Influence of Confinement on Relaxation of Director Orientational Fluctuations in Nematic Liquid Crystal.
Arroyo Félix, Edwin X.
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Dynamic light scattering (DLS) was applied to study the influence of confinement on dynamic properties of 4-methoxybenzylidene- 4- butylaniline (MBBA) nematic liquid crystal dispersed in random porous matrices with mean pore sizes of 10 and 100 nm. In DLS experiments we observed for confined MBBA in 100 nm random pores at nematic phase two relaxation processes. The first relaxation process is attributed to bulk like orientational fluctuations of director in the portion of liquid crystal located in the central part of the pores. The second process is associated with fluctuations of director orientational fluctuations in liquid crystal at pore wall - liquid crystal interface. This second relaxation process is slower than the first relaxation process. For confined MBBA in 10 nm random pores in nematic phase a slow and a broad relaxation process is present which is absent in the bulk nematic liquid crystal. The result obtained for MBBA confined in random porous matrices suggested that the main differences in the dynamical behavior from that of bulk are due to the existence of the liquid crystal pore-wall interface and the slow process is surface related relaxation.