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