Soft-stiff regime crossover for an aerosil network dispersed in liquid crystals

Hydrophilic and hydrophobic aerosil particles immersed in S-(+)-[4-(2-methylbutyl) phenyl 4-n-octylbiphenyl-4-carboxylate] or [p-(n-decyloxy) benzylidene-p-amino-(2-methylbutyl) cinnamate] compound have been studied by employing x-ray diffraction. The aerosil-induced relative layer compression Delta d has been measured in the smectic A phase as a function of aerosil concentration x. Delta d(x) is shown to sensitively monitor the intermediate-rigid transition of the adaptive aerosil network. The dominant mechanism leading to the Delta d(x) profiles is the global establishment of the aerosil-induced molecular tilt in the smectic A phase.