Measurement of the surface-induced order in polymer dispersed liquid crystals: An approach by NMR relaxometry

A method based on NMR relaxometry is introduced to study surface-induced or der in the: isotropic phase of confined liquid crystals. We show that the m agnitude of the surface order parameter S-0 can be obtained from an increas e in the deuteron transverse relaxation rate T-2(-1). The increase originat es in the molecular diffusion between the weakly ordered surface region and disordered area in the rest of the cavity. No assumptions concerning the r esidence lime of molecules at the surface are needed. We apply the approach to a polymer dispersed liquid crystal and find a temperature independent S o of magnitude congruent to 0.08. This indicates that short range interacti ons at the interface dominate the behavior of So, and that only a partial o rientational wetting occurs. [S1063-651X(99)51205-1].