DEFECT CHAIN MOTIONS IN THE LOW-TEMPERATURE PHASE OF MULTIPLE MIXTURES OF NORMAL-ALKANES BY MEANS OF NUCLEAR-MAGNETIC-RESONANCE SPIN-LATTICE RELAXATION-TIME MEASUREMENTS

Nuclear magnetic resonance spin-lattice relaxation time measurements in the laboratory and rotating frames, supported by differential scanning calorimetry and x-ray diffraction measurements, are reported for a series of multiple mixtures consisting of Gaussian chain length distributions of n-alkanes. The results revealed three types of molecular motions, viz., threefold reorientations of methyl groups, gauche defect motions of the chain ends of the long chains and twofold screw motions of the short chains in these mixtures. The main factor influencing the latter two motions is the width of the chain length distribution.