Phase behavior of the liquid crystal 8CB in a silica aerogel

Light scattering and precision calorimetry show that the nematic ordering of octylcyanobiphenyl (8CB) filling the connected network of pores of a silica aerogel does not occur via the first-order phase transition characteristic of the bulk. Rather, ordering is continuous with an orientational correlation length never increasing beyond the aerogel pore size. The heat-capacity anomly of the second-order nematic--smectic-A phase transition seen in the bulk is absent or greatly broadened in the aerogel.