Dynamical behavior of liquid crystals containing dispersed silica particles near Sm A-N and N-phase transitions

The dynamical behavior of liquid crystal 8CB containing 2% of dispersed sil ica particles was investigated using photon correlation spectroscopy. The b ehavior differs from the one observed in the bulk. Near the phase transitio n from the nematic to the smectic A phase the orientational fluctuations of nematic director are drastically slower than in the bulk and this strongly resembles the observations in liquid crystals embedded in silica aerogel. The phase transition from the nematic to the isotropic phase is less affect ed by the presence of the silica particles but also in this case a few tent h of degree below the phase transition temperature a slowing down of the or ientational fluctuations was observed.