitation mechanism.

The present study indicates that a distribution of alkylammonium chain lengths in the interlayer of montmorillonite (MM) results in a greater degree of dispersion into an epoxy matrix (or possibly different polymer matrices) and improved ultimate tensile strengths. This hypothesis is supported by x‐ray diffraction (XRD) data from the modified MM clays, which clearly shows that an increase in d‐spacing does not result in an improvement in tensile strengths. Additional support is obtained from DSC analyses of the first and second heats of the treated clays which indicate that the C6 alkyl amine in a deposited (C18 + C6) alkyl ammonium mixture results in intercalation pathways for the epoxy resin. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers

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A method is presented to test whether the conversion of the mass spectrum of a polydisperse analyte to its molecular mass distribution is quantitative. Mixtures of samples with different average molecular masses, coupled with a Taylor's expansion mathematical formalism, were used to ascertain the reliability of molecular mass distributions derived from mass spectra. Additionally, the method describes how the molecular mass distributions may be corrected if the degree of mass bias is within certain defined limits. This method was demonstrated on polydisperse samples of C 60 fullerenes functionalized with ethylpyrrolidine groups measured by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; however, it is applicable to any polydisperse analyte and mass spectrometric method as long as spectrum resolution allows individual oligomers to be identified. Mass spectra of the derivatized fullerenes taken in positive ion mode were shown to give an accurate measurement of the molecular mass distribution while those taken in negative ion mode were not. Differences in the mechanisms for ion formation are used to explain the discrepancy.Official

A series of functionalized C 60 -fullerene/ epoxy nanocomposites were prepared, and their respective ultimate tensile strengths were determined. The functionalization route of the fullerenes was performed using the Prato reaction, with modified amino acids, resulting in the formation of N-pyrrolidine rings across the [6,6] junctions. Characterization of the functionalized fullerenes was done using Laser Desorption Ionization Time-ofFlight (LDI-TOF) mass spectrometry. The mechanical properties of the nanocomposites were affected by the type of modified amino acid, the degree of functional group attachment, and the consequent degree of dispersion into the epoxy matrix. A specially blended diglycidyl ether of bisphenol A (DGEBA) epoxy, having a low viscosity and high strain-to-failure was prepared by adding 1,4-butanediol diglycidyl ether to DGEBA. The lower viscosity blended epoxy allowed for easier mixing of the fullerenes.