Proton spin thermometry and molecular dynamics of the liquid crystal PAA in the solid phase

The molecular motions in the solid phase of PAA from 77°K to the solid-nematic phase transition have been investigated using proton magnetic resonance and spin thermometry. This has shown that there are at least four dynamic processes that influence the relaxation times. Between 77 and 167 °K, the CH3 reorientation about the C3 axis is the predominate relaxation mechanism. In the region 167–238°K the rotation of the CH3 about the C–O axis and C3 axis influence the relaxation. There is also indication of proton cross relaxation to the nitrogen. In the higher temperature regions, the rotations of the molecules and diffusion are apparent in the relaxation.