Deuterium NMR of nematic droplets in a polymer matrix reveals the effect of confinement on molecular orientational ordering near the nematic-isotropic ($N-I$) phase transition. For large droplets of 0.35 μm in diameter, the $N-I$ transition is first order. For droplets of less than 0.035 μm in diameter, the isotropic phase shows a paranematic order and the $N-I$ transition is replaced by a continual evolvement from paranematic to nematic order. This result provides the first demonstration of Sheng's prediction that the $N-I$ coexistence curve terminates at a critical enclosure size.

Submicrometer-size droplets of monomeric liquid crystals dispersed in a solid polymer matrix are studied by deuterium NMR. Phase-separation processes are used to achieve droplets of a size comparable and less than the magnetic coherence length ξ∼0.5 μm, of the NMR magnetic field, 4.7 T. Selectively deuterated (4’-pentoxy- and 4’-methoxy-) 4-cyanobiphenyl compounds (5OCB-$d_2$) and (1OCB-$d_3$) deuterated in the α and methyl positions, respectively, provide for two different NMR measurement time scales to examine effects of the self-diffusion of the molecules confined to droplets. It is found that the line shape of the spectra depends on several factors which include self-diffusion, size, shape of the droplets, and type of anchoring on the droplet walls. Theoretical director configurations calculated for spherical and nonspherical droplets in the presence of an external field were used to simulate NMR spectra in the presence of self-diffusion. Effects due to external fields present during sample preparation are discussed.

We report observation of the photorefractive effect in functionalized polymer-dispersed liquid crystals. The photoconductive properties are provided by the polymer matrix, and the field-dependent refractive-index changes are generated by the dispersed nematic liquid-crystal droplets. A high diffraction efficiency (8%) and a high refractive-index modulation amplitude $\left(\mathrm{\Delta }n=2\times {10}^{-3}\right)$ are obtained in 53-$\mathit{\mu }\mathrm{m}$-thick samples with an applied field of 22 $\mathrm{V}/\mathit{\mu }\mathrm{m}$.