A STUDY OF THE DYNAMICS OF N-ALKANE IN THE ROTATOR PHASE BY USING THEPULSE-FIELD-GRADIENT SPIN-ECHO H-1-NMR METHOD

The self-diffusion coefficient (D) and H-1 spin-spin relaxation time ( T-2) of n-alkane, n-C24H50, were measured in the rotator and liquid ph ases over a wide range of temperatures by means of pulse-field-gradien t spin-echo H-1 NMR, in order to clarify the molecular motion of the a lkane in the rotator and liquid phases. With a decrease in temperature from the liquid phase (65 to 51 degrees C) to the rotator phase (50 t o 45 degrees C), the temperature dependence of D is abruptly changed a t the transition temperature and the slope for the rotator phase is mu ch larger than that for the liquid phase. This means that the mechanis m of their diffusional processes is different. Further, it is found th at the temperature dependence of the H-1 T-2 shows similar behavior. ( C) 1998 Elsevier Science B.V.