Z. Fojud

MAS NMR and FTIR spectra of framework aluminosilicates

Abstract In the work, the results of 27 Al MAS NMR studies carried out for structures of different framework aluminosilicates are presented. The spectra of natural clinoptilolite and its sodium and hydrogen forms were measured. The zeolite spectra were obtained before and after incorporation of heavy metal cations (Pb 2+ , Cd 2+ , Ni 2+ and Cr 3+ ) into the zeolite structure. After decomposition of the spectra into component peaks differences caused by ion exchange were observed. Additionally, NMR spectra of kalsilite (framework aluminosilicate, not belonging to zeolite group) and other zeolites (chabazite, heulandite and analcime) were measured. 27 Al MAS NMR spectra of all the samples studied were compared with the FTIR spectra measured in the middle infrared region. Based on the results obtained it has been proved that the interpretation of spectra obtained using these two different techniques can give some information concerning changes occurring in various framework aluminosilicate structures.

Molecular dynamics in poly[(R)-3-hydroxybutyric acid] biopolymer as studied by NMR

Nuclear magnetic resonance line shapes and spin-lattice relaxation timesT1, of1H and2H nuclei of poly[(R)-3-hydroxybutyric acid] have been measured in the temperature range 100–413 K. The results provide information on the local dynamics of the compound. Activation parameters of the revealed motion are determined.

2H and 13C CPMAS NMR study of chain dynamics in n-dodecylammonium chloride

Abstract The 2 H NMR spectra of the selectively deuterated polycrystalline n -dodecylammonium chloride as well as 13 C CPMAS spectra of this compound are studied over a wide range of temperature. The results reveal a variety of phase transitions occurring in this model bilayer system and make it possible to relate them to the local molecular dynamics of the alkyl chains.

Molecular dynamics of n-dodecylammonium chloride studied by nuclear magnetic resonance

The relation between molecular dynamics and phase properties of the bilayered compound C12H25NH3C1 is studied by differential scanning calorimetry, proton second moment, and spin-lattice relaxation times. In the low-temperature phase I of the compound methyl and ammonium groups execute a classical threefold reorientation, while the alkylammonium chains are rigid on the nuclear magnetic resonance time scale. In the intermediate-temperature phase δ a trans-gauche isomerization of the alkyl chains is observed. In the high-temperature phase α the reorientation of the whole chains about their long axes, which are parallel to the normal to the ionic layer is evidenced. In the metastable ε phase the dynamics involves classical rotation of methyl and ammonium groups and CH2 groups motion of the trans-gauche isomerization type.

Polymer-Dependent Layer Structures in Montmorillonite Nanocomposites

We have studied structural differences among tetrahedral and octahedral sodium Montmorillonite layer arrangements in naturally occurring and synthetic montmorillonite clay minerals, as well as their poly(ethylene oxide) and poly(e-coprolatone) polymer nanocomposites.