Deuterium NMR of a pentylcyanobiphenyl liquid crystal confined in a silica aerogel matrix

The temperature dependence of the deuterium NMR line shape was studied in a pentylcyanobiphenyl (5CB) nematic liquid crystal embedded into lecithin-treated and nontreated continuous-pore silica aerogel matrices. In the lecithin-treated matrix the temperature dependence of the NMR absorption spectra of 5CB exhibits a pronounced first-order nematic-isotropic transition, while in the nontreated matrix only a weak discontinuity was found. The observed almost continuous onset of nematic ordering in the latter case appears to be due to the spread of nematic-isotropic-transition temperatures T NI , in different aerogel cavities