The Effect of Cooling Rate and Magnetic Field on the NMR Relaxation and Thermal Behavior of [N- (p-methoxybenzylidene) -p-n- butylaniline] (MBBA)

Abstract NMR relaxation time measurements and the dsc thermal behavior of the solid state of MBBA have been examined as a function of cooling rate and aligning magnetic field. The results indicate a complicated solid state morphology as a result of these effects. Aside from the normal crystal structure, anisotropies are introduced by the aligned magnetic field and the liquidcrystalline structure that is retained on quenching to the amorphous metastable state. These anisotropies are reflected in the occurance of additional endotherms in the thermal data, and by separate relaxations for methyl reorientation in the normal crystal and the metastable amorphous material in the nmr data. The activation energies for methyl reorientation are determined.