A study of the dynamics of n-alkane in the rotator phase by using the pulse-field-gradient spin-echo 1H NMR method

The self-diffusion coefficient (D) and 1H spin–spin relaxation time (T2) of n-alkane, n-C24H50, were measured in the rotator and liquid phases over a wide range of temperatures by means of pulse-field-gradient spin–echo 1H NMR, in order to clarify the molecular motion of the alkane in the rotator and liquid phases. With a decrease in temperature from the liquid phase (65 to 51°C) to the rotator phase (50 to 45°C), the temperature dependence of D is abruptly changed at the transition temperature and the slope for the rotator phase is much larger than that for the liquid phase. This means that the mechanism of their diffusional processes is different. Further, it is found that the temperature dependence of the 1H T2 shows similar behavior.