Proton Spin – Spin Relaxation Time in MBBA

Abstract

The proton spin-spin relaxation time of the liquid crystal, N-(p-methoxybenzylidene)-p-butylaniline (MBBA), was obtained by a modified Carr-Purcell method in the temperature range from – 110 to 65°C. The measurements were carried out both on the warming and cooling processes of the sample. Two discrete relaxation times were found in either the solid or the nematic phase of the sample. The origin of these two relaxation times was discussed on the basis of the fraction of each component. In the solid phase an anomalous temperature dependence of these two relaxation times was observed over 0 ∼ 15°C only on the warming process, and it was interpreted as an indication of the structural change toward a closer molecular packing. In the nematic phase, two relaxation times showed a different temperature dependence around 20 ∼ 25°C and then came to show a similar temperature dependence at higher temperature. This was explained in terms of a steric hindrance between adjacent MBBA molecules enhanced by the molecular alignment in the magnetic field.